72 JEFFERY HARRISON : BREEDING PLUMAGE OP WADERS IBIS, 90

T H E BREEDING PLUMAGE OF SOME WESTERN PALIEARCTIC WADING BIRDS.

By JEFFERY HARRISON.

Received on 7 February 1946.

INTRODUCTION. This large group of birds has always been a favourite one with ornithologists,

both from the scientific point of view, and also from the zsthetic side, on account of their extreme grace of form and their striking and handsome spring plumages. Although a certain amount has been written on the spring plumages of individual species in this group, I have not yet come across any work which has taken into consideration the spring plumages of the group as a whole. This has rather surprised me, considering that it has so striking a spring plumage and so wide a breeding range, which enable the observer to study any effects of varied climatic conditions upon the breeding plumage.

Types of breeding plumage among species. In the western Palaearctic region, wading birds may be broadly divided into three main groups, according to the types of breeding plumage that they assume, and this can be correlated with their breeding distribution over a north-to-south range. The groups can be designated as a northern, an intertfiediate and a southern group. They are of course somewhat artificial, and there is naturally some overlap at either end.

The northern group, those having their main breeding area in or near the Arctic Circle, in latitude 65" or over, includes such species as the Bar-tailed Godwit Limosa lapponica, Knot Calidris canutus, Curlew-Sandpiper Calidris testacea, Grey Plover Squaturola squatarola, Grey Phalarope Phaluropus fulkurius, Turnstone Arenaria interpres, and Sanderling Crocethia albu.

Apart from the last two rather exceptional species, this group has much in common with regard to the spring plumage :-

(a) The moult is complete, and the plumage assumed is completely different from the winter one.

(6 ) The plumage is highly pigmented. (c) The ventral surfaces of the birds concerned tend to become as dark

( d ) The colours mainly concerned are blacks, greys and red-browns.

Dark ventral surfaces occur in some species in the intermediate group as well, for example, the Spotted Redshank and the Dunlin. This is a condition quite contrary to the normal counter-shading which is seen in

as their backs, or even darker, as in the case of the Grey Plover.

1948 IEFFERY HARRISON : BREEDING PLUMAGE OF WADERS 73

almost all species of birds, and, indeed, in the waders under consideration, in their winter plumages. In these the back is darker than the underparts, and is an important factor in protective coloration.

The intermediate group includes all those species which have their main breeding distribution from latitude 65" southward to latitude 45" in the Mediterranean area. Included in this group are :-

Black-tailed Godwit Limosa limosa, Curlew Numenius arquata, Whimbrel Numenius phreopus, the snipes Capella and Lymnocryptes, Red-necked Phalarope Phahropus lobatus, Dunlin * Calidris alpina, Little Stint Calidris minuta, Temminck's Stint Calidris temmiwkii, Ruff * Philoniachus pugnax, Common Sandpiper Actitis hypoleucos, Wood Sandpiper Tringa glareola, Green Sandpiper Tringa ochropus, Redshank Tringa totanus, Spotted Redshank * Tringa erythropus, Greenshank Tringa nebulariu, Ringed Plover Chardrius hiatinrla, Little Ringed Plover Churadrius dubius, Kentish Plover Leucopolius alexandrinus, Golden Plover * Pluvialis apricaria, Lapwing Vanellits vanellus, and the Oystercatcher Himantopus ostralegus.

Species marked * assume a breeding p!umage somewhat similar to those species in the northern group already described, while the remainder tend to assume a far less elaborate spring dress, mostly distributed on the flanks, head, neck and back, leaving the ventral surface light. Species placed in the same genus, but put by me into the two different breeding groups, give good examples of the type of plumage so far described-for instance, Black and Bar-tailed Godwits and Red-necked and Grey Phalaropes.

A few species placed by me in the intermediate group resemble the southern group in having a summer plumage almost identical with their winter one, examples being the Little Ringed Plover and the Kentish Plover, which could easily be included in either group.

The southern group includes all those species whose main breeding area is south of latitude 45", and includes among others such species as the Black- winged Stilt Himantopus himantopus, Avocet Recumirostra avosetta, Pratincole Glareola pratincola, Black-winged Pratincole Glareola nordmanni, Cream- coloured Courser Cursorius cursor, Spur-winged Plover Hoplopterus spinosus. The characteristic of all the waders in this group is that they have a summer plumage which is almost identical with their winter one.

Several of the species at present under consideration have been divided into subspecies which show a north-to-south differentiation, or cline, with dark forms in the north and light forms in the south. As would be expected, the differences are not so marked as between species placed in different groups, but I consider that they are comparable and relate to the same general phenomenon. Such examples are the Northern and Southern Golden Plovers Pluvialis apricmia altifrons and aprimria, Arctic and Ringed Plovers Charadrius hiaticula tundra and hiatimla, Lapland and Southern Dunlin Calidvis alpina alpina

Types of breeding plumage among subspecies.

74 JEPFERY HARRISON : BREEDING PLUMAGE OF WADERS IBIS, 90

and schinaii and the Iceland and British Kedshanks Tringa totanus r&ta and britcmnica.

In addition, it is interesting to note that, as shown by Dr. J. M. Harrison, the Continental Redshank Tringu t. iotunus tends to be dimorphic, with a dