A sociogram for the cranes of the world · sociogram (sensu Wilson, 1975), a description of all social displays, together with higher level be-havior sequences, here termed activities

Behavioural Processes 43 (1998) 125–151

A sociogram for the cranes of the world

David H. Ellis a,*, Scott R. Swengel b, George W. Archibald b, Cameron B. Kepler c

a Patuxent Wildlife Research Center, U.S. Geological Sur6ey, Biological Resources Di6ision, U.S. Department of the Interior,HC 1 Box 4420, 3722 Defiance Street, Oracle, AZ 85623, USA

b International Crane Foundation, E-11376 Shady Lane Road, Baraboo, WS 53913-9778, USAc Patuxent Wildlife Research Center, 400 Snapfinger Dr., Athens, GA 30605, USA

Received 7 May 1997; received in revised form 11 December 1997; accepted 19 December 1997

Abstract

The behavioral repertoire for the world’s 15 species of cranes includes over 100 behavioral acts with clear socialsignificance. Each species performs at least 60 discrete social postures, vocalizations, displays, and activities. Becauseall but a handful of the stereotyped social displays are common to all species, the presence or absence of socialdisplays was useful only to a limited degree in comparing the relatedness of established crane taxonomic groups.However, the breadth of the repertoire for each species and for the family Gruidae tentatively places cranes at theapex of social complexity (at least for stereotyped displays) in the animal world. © 1998 Elsevier Science B.V. Allrights reserved.

Keywords: Crane; Gruidae; Social behavior

1. Introduction

This study is based on observations of captivecranes of all species (Table 1), with supplementalobservations of all species in the wild. Previousstudies of the social repertoire of cranes include:the classic ethogram of the red-crowned crane byMasatomi and Kitagawa (1975), and Masatomi’s(1983a) work detailing copulatory sequences inGrus species of cranes. Archibald (1976a) used

social displays, especially the Unison-call (a formof antiphonal duet) in an attempt to deciphercrane phylogeny. Katz (1979) employed some as-pects of crane social behavior to quantify seasonalchanges in mated pairs of hooded cranes. Nesbittand Archibald (1981) described some agonisticdisplays for sandhill cranes. Partial sociogramsare available for the following species: whoopingcrane (Allen, 1952; Kepler, 1976), Siberian crane(Poulsen, 1975; Sauey, 1976), Eurasian crane(Poulsen, 1975), and sandhill crane (Voss,1976a,b; Tacha, 1981).* Corresponding author. E-mail: david–h–[email protected]

0376-6357/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved.

PII S0376-6357(98)00008-4

D.H. Ellis et al. / Beha6ioural Processes 43 (1998) 125–151126

Table 1Current nomenclature of the world’s cranes

Scientific nameCommon name Species groupAbbreviation in Table 2

Black crowned crane Balearica pa6oninaB Cr Crowned crane groupBalearica regulorumG Cr Crowned crane groupGray crowned craneBugeranus carunculatusWattled crane Long-train groupWattAnthropoides paradiseaBlue Long-train groupBlue crane

Demoiselle crane Anthropoides 6irgoDem Long-train groupGrus leucogeranusSibe Siberian craneSiberian craneGrus canadensisSandhill crane Sandhill craneSandGrus 6ipioWh-N Bare-faced groupWhite-naped craneGrus antigoneSarus crane Bare-faced groupSarGrus rubicundaBrol Bare-faced groupBrolgaGrus grusEurasian crane Eugrus groupEuraGrus monachaHood Eugrus groupHooded crane

B-NkBlack-necked crane Grus nigricollis Eugrus groupGrus japonensisRed Eugrus groupRed-crowned crane

WhooWhooping crane Grus americana Eugrus group

A partial ethogram, including only the non-so-cial behavior for the world’s cranes, has beenpublished (Ellis et al., 1991). This is the socialethogram: it consists of two parts. First is thesociogram (sensu Wilson, 1975), a description ofall social displays, together with higher level be-havior sequences, here termed activities (e.g.Dance or Attack). The second part is a tabulation(Table 2) of the presence and importance of eachsocial ethon (a non-restrictive term for behavioralacts as simple as a reflex or as complex as anactivity: sensu Ellis, 1979) for each species.

Social signals in many groups of animals aredifficult to recognize and disentangle. Many aresubtle, are graded in their effects and expressions,and have a variety of effects on the recipient (seeWilson, 1975:199). Also, different observers some-times apply different criteria in naming and sepa-rating displays, thereby making comparisonsbetween taxa very difficult (Nelson, 1978). Thelarge number of displays we describe for cranes,in part, reflects the relative ease with which anexperienced observer can distinguish their ratherobvious social signals. Because our primary goalwas to name and characterize homologous dis-plays in all species, we were forced to generalizethe description of some ethons to allow for varia-tion between species. The result is that this paperand Ellis et al. (1991) together provide a nearly

complete compendium for the behavioral reper-toire of all species of cranes. However, our de-scriptions are, for many ethons, too general torepresent an ethogram for any species. As such,this paper supplies the structure for future etho-grams for all species.

While we present all ethons that have a socialcontext, our primary focus is on social communi-cation, which is defined as the transfer of informa-tion (Hailman, 1977) often resulting in the overtalteration of behavior of the recipient. We recog-nize that some crane displays (e.g. Pre-Attack)function interspecifically (Viess, 1981).

The reader should be aware that, while we haveattempted to report likely sign vehicles, effectivestimuli, or releasers (i.e. those aspects of eachsignal that influence the response of the communi-cant), it was beyond the scope of this paper toperform the necessary experiments to do so thor-oughly. In many agonistic encounters, brightly-colored bare skin is prominently featured, butwhether this is the actual sign vehicle that releasesor retards aggression, or whether it acts in concertwith body position and motion or other featuresof the display are unknown. The elucidation ofsuch releasers in cranes must await additionalresearch.

The family Gruidae (Table 1) is an ancientgroup whose earliest known fossils are from

D.H. Ellis et al. / Beha6ioural Processes 43 (1998) 125–151 127

Eocene deposits ca 50000000 years old (Olsen,1985). Cranes have body parts conspicuouslymolded for use as visual and auditory signals overlong distances, and since they move slowly, rela-tive to many other animals, the forms of theirdisplays can be readily perceived and analyzed.Even so, many subtle signals (such as iris dilation)have only recently come to light, and others mayas yet remain undiscovered.

Archibald (1976a) had previously used only asingle social display, the Unison-call, to distin-guish species groups. The phylogeny resultingfrom this approach has been largely confirmed byrecent molecular genetics studies (Dessauer et al.,1992; Krajewski and Fetzner, 1994). Our ap-proach was to look less intently at any one dis-play, but to evaluate the whole spectrum of socialdisplays toward identifying species groups on thebasis of presence or absence of displays. Ourstudy benefitted from ample time (ca 30 years)and a pooling of observations from numerousstudents of crane behavior.

2. Methods

All 15 species of cranes have been held incaptivity at one or both of our institutions (Patux-ent Wildlife Research Center, two species (includ-ing four subspecies), 31 years; and InternationalCrane Foundation, 15 species, 28 years). The useof captive animals has long been recognized as anessential component of behavioral research(Lorenz, 1935). Indeed, a continuum of researchopportunities exists between the field and the lab(Lehner, 1979), and both are needed to allowresearchers to observe the minute details (fromcaptive animals) and proper context (from freeranging animals) of animal social behavior (Men-zel, 1969). Most of our observations were madeon captive birds held in relatively large outdoorenclosures (many netted; with the result that occu-pants of these were capable of flights up to 30 m)designed to allow a full expression of social dis-plays. Because some individual animals developabnormal behavior in captivity (Tinbergen, 1962),all of our descriptions are based on observationsof more than one individual, and, whenever possi-

ble, have been augmented by work on wild cranes.Where certain behavioral anomalies (such as fencepacing or the development of homosexual pairs)have appeared, pen or other modifications weremade to eliminate them (Kepler, 1976, 1978;Viess, 1981). We feel confident that the socialdisplays described herein are typical of wild birds,although we recognize that their frequency ofperformance has been greatly altered by captivity.

We have greatly benefitted from the specialopportunities derived from living in close proxim-ity to breeding pairs of all species, and especiallyfrom working with hand-reared birds. Most hand-reared birds respond toward approaching humansas for intruding conspecifics or, in some instances,as for an approaching mate. This situation en-abled us to vary the stimulus situation (i.e. ourpresence) to thereby determine the hierarchy ofsocial displays. At the approach of a human, tameor imprinted birds first show alert behavior, thenlow-intensity threat displays, then, if the humancontinues to approach, they display more intently,and may finally attack by lunging, stabbing, etc.The result is that a decade of field observations,especially for the less social species, may not yieldthe number of observations of some of the moreintense social displays that can come from a singlestroll through our captive colonies. We also notethat many of the subtle features of crane socialbehavior (e.g. Iris-expansion, Feather-tuft-erec-tion) have gone undetected or unreported untilthis study because they are inconspicuous exceptwhen viewed from very near.

In the compendium that follows, we deal withthe form and context of social (auditory andvisual) displays in cranes. In describing each so-cial ethon, we included orientation of body parts,sounds, movements, feather positions, and evensubtle cues such as iris expansion or the degree ofbare skin coloration and expansion. We also men-tion probable sign-vehicles (e.g. color or pattern)that characterize the displays (Hailman, 1977).

We recognize that, in describing the behavior ofa species, it is often difficult to separate ethons atthe appropriate level. More specifically, it is im-portant to recognize that some behavioral acts aremerely components of more complex displays.For example, we noted that two species of cranes


Tab

le2

Soci

albe

havi

orof

the

wor

ld’s

cran

esa

Eth

onSi

beB

Cr

Sand

Wh-

NSa

rB

rol

Eur

aH

ood

B-N

kR

edW

hoo

GC

rW

att

Blu

eD

em

I.V

ocal

izat

ions

++

++

++

A.

Pee

p+

++

++

++

++

++

++

++

++

++

++

B.

Foo

d-be

ggin

g+

++

++

++

++

++

++

++

++

+C

.N

esti

ng-c

all

++

++

++

D.

Con

tact

-cal

l+

++

++

++

++

++

++

++

++

++

++

+E

.P

re-fl

ight

-cal

lP

P+

P+

++

++

++

++

+P

PP

F.

Flig

ht-c

all

++

++

++

+G

.A

larm

-cal

l+

++

++

++

++

++

++

++

++

++

+H

.G

uard

-cal

l+

++

++

++

++

++

++

++

++

+I.

Uni

son-

call

P+

++

++

++

++

++

++

++

++

PP

J.L

ocat

ion-

call

++

++

++

++

++

++

+K

.St

ress

-cal

l+

++

++

++

++

++

++

++

++

+L

.D

istr

ess-

call

++

++

++

+M

.M

oan

+P

++

P?

??

++

++

++

++

++

++

N.

His

s+

++

++

++

++

++

++

++

++

+O

.P

re-c

opul

ator

y-ca

llP

.C

opul

ator

y-ca

ll−

−−

−−

−+

++

++

−−

−−

−P

−−

−−

−−

−−

+−

−−

−Q

.T

hora

cic-

clic

kII

.A

goni

stic

disp

lays

++

++

++

++

++

++

++

A.

Ale

rt+

−−

++

−−

−−

−−

−−

−−

++

B.

Iris

-exp

ansi

on−

++

++

++

+−

+C

.B

are-

skin

-exp

ansi

on+

+−

++

++

++

++

+D

.B

are-

skin

-pre

sent

++

++

++

++

++

++

+−

−+

++

−sl

++

++

++

++

++

++

+E

.F

eath

er-t

uft-

erec

tion

++

++

−+

−−

sl+

+−

−−

−−

+−

−F

.G

ular

-exp

ansi

on+

++

++

++

++

+G

.T

erti

al-e

leva

tion

+−

++

+−

−−

−+

++

++

++

+sl

sl?

sl+

+sl

H.

Hea

d-ru

b?

?+

++

++

++

++

++

++

++

++

++

++

I.P

re-s

trut

+vH

++

vH+

Vh

+v

+v

++

VH

++

VH

J.St

rutb

++

H+

v+

+V

h+

+V

h+

v+

v+

v+

vsl

−+

−−

−−

+−

++

−−

++

K.

Hea

d-fli

ck+

++

++

++

D+

slD

+sl

D+

slD

+sl

D+

+D

++

D+

+D

++

D+

DR

++

+L

.D

orsa

l-pr

eenc

++

++

++

+M

.V

entr

al-p

reen

+−

++

−+

++

++

++

++

+P

+P

+P

N.

Win

g-fli

ck-fl

ight

+P

P+

++

++

++

P+

++

++

++

++

+P

PO

.B

ill-d

own-

hold

P−

++

++

P+

++

P+

+−

PP

P.

Bill

-dow

n-gr

owl

++

−−

+?

+?

P?

+−

−Q

.B

ill-d

own-

swee

p−

−+

+−

++

+?

+?

??

?+

?−

−+

R.

Blo

w-b

ubbl

es+

++

++

++

S.St

ab-n

ibbl

e-tu

g+

++

++

++

+−

−−

−−

−−

+−

+−

−T

.H

ead-

low

er-r

uffle

++

++

+−

−+

++

++

++

++

++

++

++

+−

−−

U.

Ruf

fle-b

ow?

+−

−−

−−

−−

−−

−+

+sl

V.

Win

g-sp

read

-hol

d+

−+

++

++

+−

++

+−

++

W.

Win

g-sp

read

-flap

++

++

−−

−−

−−

−−

−−

++

++

+X

.T

ail-

wag

++

++

++

++

++

++

++

+Y

.St

omp

P+

P+

+P

+P

+Z

.L

eg-q

uive

r+

++

+P

P

D.H. Ellis et al. / Beha6ioural Processes 43 (1998) 125–151 129T

able

2(C

onti

nued

)

Sibe

Eth

onSa

ndB

Cr

Wh-

NSa

rB

rol

Eur

aH

ood

B-N

kR

edW

hoo

GC

rW

att

Blu

eD

em

−−

++

sl+

−−

AA

.C

atap

ult

−−

−−

−−

−−

−−

−−

−+

++

−+

+−

−+

+B

B.

But

terfl

y−

−−

−−

−−

−−

−−

−−

++

+−

−−

−C

C.

Arc

h+

++

++

++

++

DD

.H

oove

ror

Nec

k-cr

ane

++

++

−−

−+

++

++

++

++

++

++

++

++

++

++

++

EE

.C

rouc

hF

F.

Pre

-att

ack

++

++

++

++

++

++

++

+II

I.A

ttac

kan

dm

ob+

++

++

+A

.R

un-fl

ap+

++

++

++

++

++

++

++

++

++

++

B.

His

s+

++

++

++

++

++

++

++

++

+C

.G

ape

D.

Bill

-sta

b+

++

++

++

++

++

++

++

++

++

++

++

++

++

E.

Jum

p-ra

ke+

++

F.

Win

g-th

rash

++

++

++

++

++

++

++

+IV

.D

efen

si6e

and

subm

issi6e

disp

lays

and

acti6i

ties

++

++

++

A.

Win

g-fla

re-c

ower

++

++

++

++

++

++

++

++

++

++

+B

.C

ower

++

++

++

++

++

++

++

++

++

C.

Cow

er-c

rouc

h+

++

++

++

++

++

++

++

D.

Dis

trac

tion

-dis

play

?+

??

P+

?+

??

??

PE

.B

unch

ing

PP

++

++

++

++

++

++

++

+F

.F

lee

G.

Pre

-cop

ulat

ion

+P

++

++

++

++

++

++

+V

.C

onco

rdan

tbe

ha6i

or+

++

++

++

++

++

++

+A

.C

onta

ct-c

all

++

++

++

++

++

++

++

+B

.P

re-fl

ight

++

++

++

++

++

++

+C

.P

re-fl

ight

-cal

lP

P+

P+

++

++

++

++

+P

PP

D.

Flig

ht-c

all

++

++

++

++

E.

Flig

ht+

++

++

++

??

??

??

??

??

+?

+?

F.

Allo

pree

n?

VI.

Pai

rre

late

dbe

ha6i

or+

++

++

++

++

++

++

+A

.U

niso

n-w

alki

ng+

++

++

++

++

++

++

++

B.

Uni

son-

call

++

++

++

++

++

++

++

C.

Dan

ce+

++

++

++

++

++

++

++

++

1.Sp

read

-hol

d+

++

++

++

PP

PP

P+

++

2.G

ape

++

++

++

++

+3.

Gap

e-sw

eep

++

++

++

++

++

++

+4.

Tuc

k-bo

b+

++

++

++

++

++

++

++

++

P+

+5.

Lea

p+

+P

++

++

++

++

++

++

++

+6.

Obj

ect-

toss

++

++

++

+7.

Run

-flap

-glid

e+

−+

+−

++

++

++

++

++

?+

++

+8.

Hoo

ver

orN

eck-

cran

e−

−+

sl−

++

++

++

++

++

++

−+

sl9.

Bill

-sta

bD

.P

re-c

opul

atio

n+

++

++

++

++

++

++

++

++

++

++

++

++

++

++

+E

.C

opul

atio

n-ca

llF

.C

opul

atio

n+

++

++

++

++

++

++

++

VII

.N

est

prep

arat

ion

and

mai

nten

ance

beha6i

or+

++

++

++

++

++

++

+A

.Si

dew

ays-

toss

++

++

++

++

++

B.

Swee

p-dr

op+

++

++

+


Tab

le2

(Con

tinu

ed)

Sibe

Sand

Wh-

NSa

rB

rol

Eur

aH

ood

B-N

kR

edE

thon

Who

oB

Cr

GC

rW

att

Blu

eD

em

+?

P+

+P

PP

PP

++

PP

C.

Nes

t-pr

obe

P P+

P+

++

+P

PP

P+

P+

PP

D.

Tre

adV

III.

Par

enta

lbe

ha6i

or+

++

++

++

++

++

++

++

A.

Ovi

posi

tion

++

++

++

++

++

++

++

+B

.H

igh-

step

+ ++

++

++

++

++

++

+C

.W

addl

e+

++

++

++

++

++

++

++

D.

Shuf

fle+

++

++

++

++

++

++

++

++

E.

Sett

le+

++

++

++

F.

Bill

-tuc

k+

++

++

++

++

++

++

++

++

++

+G

.In

cuba

tion

++

++

++

++

++

++

++

++

++

H.

Bro

odin

g+

++

I.Sh

adin

g+

++

++

++

++

++

++

+P

++

+P

PP

PP

P+

PJ.

Tre

adP

+P

++

++

++

+K

.N

esti

ng-c

all

++

++

++

++

++

++

++

++

+L

.P

rese

nt-m

orse

l+

++

++

+M

.D

istr

acti

on-d

ispl

ay+

++

++

++

++

++

++

++

IX.

Fili

albe

ha6i

or+

++

++

++

++

++

++

++

A.

Pee

p+

++

++

++

++

++

++

+B

.C

onta

ct-c

all

+ ++

++

++

++

++

++

C.

Foo

d-be

ggin

g+

++

++

++

++

++

++

++

+D

.W

ing-

quiv

er+

++

++

++

++

++

++

++

++

E.

Acc

ept-

mor

sel

++

+F

.St

ress

-cal

l+

++

++

++

++

++

++

++

++

++

++

++

+G

.D

istr

ess-

call

++

+

aK

eyto

cell

code

s:?,

Itis

unkn

own

ifth

issp

ecie

spe

rfor

ms

this

etho

nan

dkn

owle

dge

insu

ffici

ent

toco

njec

ture

;+

,th

issp

ecie

spe

rfor

ms

this

etho

n;−

,th

issp

ecie

sdo

esno

tpe

rfor

mth

iset

hon;

++

,th

issp

ecie

spe

rfor

ms

this

etho

nto

agr

eat

degr

ee;+

++

,th

issp

ecie

spe

rfor

ms

this

etho

nto

agr

eate

rde

gree

than

othe

rsp

ecie

s;P

,th

issp

ecie

spr

obab

lype

rfor

ms

this

etho

n;sl

,sl

ight

ly,

spec

ies

perf

orm

san

etho

nth

atsu

gges

tsth

iset

hon.

bSt

rut

vari

atio

ns:

V=

vert

ical

Stru

tis

norm

alfo

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conspicuously flare the feathers of the thigh whenStrutting. Because Thigh-feather-flare was nevernoted outside the context of some more complexdisplay, we do not include it here as a separatedisplay. More difficult to decide if appropriate toseparate were Iris-expansion and Feather-tuft-erection. Although both appear as separate dis-plays, we are nonetheless somewhat uneasy inpresenting them separately because each is also acomponent of more complex displays. When seenalone, they may merely be the precursors of, orevidence of, an inclination to perform a morecomplex display.

We have somewhat arbitrarily divided the so-cial repertoire into nine general categories (Sec-tion 3.1–Section 3.9). The first to be presented isthe vocal (or auditory) repertoire (Section 3.1),which is also presented again by weaving the callsinto the functional classes of the visual displays(Section 3.2–Section 3.9). Unfortunately, there isoverlap between categories even for visual dis-plays because some ethons appear in several con-texts. For example, elements of Attack (Section3.3) appear also in the Dance (Section 3.6C) andare discussed in both contexts. Similarly, theGrowl that is part of the Bill-down-growl threatdisplay seems identical to the Nesting-call of aparent crane calling to its hatching chick, so it istreated in both places.

While our emphasis in this paper is on ethontitles and general descriptions, we provide someinformation on behavioral sequences (e.g. the or-der of appearance of ethons within a typicalDance bout). Our nomenclature generally em-ploys the use of dashes to link descriptive words(e.g. Jump-rake). Because a one word title issometimes sufficient (e.g. Alert), we capitalize thefirst letter in each ethon title to alert the readerthat we are writing restrictively about, for exam-ple, the Alert social display. When speaking non-restrictively about, for example, an attack by apredator, the word ‘attack’ is not capitalizedwhereas when a crane employs elements of At-tack, the word is capitalized. When referring tonon-social ethons described by Ellis et al. (1991),we also capitalize the first word in each ethontitle.

Although we attempted to apply descriptivetitles to all visual displays, most vocalizations arenot easily described (an exception is the Thoracic-click), so each is titled by context (e.g. Pre-flight-call). To save space, we used acronyms in theparagraph where a particular ethon is described,but for clarity, only there. For example, in itsdescriptive paragraph, Gular-expansion is referredto as G-e, but elsewhere, all references to Gular-expansion are spelled out.

The primary method of accumulating data forthis report was to make careful observations andstill photographs while rearing and caring forcaptive cranes. Immediately after observing rarelyperformed ethons, we also took detailed notes ofthe form and context. Super-8 movie films wereexposed and notes were taken on behavioral se-quences. The films were viewed and tracings weremade of selected frames. These tracings and stillphotographs were then abstracted into the illus-trations that accompany the text. After years offamiliarizing ourselves with crane social behavior,in 1988 we joined forces to identify and nameeach ethon and to prepare behavior categories.We subsequently observed even more carefully inan attempt to identify new ethons and new perfor-mance contexts. During the subsequent ten years,we also attempted to verify each cell in the spe-cies-ethon contingency table (Table 2). For exam-ple, Iris-expansion, a very subtle feature firstnoted in the Siberian crane, was found in otherspecies only after careful scrutiny of many captivepairs.

3. The sociogram

Social ethons are presented below in text out-line form that matches the compressed outline inTable 2. The table also provides data on whichspecies perform each ethon and to what degree.For some cells within the table, further study willconfirm or dispute our assessment of the impor-tance of that ethon for a particular species. Theorder of presentation is roughly by age (young toold), by volume (quiet to loud), and by order ofappearance in behavioral sequences (early to late).


3.1. Vocalizations

In ethology, titles for ethons are typically ‘de-scriptive’, but for vocalizations, ‘functional’ titles(providing primary context) are often more useful(Grier, 1984). Much intergradation exists betweencalls with the result that the range of vocalizationsappears as a continuum with identifiable peaks,each of which is given a title. Because variousspecies perform the calls very differently, somecalls classed together here (by context of perfor-mance) may not be true homologs (similar inorigin).

Below, we arbitrarily present vocalizations sep-arate from the other social ethon classes. How-ever, we recognize that calls are most often givenas components of complex social displays. Wherea call is the major or only component of a socialdisplay, the call is presented a second time in theappropriate place in the outline in Table 2. Thescope of this work precludes presenting sono-grams for each call for each species. Nevertheless,we recognize that in ethograms for each speciessonographic analysis will be required.

A. Peep (Voss, 1977; pip call). A quiet, briefwhistle grading into an even briefer chirp or ex-tended into a purr. Beginning 2-3 days beforehatching and grading into the Contact-call whichcontinues throughout life.

B. Food-begging (Archibald, 1976a; Food-beg-ging-call). A rapid series of brief chirps in thechick grading into a single, hoarse, prolongedchirp in fledglings. At least for tiny chicks, thiscall intergrades with the Peep and Contact-call.

C. Nesting-call (Archibald, 1976a; N-c). A quietpurr or growl given at a rate of about one to twocalls/s) is normally given in long series. Quieterand less rigidly cadent than the Copulatory-call.This call is given by adults while nest building,while inspecting nest contents (eggs, chicks, oreven an empty nest), and while Brooding or Feed-ing chicks. During a complete performance, thebill is pointed downward and the bill tip is heldvery near the chick or substrate. In the whoopingcrane, an identical call is performed during theBill-down-growl social display. For the Siberiancrane, the Nesting-call sounds closer to the Stress-call. For some species (i.e. red-crowned, hooded,

Eurasian, and sandhill), the female is much moreprone to give this call than the male.

D. Contact-call (Masatomi and Kitagawa,1975; Alert-call; Archibald, 1976a; C-c). Cranesquietly communicate while foraging and duringother maintenance activities using this call, whichmay actually be two or more similar calls thatintergrade with the quieter Peep and louder Pre-flight-call. In adults, this call is a quiet, brief,hoarse gargle usually given at intervals of severalseconds. The exception is the adult Siberian crane,in which the C-c is one continuous horn-like notealso given at intervals of several seconds.

E. Pre-flight-call (Archibald, 1976a; Flight-in-tention-call). A brief hoarse gargle observed in allspecies but the crowned cranes. Like the Contact-call, but louder, honk-like, and usually given inlong series with about one call per second. Veryoften seen in birds preparing to fly.

A second call, performed by red-crowned andhooded cranes, is given in the same context as theP-f-c, but only during the mating season andalmost always by a female. It is also given atintervals like the P-f-c and sounds like a nasal orhoarse version of the P-f-c, but is believed to bedistinct.

F. Flight-call (Nesbitt and Bradley, 1988 un-publ., F-c). A loud call given at short intervals bycranes aloft. For some or most species (but notthe Eurasian crane), the F-c is like a truncatedGuard-c.

G. Alarm-call (Archibald, 1976a; A-c). This callis evident in all species of cranes. It is a brief,loud, low-frequency blast (higher pitched in theSiberian crane) given alone or in bouts with indi-vidual calls separated by intervals of several sec-onds. Each call is composed of a series of hoarsesubnotes that are given so rapidly that they arenearly inseparable to the human ear. In the sand-hill crane and perhaps all other species, the A-csounds identical to the first call of a Guard-callseries. The common context for all species is thedetection of a distant predator or another threat.

H. Guard-call (Archibald, 1976a; G-c). In thesandhill crane and all other species, pairs andflock mates respond to the approach of intrudingconspecifics and some other disturbances by per-forming loud, guttural squawks (often in series).


In a flock, many birds may be calling at once, butin pairs, the male and female alternate calls intrue antiphonal fashion. It is typically performedin series and somewhat like the Unison-call exceptin the G-c the male and female calls are tempo-rally much alike although the female is higherpitched.

G-cs are often given in series with an interval ofone to several seconds between calls. The sandhillcrane G-c largely replaces (i.e. may be equivalentto) the whooping crane Alarm-call. Crownedcranes give rather loud, honk-like G-cs. For theblack crowned crane, G-c is a simple ‘boom’ whilein the gray crowned crane, it is a disyllabic ‘ka-wonk’. For the Siberian crane, it is a single,unbroken, high-pitched, short call.

I and J. Unison-call (Walkinshaw, 1949; U-c;Armstrong, 1963 (in Masatomi and Kitagawa,1975), antiphonal song). All cranes perform an-tiphonal duets (Archibald, 1976a) which are sexu-ally dimorphic in all species except the crownedcranes. U-cs have been effectively used to deter-mine sex in paired birds (Kepler, 1978) and havebeen employed to determine phylogeny(Archibald, 1976b). Although much variation ex-ists between species, in general, both birds callstanding side by side with necks upright and,when highly aggressive, standing on tip toes toincrease height. For Anthropoides and Bugeranus,each duet lasts 5–7 s, with one male call emittedfor each female call. Demoiselle cranes keep theirwings folded throughout the duet, but the femaleelevates her bill to almost or beyond the vertical,while the male calls with bill slightly above thehorizontal. Blue and wattled males elevate theirhumeri briefly at the end of the duet. Siberiancranes also emit one male call per one female call,but the duet can continue for several minutes.Mates call alternately, the male lower pitchedthan the female, resulting in a duet resembling aEuropean police siren. All other Grus species alsohave duets of indeterminate length; however, foreach male call the female usually emits 2–3shorter and higher calls. For some species andsexes (i.e. sandhill (both sexes), sarus, brolga andwhite-naped (only females)), the wings are closedthroughout the duet. The female always beginsthe duet in sarus, brolga and white-naped cranes,

and the male always elevates his wings and dropsthe primaries (Fig. 1) in turkey-strut (Meleagrisgallopa6o) fashion. The Siberian, whooping, red-crowned, black-necked, Eurasian, and hoodedcranes sometimes walk slowly while duetting andthe wings of both sexes may be elevated withprimaries lowered. During low intensity displays,birds duet without elevating their wings.

Crowned cranes perform a long series of syn-chronized Guards-calls and a gular Boom (graycrowned cranes) or Honk (black crowned cranes)in place of the U-c. The head is held down withthe bill drawn against the neck. As a Boom (orHonk) is given, the bill is swept quickly to theside. Members of a pair give alternate Booms orHonks in series that sometimes last several min-utes. Remarkably, the Boom serves a Guard-callfunction in the black crowned crane and as a U-cin the gray crowned crane.

J. Location-call (Archibald, 1976a; L-c). A veryloud trumpet-like blast. If performed in a bout, atleast several seconds of silence follow each call.When widely separated across a marsh, pair mem-

Fig. 1. Unison-call, white-naped crane (male is at left).


bers L-c in an apparent effort to determine matelocation. To the human ear, the L-c is very like,although more drawn out than, the first note of aUnison-call.

K. Stress-call (Archibald, 1976a; S-c). Theplaintive prolonged nasal chirp of a chick thatgrades into a loud wailing in the adult. Seen incontext of prolonged hunger, thermal stress, orthreat of capture.

L. Distress-call. Probably the full expression ofthe Stress-call, but in the adult whooping crane(and all but the crowned cranes), D-c is a long,multi-note, grating scream given in series duringcapture and handling. Crowned cranes in distressemit a prolonged honk given in extended series.

M. Moan. An energetic moan is emitted bysome cranes during the most intense portion ofthe Ruffle-bow social display (e.g. sandhill,Siberian, sarus, brolga, and white-naped cranes).In the Red-crowned, it is given in transition fromCrouch to Ruffle-bow. The sound is either a nasalbuzzing or, more likely, a syringeal vocalization.It is performed with the bill closed. The Moan isso inconspicuous as to escape detection in thewild. Even in captivity, it can only be heard from,at most, a few meters.

N. Hiss. A loud hissing, emitted with bill closedor agape, is evident during the Pre-attack displayand during an actual Attack. Probably performedby all species.

O and P. Precopulatory-call and Copulatory-call (Archibald, 1976a; P-c). Much like the Nest-ing-call, the P-c begins as a Contact-call, thenbecomes regular and louder growl. For five spe-cies, (i.e. Eurasian, hooded, whooping, black-necked, and red-crowned cranes), the P-c gradesinto a loud scream, the C-c. For all other species,the P-c is also the call given during actualcopulation.

The P-c is performed in long series in which oneto two calls are given per second. Sometimes aseries will continue for 10 min without interrup-tion until Copulation is complete. While givingthe P-c, the bill is directed skyward and the birdadvances in a slow rhythmic gait (very often withits mate in tow) as described for the Precopula-tory-display (Section 3.6, D and E). The P-c is asoft purr in the crowned crane.

Q. Thoracic-click. This noise, evident only inwattled (and perhaps sandhill) cranes, is given fora short period following capture. It appears as aquiet, but conspicuous thump or throb. On firsthearing, it sounds like a loud heart beat, but it isgiven at about one second intervals (i.e. cadencetoo slow for heart beat). From careful inspection,we believe its origin is thoracic rather than buccal,nasal, or syringeal, with the result that it is mostlikely merely a pneumatic sound rather than avocalization with social significance.

3.2. Agonistic displays

Cranes use at least 32 agonistic displays notincluding vocalizations.

A. Alert (Masatomi and Kitagawa, 1975; A).When a crane becomes aware of a distant intrud-ing conspecific, a predator, or some other alarm-ing stimulus, it adopts a characteristic posturewith its head extended maximally up and some-what forward while watching the stimulus. Typi-cally the bird remains still, briefly. All speciesexhibit the A posture, but mated males typicallyelevate the head higher while females extend theneck more forward. The dominant bird (also nor-mally a male) in a group will normally stand taller(i.e. show more A behavior) and have a moreexpanded red cap, face or wattles than subordi-nate birds. Adult males assume a greater role inwatching for threats to the pair or family than dothe females (e.g. Tacha, 1988:16). While A cer-tainly carries a behavioral message to othercranes, it may also merely be the most efficientmeans of surveying the environs.

B. Iris-expansion. Captive male Siberian andwattled cranes clearly exhibit this behavior. It isalso somewhat evident in whooping cranes. Typi-cal context is a defensive male approaching aterritorial violator. In such encounters, the femaletypically remains in the background and shows I-eto a lesser degree if at all.

C. Bare-skin-expansion and Bare-skin-contrac-tion. Except for the two species that lack barepatches or wattles, cranes during display expandtheir unfeathered areas to show dominance oraggressiveness and contract them when ill orsubordinate.


In the whooping crane, both the red papillosecrown and the red-black mustache strip are ex-tended (Fig. 2). Although these areas are con-cealed by feathers in juvenile birds, they arenonetheless expanded during display.

D. Bare-skin-present. When an intruder is faroff, a dominant or territorial bird may Bare-skin-expand or stand Alert, but do nothing else tothreaten. As the intruder approaches, for the spe-cies with red caps, the displaying bird will turn itsbill away from the intruder and thereby maximizethe red surface area presented, all the while usingits peripheral vision to maintain visual contactwith the intruder. Periodically, the displayer inter-rupts its performance of B-s-p to look directly atthe intruder for a second or two, then resumes itsrather odd stance of looking down and away fromthe object of its display. Only those species (13)which have bare skin areas present them.

E. Feather-tuft-erection, Head-fluff, and Head-sleek. The two species that lack specialized bareskin areas compensate by displaying special feath-ered areas on the head or neck. The demoisellecrane erects its white, post orbital plume. Theblue crane flares (H-f) its cobra-like nuchal hood.Context of performance is as for Bare-skin-expan-sion and Bare-skin-present. The converse of H-f(and F-t-e) is H-s.

Most of the cranes that expand bare skin areasalso erect small feather tufts. For some species,the movement of these tufts is inconspicuous evenin captivity. For the black-necked crane, the

Fig. 3. Tertial-elevation and Strut, Eurasian crane.

flaring of feathers of the auricular area is moreconspicuous than for any other species. The phy-logenetically aberrant crowned cranes conspicu-ously flare their crowns in threat contexts, butalso perform a normal variation of the F-t-e.

F. Gular-expansion. Three of the five speciesthat inconspicuously or never exhibit Feather-tuft-erection do perform G-e in contexts like thatfor Feather-tuft-erection and Bare-skin-expan-sion. Most apparent in the closely related sarusand brolga cranes, this display consists merely ofexpanding the pharynx while facing an intruder.

G. Tertial-ele6ation (Masatomi and Kitagawa,1975; Adornment). Not performed by thecrowned cranes or the three long-train species, T-eis evident in all other species (Table 2) and mostpronounced in the Eurasian crane (Fig. 3) forwhich the tertiaries are raised past perpendicularwith the plane of the back. T-e appears as aseparate display and as a component of moreelaborate displays, especially Strut and Unison-call. When so displaying, the crane most oftenturns so its lateral aspect is visible to the intruder.Fig. 2. Bare-skin-expansion, whooping crane.


H. Head-rub. The crown and side of the headare rapidly rubbed on the back or wing. Mostoften performed in company with ritualizedpreening, this display appears as a displacementactivity in moderately intense agonistic encoun-ters. Commonly seen in three species (Table 2),H-r is also occasionally performed by at least nineother species including both crowned cranes. H-ris performed more often by females. By context,H-r seems to indicate some ambivalence betweenapproaching and avoiding an intruder.

I. Pre-strut (Masatomi and Kitagawa, 1975;adornment). This static display is seen in allfifteen species. It is a modification of Alert pos-ture with the added components of Bare-skin-ex-pansion, tertiary-elevation, and elevation of thighfeathers (some species only). It sometimes includesa lifting component wherein the bird stands on itstoes with the foot pad off of the substrate. As forAlert, this display is primarily performed by terri-torial males. P-s is at approximately the samelevel of intensity as, and is often followed by,Guard-calling or Unison-calling.

J. Strut (Masatomi and Kitagawa, 1975; adorn-ment-walk). Performed by all species, this display(Fig. 3) is a specialized walk wherein the craneturns sideways to present its lateral aspect to therecipient and walks in slow, measured steps. Be-tween steps, each foot is lifted high and toe exten-sion is exaggerated. Bare-skin-present isconspicuous in the sandhill crane, and tertiaryelevation is especially evident in the Eurasiancrane. Two general forms are evident: either theaxis of the body is nearly horizontal or muchmore vertical (Fig. 3). Table 2 indicates whichform is most often seen in each species. Othercomponents evident in extreme performances in-clude a lateral flaring of the thigh and tibio-tarsifeathers (especially in whooping and black-neckedcranes) and occasionally dropping of the pri-maries (whooping crane).

K. Head-flick (Masatomi and Kitagawa, 1975;irrelevant-head-shake). Five or six species (Table2) show a quick, but conspicuous, sideward toss-ing of the bill in display context. In the bluecrane, a bill-clacking or bill-rattle component isalso present. In the related wattled crane, a rat-tling sound is also made, but by the wattles

Fig. 4. Dorsal-preen, whooping crane.

slapping against the head rather than by a click-ing of the bill. In these two species, it is frequentlyperformed as part of Head-lower-ruffle, discussedlater.

L. Dorsal-preen (Masatomi and Kitagawa,1975; Irrelevant-back-preen; Voss, 1977; PreenDisplay). Ritualized preening is probably themost frequently performed non-static, social dis-play. The back, tertiaries, or scapulars are theprimary sites of bill contact (Fig. 4). Several com-ponents of the display suggest that other thannormal preening is involved: first, the D-p isconsistently performed at the same, rather smalllocation; second, the preening components areabbreviated and interrupted (sometimes resultingin the bird merely contacting the spot with its billfor several seconds without nibbling the feathers);third, after a few seconds with the bill on back,the bird very often lifts its head to observe therecipient, then returns to preen or point at thesame spot; fourth, a consistent wing-drop compo-nent (Fig. 4) often accompanies D-p especially inthe Siberian crane, but also in nine other species;and finally, D-p is also very often part of adisplay sequence beginning with Alert, then Pre-strut. An interesting D-p component especiallyevident in the Siberian crane is Iris-expansionmaximizing display of the yellow iris.


formed by the remaining two species (Table 2).Performance of B-d-h consists of lowering thehead until the bill touches or nearly touches theground and holding this posture. For the crownedcranes, B-d-h is the complete display. All otherspecies probably (five species) or surely (eightspecies) add a growl component that sounds likethe Nesting-call. Sometimes a Siberian crane willB-d-g while turning slowly, occasionally making acomplete circle. Usually one mate performs thesedisplays at the approach of an intruder. Thesedisplays are especially pronounced in the Siberiancrane, a species which also adds a component(B-d-s) in which the neck sways side-to-side caus-ing the bill to sweep left and right in an arc ca 50cm in length.

We propose three possible origins of these dis-plays. First, the Bill-down component, from adistance, looks like a standing adult attending achick. Next, the growl is similar to or equivalentto the Nesting-call, and in some performances, theadult nibbles at twigs in a manner suggesting nestbuilding especially when coupled with the sweepcomponent of the Siberian crane. These displaysappear then to be ritualized chick care and/orritualized nest building. Either could convey tothe recipient that the displaying crane has a deepcommitment to the site and probably could beexpelled only with difficulty. Alternately, this be-havior may be ritualized foraging as suggested byVoss (1977).

R. Blow-bubbles. In the Siberian crane and afew other species (Table 2), a threatened cranemay perform what appears to be Bill-down-growlwhile standing in water. For Siberian cranes, thebill is flicked side-to-side, as if stirring the water,with the result that the display appears to beritualized feeding. Alternately, B-b is merely anaquatic performance of Bill-down-growl or Bill-down-sweep.

S. Stab-nibble-tug (Masatomi and Kitagawa,1975; irrelevant-ground-stick; Voss, 1977; Forag-ing Display). This display, common to all species,is often closely linked with Bill-down-hold, Bill-down-growl, Bill-down-sweep and Crouch (Sec-tion 3.2, EE). During most performances, a crane,while being approached by an intruder, nervouslyStabs at the ground and/or Nibbles and/or Tugs

M. Ventral-preen (Masatomi and Kitagawa,1975; Irrelevant-leg-preen). As for Dorsal-preen,all species but the crowned cranes perform this.Normally in V-p, the crane preens and/or contactsa small area at the junction of the belly, thigh,and proximal tibio-tarsus. A peculiar neck exten-sion component identifies this as a display. V-p isvery often the final component of the Hoover andRuffle-bow displays discussed later.

N. Wing-flick-flight. This display gradessmoothly into normal flapping flight and can bedifferentiated only when extreme. When display-ing, the wing stroke is shallower, the glide be-tween strokes longer, and the upward flick for thenext stroke is more rapid. Although it has beenobserved in ten species, all species of cranes prob-ably use this display. Cranes W-f-f when pa-trolling territorial boundaries, when pursuingintruders, and during courtship.

O, P and Q. Bill-down-hold, Bill-down-growland Bill-down-sweep (Voss, 1977; Foraging Dis-play). At least two of these displays have notpreviously been described. However, Poulsen(1975) may have entitled one of them Bill-to-ground. Some form of these displays (Fig. 5) issurely performed by 13 species and probably per-

Fig. 5. Bill-down-growl, whooping crane.


at vegetation (at least three separate foragingaction patterns (Ellis et al., 1991) are involved).Some performances suggest ritualized nest build-ing, but most performances appear as true dis-placement activities that have not been ritualized.Although this is an aggressive display, the contextshows a strong fear component as well.

T. Head-lower-ruffle. This display is found onlyin two crane groups, the crowned cranes plus theLong-train Group (the three species in Table 1that have long trailing tertials). It is a homolog ofthe Ruffle-bow discussed next. In a typical perfor-mance, the head is dipped forward and rapidlyshaken. Most often performed while walking.

U. Ruffle-bow (Masatomi and Kitagawa, 1975;wing-shake-bow; Voss, 1977; Body-wing-shakeDisplay). As stated above, R-b replaces the Head-lower-ruffle of five species. R-b (Figs. 6 and 7) isperformed by the bird presenting one side towardthe intruder/recipient, then commencing what ap-pears to be a maintenance Ruffle-shake (Ellis etal., 1991). First, the feathers are elevated, then thebody begins gyrating side-to-side as the wings liftslightly then slap closed, in left and right cycles ofincreasing crescendo and vigor until the body ofthe bird whirs back and forth in a flurry ofshaking. Two versions of Ruffle-bow are known.

Fig. 7. Ruffle-bow-up, whooping crane.

For the species that show R-b-down (Fig. 6, e.g.sandhill crane and four other species), when thegyrations reach a peak, the head is thrown for-ward and down with the bill pointed rearward,the bird rises onto its toes and a quiet Moan, ca 2s in duration, is emitted. Gyration then ceases andmost often (for the sandhill crane), the bill con-tacts the feathers of the leg and the crane Ventral-preens. For R-b-up (Fig. 7), the head is extendedup and forward and the bill is tucked neck-wardand held for a second or two as shaking frequencyreaches a zenith.

The Moan component, known for ten species,is nasal in quality and emitted with the bill closed.

V. Wing-spread-hold. The wings are lifted highand wide and held spread for :1–5 s. Only thetwo crowned and the wattled cranes perform thisdisplay. It appears as a homology to the displaydescribed next. Evidence for the homology is aslight lowering of the head hinting at the sweepcomponent of the next display.

W. Wing-spread-flap. Most of the world’scranes perform some form of this homolog of thecrowned crane’s Wing-spread-hold (Table 2). Thewings are spread wide and high, then are rapidlyFig. 6. Ruffle-down-down, sandhill crane.


swept in a wide arc forward and down, producingan audible whoosh. This is a common display ofthe white-naped and Siberian cranes. For six spe-cies, as the wings flap, the head and neck sweepthrough a wide arc forward so that they lie underthe forward extending wings. In the blue crane,the head and neck feathers flare (Head-fluff) asthe head sweeps forward.

X. Tail-wag. T-w is the quick side to side tailmovements performed in brief bouts of five to tencycles each. This inconspicuous display is foundonly in the three species with the longest trailingtertiaries (wattled, blue and demoiselle) and thecrowned cranes. A performance is seen in a dis-play sequence with the ritualized preening thatfollows Wing-spread-flap or Stomp (below). T-wis seen as a movement of the tertiaries trailingabove the tail, or the tail may be seen below thetertiaries, elevated for some other display.

Y. Stomp (Masatomi and Kitagawa, 1975;stamp). All species Stomp their feet in an audibleleft-right sequence that lasts :1–2 seconds andincreases in crescendo until it becomes a blur offoot movement. The legs are held nearly straightthroughout so the foot movement is slight. S isalways seen as part of a display sequence. It istypically followed by Leg-quiver discussed next.

Z. Leg-qui6er. This element of some agonisticdisplays is subtle, but readily visible from closerange. We hypothesize its presence in all species,but the movement is slight enough that it must besought to be noticed. The displaying bird standsAlert with its straightened legs moving in a highfrequency, low amplitude shiver. As for the pre-ceding, L-q is an element in a series. A typicalsequence for the whooping crane is Ruffle-bow,Stomp, L-q, Hoover.

AA. Catapult. All elements of this display areperformed only by the white-naped crane, butincomplete performances are also seen in thesarus and brolga cranes. The C is perhaps merelyan elaboration on the Wing-spread-flap display(Section 3.2, W). In both, the wings are spread,held high, then flapped deeply as the head andneck are thrust forward and down. The C em-ploys the added element that the neck is thencatapulted rapidly upward and arched far overthe back, held ca 1 s, then typically loweredforward as the bird commences Ventral-preen.

Fig. 8. Butterfly, whooping crane.

BB. Butterfly. The whooping crane’s equivalentto the Arch, the B (Fig. 8) includes lifting of thethree-quarters open wing high and back and thenstraining or ‘holding the pose’. Unlike the Arch(next), the bill is pointed forward and down. BothArch and B have elements of and appear asprecursors to the Hoover (Section 3.2, DD).

CC. Arch (Masatomi and Kitagawa, 1975;Arch). A (Fig. 9) is probably the red-crownedcrane’s homolog to the Catapult (White-napedGroup, Table 2) and the Butterfly (whoopingcrane). The high-intensity A usually follows sev-eral other, less intense, displays (e.g. Dorsal-preen) and signals near extreme agonistictendency. Performed by arching the neck over theback with the bill pointed :80° above horizon-tal. Simultaneously, the wings are lifted (whileremaining partially folded) maximally above theback. The bird holds the pose one or more sec-onds, then lowers wings and returns bill tohorizontal.

DD. Hoo6er or Neck-crane (Masatomi and Ki-tagawa, 1975; Low-bow and High-bow; Poulsen,1975; bill to ground (but see also Section 3.2, P)).H (Fig. 10) involves two general forms of neckposturing, both are reminiscent of the stem (neck)and handle (head) of a vacuum cleaner, hence the


Fig. 9. Arch, red-crowned crane.

down (extend neck maximally down and slightlyforward, point bill down, and strain). In bothversions, the body axis is high anteriorly. Curi-ously, the sandhill crane and Siberian crane doHoover-down while all of the last five species inTable 2 do Hoover-up except the hooded cranewhich does both. H very often follows alightingand very often involves or follows a wing-spread-up component.

H is closely related to the Butterfly and Arch.In the sarus, brolga, and white-naped cranes, itonly appears following alighting or some otherdisplay and is never performed alone. For thered-crowned crane, H performance, at least some-times, is accompanied by rising onto the toes andby a quiet Moan or Growl. In the red-crownedcrane, the near wing is occasionally lowered andthe far wing spread and lifted during performanceof Hoover. Sometimes both wings are held highwhen red-crowned cranes perform Hoover. Fe-male hooded cranes have an interesting variant inwhich the far wing is lifted during H-down, thenthe bird exhibits a two-wing up-spread while stillin H-down.

EE. Crouch (Masatomi and Kitagawa, 1975;irrelevant-crouch; Voss, 1977; Crouch Display).This, and the next ethon, are the most intenseagonistic displays. They immediately precede out-right Attack if the intruder approaches further.Two versions of C are seen. In both forms, thebird lowers to Lie posture as if Incubating andcompresses the neck feathers. In the Siberian andcrowned crane version, the wings are normally leftcompletely closed, but in all other species, somedegree of spreading is occasionally exhibited.High intensity displays involve more spreading.Having the wings spread also enables a morerapid Attack should the intruder continue to ap-proach. In most species, most of the time, C isaccompanied by much bill contact with nearbyvegetation (Ellis et al. (1991) terms are Stab,Pecking, Nibble, Tug, and Thrash). C in theSiberian crane is unique in that the bird, whenonce crouched, always holds its bill motionless.Crouch appears to be a form of ritualized Incuba-tion and probably signals to an intruder that theperformer has a great investment in the territory(i.e. is nesting).

title Hoover. The two versions are Hoover-up(extend neck maximally upward and slightly for-ward, tuck bill down, and strain) and Hoover-

Fig. 10. Hoover, sandhill crane.


Fig. 11. Pre-attack, sandhill crane.

most or all species, at least in the context of adultsdefending mates or young.

A. Run-flap. If the intruder is at a distance, thecrane may Run while Flapping to enter combat ormay R-f to flee. R-f may be followed by agonisticdisplay rather than combat.

B and C. Hiss and Gape. In an Attack, the birdmay loudly Hiss and Gape widely at the target.

D. Bill-stab (Masatomi and Kitagawa, 1975;upright-peck; Nesbitt and Archibald, 1981; BillSparring). A rapid thrust of the bill (closed orslightly open) is used to injure the target. Preda-tors (e.g. dog (Canis familiaris) and human) havebeen killed by a stab of a crane’s bill (Bent,1926:227).

E. Jump-rake (Masatomi and Kitagawa, 1975;Kick). The crane leaps into the air (Fig. 12) andslashes at its opponent with its talons. Thestrongly curved inside talon is believed to inflictmost of the damage.

F. Wing-thrash. Some damage can also be infl-icted by slapping the wings against the opponent/intruder, but rapid and repeated W-t probablyserve more to confuse and distract than to injure.

3.4. Defensi6e and submissi6e displays andacti6ities

All cranes are believed to have all of the follow-ing displays. These are most often performed byill birds, chicks, and subordinate adults. They arenormally accompanied by Bare-skin-contraction

FF. Pre-attack (Voss, 1977; Spread-wing Dis-play). As the crane approaches (or backs awayfrom) an intruder in preparation for Attack, itwill typically spread and droop its wings so pri-mary and secondary tips droop or touch thevegetation (Fig. 11). The neck is extended upwardand slightly forward with the head facing theintruder. Alarm-call, Guard-call, and Hiss oftenaccompany a display. Young colts are particularlyprone to display P-a just prior to Attacking an-other chick.

3.3. Attack and mob

A and M are ‘activities’ involving many actionpatterns. An A normally is preceded by, and oftenis interspersed with and followed by, several socialdisplays, but is in itself not a display but rather anattempt to dispel or kill an intruder. All speciesshow all of the following A action patterns. Inaddition, pre-fledged chicks of some, and perhapsall, species use some and probably all of the fooddismemberment ethons (described in Ellis et al.,1991) when attacking siblings.

Mobbing, a group rush at a predator or an-other common enemy, has been known for theEurasian crane since at least the 13th century(Wood and Fyfe, 1969). M may be present in Fig. 12. Jump-rake, Siberian crane.


Fig. 13. Cower, sandhill crane.

C. Cower-crouch and Lie-crouch. C-c can beseparated into two versions because of great con-textual and slight physical differences. C-c is theextreme performance of Cower: it differs only inthat the subordinate or depressed bird (most oftena chick) lowers to Sit or Lie posture while per-forming. When performed by an adult on thenest, it becomes Lie-crouch and lacks the neckFluff component. When approached by a preda-tor, an Incubating adult will L-c with the neckforward outstretched or wrapped around thebody to one side. By performing L-c, the adult isprobably not signaling subordinance as in Cower,but rather is probably trying to avoid detection.Once the intruder is very close or shows that ithas located the adult, the performer will often riseand defend its nest, flee, or try to lure the intruderaway.

D. Distraction-display (Masatomi and Kita-gawa, 1975; Diversionary display). An adult at-tending eggs or young may, if approached by afearsome predator, move diagonally away fromthe nest and thus lure the intruder past the off-spring. Often this behavior (i.e. luring away) isaccompanied by a special display. The D-d in-volves drooping and dragging one or both wingsover the vegetation while walking away from theintruder. The head is also held low and the birdmay vocalize Distress-call. This display is proba-bly homologous to the ‘broken wing display ofshorebirds’.

E. Bunching. Some cranes flee at the approachof an avian predator while others (includinggreater sandhill cranes, G. c. tabida ; RodDrewien, Personal communication) rush into acompact group and point bills skyward in anobvious attempt to deter the predator fromattacking.

F. Flee. Another option for a crane is to Walk,Run or Run-flap while Fleeing from an intruder.

G. Pre-copulation (Masatomi and Kitagawa,1975; Irrelevant-wing-open). Described in Section3.6, G, the female form of P-c (Fig. 14) occasion-ally appears in appeasement context when a sub-ordinate crane of either sex performs this displayat the approach of a more aggressive bird. P-c isnot infrequent in pre-fledged chicks 6 weeks ofage and older.

and/or Head-sleek and Feather-tuft-compression,the converse of dominant displays (Section 3.2,C–F). Bunching and fleeing, while fitting underthis heading, are activities rather than displays.Some pair-related ethons (most notably the Pre-copulatory display (Section 3.6, D)) also appear inappeasement contexts.

A. Wing-flare-cower. Like Pre-attack, the wingsare spread and drooped. Differs in that the headis held low with the neck fluffed and curved downand forward (as in Cower, discussed next). Maygrade into Pre-attack when intruder presses.

B. Cower (Masatomi and Kitagawa, 1975;Neck-retracted-submission). In C (Fig. 13), thebody axis is nearly horizontal, the neck is curveddown with the head held low and retracted, andthe feathers of the head and neck are elevated(Fluffed). Very submissive young and ill cranescommonly show this display. In chicks, this dis-play is normally accompanied by the followingrelated and intergrading calls: Peep, Contact-calland Food-begging-call. Masatomi and Kitagawa(1975) identified a Head-down-submission involv-ing the head lowered near the ground rather thanneck coiled. We consider these as two forms of C.A third form, wherein the bill is drawn near theFluffed, but not retracted, neck, has been seen injuvenile birds observing their parents engaged in aterritorial fray (M.A. Bishop, Personalcommunication).


3.5. Concordant beha6ior

All cranes are to some degree gregarious. Sev-eral displays, vocalizations, and activities promotecoordinated movement, and obviate actual At-tacks within a social unit. Pair related ethons,while of the same genre as those discussed below,are presented separately in Section 3.6.

A. Contact-call (Section 3.1, D). This quietgrowl is given at several second intervals as cranesquietly forage together. It grades in a continuumfrom the whistle-like Peep of the chick to thelouder Pre-flight call and Flight-call of fledgedchicks and adults.

B and C. Pre-flight and Pre-flight-call(Masatomi and Kitagawa, 1975; Intentional pos-ture; Section 3.1, E). In a group situation, when acrane adopts the unique neck-stretched-forward-and-up P-f posture (Fig. 15), it faces into the windand gives P-f-c, a louder version of the Contact-call. If other cranes decide to also depart, theyalign themselves with the first, pose in P-f, andalso call. Soon others and perhaps all in the groupjoin in. Then one and perhaps all Run-flap andlift into Flight. A Neck-fluff version (suggestingfear) is occasionally seen in the whooping crane,sandhill crane, and perhaps others.

D and E. Flight-call and Fly. Crane’s normalmethod of Flight (an activity comprised of several

Fig. 15. Pre-flight, Siberian crane.

action patterns: Soar, Glide, Flap, etc.; Ellis et al.,1991) is by constant flapping (i.e. powered flight).However, on migration they often use thermals assupplementary sources of power (Pennycuik et al.,1979). Cranes also save energy in level, poweredflight by Flying in ‘V’ or ‘chevron’ formation(Walkinshaw, 1973; Pennycuik et al., 1979). Fly-ing in formation is aerodynamically more effi-cient, allowing trailing birds to make use of an‘upwash’ of air that spreads laterally behind andbeyond each bird’s wing tips (Burton, 1990). Un-like most birds that F in formation, cranes at leastsometimes F slightly higher than the bird immedi-ately in front of them. Aerodynamic efficiencymay be thereby compromised to a degree. Evenso, they gain some lift from the preceding birdand also benefit by improved visibility (Burton,1990). Wing-flick-flight was discussed earlier (Sec-tion 3.2, N). Some additional Flight displays areprobably present as suggested by Bent (1926:227),but not yet known well enough to delineate here.

F-c is probably identical to the Pre-flight-call,separate only by context. Given while birds arealoft, it is believed to be given even by a birdFlying alone. In this context, F-c may serve tolocate other birds.

F. Allopreen. Both species of crowned cranesPreen the back and neck regions of family mem-bers and mates. A often appears in conflict situa-tions and, as such, it may serve as a displacementactivity or otherwise limit aggression.Fig. 14. Pre-copulation, black-necked crane (female).


3.6. Pair related beha6ior

Pair formation and maintenance in cranes, justas for other bird groups, involves the full range ofagonistic displays, elements of Attack, and severaldisplays unique to pairing. Further, many non-so-cial ethons are performed in synchrony as matestravel together, forage a short distance apart,Alarm-call, and perform a host of social andmaintenance activities simultaneously and in closeproximity. The ethons below are in order, fromleast to most complex, and from first performed(in new pairs or at the onset of a new breedingseason) to those that culminate. Not discussedbelow is Feather-painting (Ellis et al., 1991), anactivity that may have social significance.

A. Unison-walking. Paired cranes very oftenWalk side-by-side or, more often, the male leadswith the female a few paces behind. This behavioris especially evident when an intruder is present.As the intruder approaches, the male may Strutwith the female in tow performing U-w.

B. Unison-call. Described earlier (Fig. 1; Sec-tion 3.1, I), duetting is important in pair forma-tion and maintenance for all species.

C. Dance. D is an activity sometimes involvingmost agonistic displays (Section 3.2), all elementsof Attack (Section 3.3), and some unique actionpatterns. Elements of D appear in play contextsboth for adults and young. D differs from agonis-tic displays by its much more active and flowingnature. Birds in D very often avoid looking di-rectly at the recipient, especially when it is verynear. In D, it is common to observe incipientperformances and grades of intensity in perform-ing. Variation in ‘behavioral quality’ is therebymore evident than in most or all other activities.At least in captivity, D is much less developed incrowned cranes than in other species.

1. Spread-hold (Masatomi and Kitagawa, 1975;Pre-leap). One bird widely fans and lifts its wingswhile at intervals peering at its dance mate. S-h issometimes performed while Walking or Running.

2 and 3. Gape and Gape-sweep. In G, the bill isheld open, often for several seconds. In G-s, theopen bill is rotated laterally (ca 20–50°) awayfrom the recipient, then returned toward. Matesoften G, G-s, and perform the previous display in

tandem, and all three displays often lead into aDancing bout.

4 and 5. Tuck-bob and Leap (Masatomi andKitagawa, 1975; Stoop). These very active dis-plays are most often seen when a pair dances, butbouts of T-b sometimes erupt in a closely crowdedflock. As nearby birds become excited, they beginGaping and Leaping and rushing about. To per-form these displays, a crane rapidly elevates itshead, sometimes Leaping from the ground, thenjust as swiftly crouches low (Fig. 16) with thebody axis depressed forward, and the neck tightlycoiled. Sometimes a crane holds this coiled posefor a second or two, but more often it shoots upand down in several rapid cycles of tucking, thenbobbing up high. The wings are partly spread inmany, but not all, performances. L may lift acrane a meter or more, and is always accompa-nied by some degree of wing spreading andFlapping.

6. Object-toss (Masatomi and Kitagawa, 1975;Throw). Sometimes a crane will Dance alone forseveral seconds before its mate enters the fray.Even when Dancing solo, dancers very often O-t.To perform O-t, a bird Bill-stabs and then graspsa feather (most often), a grass stem, or some otherlight object and tosses it skyward with a quickupward flip of the bill. The object is thereafterGaped at or Bill-stabbed or Jump-raked (Fig. 12)as it floats down. Running, Flapping and Leapingare components of all well developed Object-tossbouts.

Fig. 16. Tuck-bob, gray crowned crane.


7. Run-flap-glide. In the course of a Dance, onecrane (typically the female) becomes intimidatedby the wild gyrations of its mate and retreats inR-f-g (actually three separate action patterns),then comes rushing back Running and Flappingand sometimes Gliding along, barely touching theground. Both birds then whirl and rush about inskipping steps, half aloft, half Running.

8. Hoo6er or Neck-crane (Masatomi and Kita-gawa, 1975; Low-bow and High-bow; Section 3.2,DD). In the midst of a Dance, but especially atthe onset when only one crane is excited, thenon-performing crane will often H (Fig. 10) orperform some other moderate-intensity agonisticdisplay, as if to ward off advances by the dancer.

9. Bill-stab (Section 3.3, D). During a Dancebout, one or both cranes will often B-s at itspartner. Almost always these Bill-stabs are givenfrom too far away to be genuine attempts toinjure.

D and E. Pre-copulation and Copulation-call(Masatomi and Kitagawa, 1975; Irrelevant-wing-open, Wing-spread, and Bill-raise; Voss, 1976a;P-c). All cranes have a conspicuous P-c display.Details of typical sequences of behavior beforeand after Copulation are supplied by Masatomi(1983a) for six species. A typical performance fora whooping crane male or female is for one adultto walk slowly in short measured steps with billpointed skyward (Fig. 17; neck fully extended upand slightly forward). The bird emits a quietgrowl (C-c) in short (ca 0.5 s), rapid bursts sepa-rated by very brief (ca 0.2 s) quiet intervals. In atypical copulation bout, both birds stroll along,one behind the other, bill-up calling. Eventually(and sometimes very shortly), the female (Fig. 14)spreads her wings very wide laterally, with secon-daries drooped, and allows the male to approachfrom behind. The full performance of P-c for herthen includes this wing-spread-droop componentwhich the male ‘normally’ lacks. The female’s P-cdisplay is sometimes given by a subordinate bird(even a male and sometimes even large colts(Voss, 1976a)) in response to the approach of adominant bird.

F. Copulation (Copulation-call). Like Attackand Dance, C really is an activity involving sev-eral component action patterns. Like Attack, it

Fig. 17. Pre-copulation, Siberian crane (male).

also is not a social display. Rather it is theculmination of many social displays. In the Csequence, the pair approach in Pre-copulatorydisplay, but then the male (or sometimes thefemale; Masatomi and Kitagawa, 1975:835)Walks and Flaps onto the back of his mate. Themounting bird lowers to Sit (i.e. rests tarsi onback of his partner) while still Flapping to bal-ance, then presses his tail left or right around thetail of his mate and cloacal contact is completed.We estimate that cloacal contact lasts for 3 to 10s in successful bouts. Some tail-wagging and mi-nor pelvic thrusting may also be present but isinconspicuous. Most often the male dismounts bysliding forward off the front of the female, butmay step backward (Voss, 1976a). Typical boutsof C are followed by some agonistic display(Masatomi, 1983a,b) including Unison-calling formany species.

For the Eugrus Group (five species), a some-what distinct C-c exists. For these species, the callgiven in Pre-copulation increases in crescendo un-til it becomes a wailing scream, the C-c.


3.7. Nest preparation and maintenance beha6ior

All species are believed to have all of the fol-lowing action patterns in their repertoire. How-ever, demoiselle cranes and blue cranes oftenbuild insignificant nests or no nests at all. Assuch, many individual birds likely never performsome or all of the action patterns listed below.

None of the action patterns discussed below,and in the next section (Section 3.8), are of neces-sity performed in social settings. However, weinclude them here (and excluded them from theethogram of non-social behavior (Ellis et al.,1991) based on the logic that all reproductiveefforts of all species are social in nature.

A. Sideways-toss. Stems/twigs are moved to-ward the nest site and onto the nest platformusing S-t. An individual stem may be sequentiallymoved closer and closer in stages until it is finallydeposited on the mound. Typically, an adult willStand facing away from the nest and S-t manytwigs toward the nest, then move to a new siteand repeat. It may take days before a particularstem actually arrives at the mound by this means.We believe that S-t is the more important ethonfor male nest building, while Sweep-drop (below)is primarily used by the female.

B. Sweep-drop. Similar to Sideways-toss butlacking the fling component and including a dis-tinct drop component, this action pattern is usedmore for actual placement of twigs on the moundand rearranging stems on the nest whileIncubating.

C. Nest-probe. The bill is inserted by sequen-tially being thrust deeper and deeper into the nest.The primary function of this action pattern isprobably to test for water encroachment on thenest. In warm climates, it may function to mea-sure heat of decay as for the Megapodes. It isperformed primarily while Incubating.

D. Tread. Probably all species of cranes tramplethe nest surface to compact vegetation prior toIncubation, and T is probably present in therepertoire even of species that normally nest with-out a nest but observations are not available. Seealso Section 3.8, J.

3.8. Parental beha6ior

Most of the ethons listed below have a directfunctional nature and are not primarily displays,if at all. Only the last three (i.e. Section 3.8, K, Land M) have a conspicuous display role.

A. O6iposition. Egg laying is of necessity stereo-typed by physical limitations in long-leggedcranes. The female typically Sits (i.e. breast up,heels down) in something of a Cower posture(Fig. 18; head down, neck retracted) and quiversslightly (strains as egg moves into and out of hercloaca) at intervals, then expels the egg with abrief dip of the lower abdomen. Sometimes an eggactually drops a few cm before contacting thenest.

B and C. High-step and Waddle. H-s involvesexaggerated foot lifting movements (i.e. the foot islifted higher and held up longer than in normalWalking) and is exhibited when approaching andleaving the eggs, as when commencing or finishingan Incubation bout. When near the eggs, a cranelowers to Sit, Incubate posture, and uses theside-to-side movements of W to move forwardover the eggs. In W the heels rest on the substrateand the feet either lie limply on or dangle abovethe nest.

D and E. Shuffle and Settle. As the adult lowersinto Lie Incubation posture, it first Shuffles itslegs closer and closer to the eggs, then in aseparate action pattern, it Settles over the eggsand beds the eggs in its feathers by rocking side-to-side. In some performances, the wings are also

Fig. 18. Oviposition, sandhill crane.


involved, supporting the weight of the bird as itShuffles and Settles.

F. Bill-tuck. At intervals through each incuba-tion day, the ventral side of the bill is pulledacross the eggs and rotates them. In cranes, B-tmost often results in the small end of the eggbeing lifted over the large rather than the eggrolling about its long axis.

G and H. Incubation and Brooding. Althoughincubation (Lying over eggs) and Brooding (Ly-ing, Sitting, or even Standing over chicks) arephysically and functionally alike, we include bothterms because they are so widely accepted. WhenBrooding in Lie posture, the breast contacts thesubstrate (eggs and/or nest), whereas for Sit thebreast is not supporting, and the weight is borneby the heels, tarsi, and sometimes the droopedwings. Chicks, when being Brooded, move aboutbeneath the breast and wing and sometimes pro-trude from the feathers of the back.

I. Shading. Cranes Shade eggs and/or young inStand, Sit, and Lie postures. The wings may betightly closed or spread to a greater or lesserdegree. When Shading, an adult may turn its backto the sun, but for some S bouts, the sun is notbehind the crane. Cranes are not known toslightly lift or slightly extend their wings at inter-vals while S as seen in some other birds (Ellis,1979), nor are there unique positions that distin-guish it from Incubation/Brooding.

J. Tread. Several species of cranes (Table 2) areknown to T on vegetation to open a brood yardor a foraging area (up to 3 m in diameter) for achick (Pomeroy, 1980). Probably all species per-form this activity sometimes. Walking is the pri-mary component, but the step used is somewhatdifferent. In normal Walking or Running, the footcloses so the toes lie parallel as the foot lifts,passing through the vegetation. When Treading,however, the toes are left spread for use in flatten-ing the vegetation.

K. Nesting-call. Described earlier (Section 3.1,C), this quiet, brief growl of the adult is repeatedin rapid series and is most often heard duringIncubation and while the chicks are small. Itsounds similar to the growl given during Bill-down-growl. Adults use this call when respondingto the chick’s Peeps before hatching and in all

other contexts when an adult attends a chick(even fledged young).

L. Present-morsel (Masatomi and Kitagawa,1975; Feed). Parent cranes hold food items nearor at the tip of the bill while presenting them to achick. The adult lowers its head, extends the billlaterally toward the chick, and growls (Nesting-call). Sometimes adults present a morsel, drop it,then pick it up and present and drop it manytimes in succession.

M. Distraction-display (Masatomi and Kita-gawa, 1975; Diversionary display). D-d was dis-cussed earlier (Section 3.4, D).

3.9. Filial beha6ior

Chicks are strongly interactive with their par-ents, calling, approaching, following, and Peckingthe adult’s bill. Distinct ethons are describedbelow.

A and B. Peep and Contact-call. Describedearlier (Section 3.1, A), P is first heard as soon asthe chick breaks into the air cell (2–3 days priorto hatching), and continues with modificationsuntil the chick is independent. P grades into theC-c of chicks and adults, but P-like calls areemitted by ill or subordinate birds even as adults.

C and D. Food-begging and Wing-qui6er. ToF-b, a chick orients toward an adult, holds itsneck retracted (as in Cower) but with the billpointed up, Peeps, and Pecks lightly at the adult’sbill. A W-q component is often present in F-bcontext and perhaps when soliciting Brooding.

W-q is performed by lifting the wings slightlyaway from the body and simultaneously flutteringthem, shiver-like, at low amplitude and at highfrequency (about two to five strokes/s). In tinychicks, W-q is normally accompanied by vigorousPeeping, less so in older chicks. W-q is rare orabsent in colts older than one month.

E. Accept-morsel. Chicks Peep and Peck at theadult’s bill to remove food items. Young andolder birds use the same Peck to steal food fromanother crane, but normally would not Peep whiledoing so.

F and G. Stress-call and Distress-call. The Peepof a neonate is very like the S-c and D-c. Forlarge colts and adults, these three calls and the


Contact-call intergrade, but they are distinctenough at the extremes, and differ in contextenough, to convey different messages to othercranes and merit separate titles here.

4. Discussion and conclusions

Cranes have a tremendously complex repertoireof stereotyped social behavior. Although compari-sons of the number of displays between taxa isdifficult (Nelson, 1978) because one author maydivide a complex display into several componentswhile another author treats each display as asingle unit, comparisons between taxa are possi-ble. Descriptive ethology is founded on thepremise that discrete behavioral acts can be iden-tified. Even more obvious, the ability of animalsto interact socially implies that discrete socialsignals exist and are decipherable by conspecifics.If they are decipherable by conspecifics, then, withcareful study, the ethologist can also tease apartthe social alphabet of a species.

Moynihan (1970) provided a rough yardstick ofthe complexity of the social repertoire of 27 spe-cies of vertebrates. He reported that the numberof social displays per species within each verte-brate class varied from 10 to 26 for fish, 15 to 28for birds, and 16 to 37 for mammals. The apexwas 37 for rhesus macaques (Macaca mulatta), awell-studied primate. When we revisited the sub-ject in the light of subsequent work with birds, wefound general agreement with Moynihan’s (1970)tally. For example, about 25 displays are de-scribed for the black-necked grebe (Podiceps ni-gricollis ; Prinzinger, 1974), 20–30 are known foreach species of Sulidae (Nelson, 1978), 27 for thegreen heron (Butorides 6irescens ; Meyerriecks,1960), 22 for the golden eagle (Aquila chrysaetos ;Ellis, 1979), and about 20 displays for the mourn-ing dove (Zenaida macroura ; Sayre et al., 1993).Hailman (1977) estimated that 50 displays mightbe an upper limit in non-human animals.

The crane social repertoire (Table 2: 60-plusstereotyped social ethons per species (even whennest-related ethons and complex activities are notincluded)), as described herein, would tentativelyplace cranes at the apex of behavioral complexity,

at least for stereotyped social behavior. However,this does not mean that cranes are more complexsocially than any other animal group. Mammals,most notably primates, have a much wider rangeof social expression because they present signalsover a broader spectrum of display intensity. Theyalso use more subtle calls and more variety infacial expressions than we have found in cranes.Wilson (1975:185) referred to graded signals orsignal enrichment to express these concepts. Fur-ther, the nearly infinite number of social expres-sions possible through the use of language placesman apart from all other vertebrates. However,when considering only the number of stereotypedsocial displays, cranes surface as presenting themost complex repertoire known. We are awarethat our level of detail in teasing apart separateethons is greater than that employed in somestudies (e.g. Sayre et al., 1993). However, we haveresisted the temptation when ‘dissecting’ displaysto count components as separate displays.

Fortunately for our efforts to identify discretebehavioral units, most crane displays are bothconsistent and conspicuous. This stereotypy andthe extraordinary complexity of their social reper-toire stems, we believe, from three factors: first,cranes are solitary on the breeding grounds, sec-ond, most are gregarious when not breeding, andthird, all have lethal bills. These traits result infirst, a need to advertise their breeding territoryover long distances (where only conspicuous andstereotyped displays will serve), second, a need tointeract socially over short distances when in aflock, and third, a need to avoid combat leastsevere injury or death result. Nelson (1978), inspeculating about the complexity of sulid socialrepertoire, added two more possible factors,namely large body size and great longevity. It willbe most interesting to see if future studies canidentify unrelated vertebrate taxa that exhibit sim-ilar traits (i.e. species that show seasonal territori-ality, lethal capabilities, etc.) and determine ifthese taxa have developed social signals of com-parable complexity. However, we expect that inthe final analysis cranes will retain what nowappears to be their position as premier amongbirds and perhaps among all other animals in thenumber of salient social displays.


Recently, molecular studies have been used toclarify phylogenies (Ingold et al., 1989; Krajewski,1989, 1990; Dessauer et al., 1992; Krajewski andFetzner, 1994). All of these clearly separatecrowned cranes into a separate subfamily. TheEugrus Group also seems discrete from the re-maining species (Love, 1990; Dessauer et al.,1992; Love and Deininger, 1991). One remainingpoint of controversy is in the placement of thewattled crane (Krajewski, 1989; Krajewski andFetzner, 1994). The molecular genetics studiesagree that the blue crane is probably the wattledcrane’s nearest relative. Our behavioral treatmentagrees that the wattled crane is closely related tothe blue and demoiselle cranes. The frequency,and especially the precise motions, of four wattledcrane displays (i.e. the Head-lower-ruffle, Wing-spread-flap, Tail-wag, and Head-flick) are strik-ingly like those of the blue crane. A wattled-bluelink is also supported by external plumage simi-larities, biogeography, and the propensity of thetwo species to hybridize in the wild (Johnson,1985).

For the Siberian crane, the molecular geneticsstudies (Krajewski, 1989; Krajewski and Fetzner,1994) indicate, as does much of the divergentagonistic repertoire, that the latter species is notclosely related to any other species. Wood’s stud-ies of morphology, however, are largely consistentwith Archibald’s conclusion that the wattled craneis allied with the Siberian crane (Archibald,1976a,b; Wood, 1979). However, one analysisclustered the blue and wattled cranes together.

From our attempt to use behavior to separatespecies and to identify species groups, severalgeneralizations arise. First, most non-socialethons are common to all species (Ellis et al.,1991). In addition, ethons related to rearingyoung, to defending, and to attacking are conser-vative and therefore shared by all species. Asexpected, we found that agonistic displays are lessconservative (i.e. more divergent) and are there-fore more useful in defining taxonomic groups.However even here, comparisons (Table 2) re-vealed very few displays that could, on the basisof presence or absence alone, be used to definetaxonomic groups. Interpretation of results inTable 2 is further confused by the fact that some

displays are closely related to (or arbitrarily sepa-rated from) others with the result that the absenceof one display in one species means very little if asecond species exhibits a display that is obviouslya homologous variant. An example of this are theBill-down displays (Table 2; II, O-R). It is proba-bly of little significance that the crowned cranesdo not have a growl (II, P) component for theirsimilar displays, Bill-down-hold and Bill-down-sweep (II, O and Q), that are almost certainlyhomologs of Bill-down-growl performed by allother species.

The most conspicuous generalizations fromTable 2 are as follows: Copulatory-call (I, P)separates the Eugrus Group from all other cranes.Ventral-preen (II, M) separates the two crownedcranes from all other species. Three displays,Head-lower-ruffle (II, T), Ruffle-bow (II, U), andWing-spread-hold (II, V), together suggest thatcrowned cranes and the Long-train Group arerelated, but separate, from all other cranes. Real-ize, however, that once again II, T and II, U arerelated (i.e. probably homologous) displays. Somedifferences fit no consistent pattern. For example,if the crowned cranes are related to the Long-train Group as suggested by II, M, II, T, and II,V, why do all species except the Long-train Groupexhibit Neck-crane (II, DD)? Some other separa-tions are suggested by the table, but do not meritmention without further study.

Because almost all displays (Table 2) proved tobe common to all species, the differences betweenspecies lie primarily in the expression of displaycomponents not in the presence or absence of thedisplays. These observations, together withArchibald’s success in generating a robust phy-logeny (Archibald, 1976a,b) (later supported bythe molecular studies) using divergent compo-nents of a single social display (the Unison-call),lead us to speculate that detailed comparisons ofthe fine components of at least some of the socialdisplays will in the future prove more useful indefining evolutionary relationships than was pos-sible from our gross treatment of the presence/ab-sence of the displays themselves.

From all molecular and behavioral compari-sons, including this study, it is clear that all butthe African crowned cranes are phylogenetically


very close. Once the African crowned cranes areseparated, the second most distinct group includesthe five species in the Eugrus (Archibald’s 1976aamericana) Group. Strongly suggested is thegrouping of three species in the long-train(Archibald’s 1976a Anthropoides) group. Otherrelationships are still unclear. An important ques-tion involves identifying affinities of the Siberiancrane, and clarifying the relationships between thebrolga and white-naped cranes (C. Krajewski,Personal communication).

Perhaps the most remarkable aspect of the pres-ence-absence data, as presented in Table 2, is thatso many displays are present in all species. Whilewe are fully aware of the potential that interspe-cific similarities may be due to convergence ratherthan descent from a common parent, we assertthat these similarities are so extensive (see discus-sion of criteria for determining homology in Tem-brock, 1963) not only in the form of each display,but also in the context of performance and, just asimportant, in the responses commonly elicited byeach, that our observations support the conceptthat the displays, as described and groupedherein, are true homologs (versus analogs) andsupport the theory that all cranes are closelyrelated. Decades ago, morphological studies ofexternal appearance, osteology, and intrasternaltracheal coiling generated a phylogeny (Peters,1934; Archibald, 1976b; Johnsgard, 1983) that hasbeen little changed by molecular genetics studiesduring the past 10 years (Krajewski, 1989) andlittle altered by our, apparently less powerful,presence/absence data for social displays.

Acknowledgements

At both of our institutions, a host of curators,caretakers, and administrators have made thisstudy possible. To all we offer our thanks. Inparticular, we dedicate this paper to Dr Ray C.Erickson, founder of the endangered species re-search program at Patuxent. Line drawings are byMs. Billi Wagner. Cathy Ellis assisted in all as-pects of manuscript development. J.E.R. Staddongreatly benefitted the manuscript during the re-view process.

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Documents

A sociogram for the cranes of the world · sociogram (sensu Wilson, 1975), a description of all social displays, together with higher level be-havior sequences, here termed activities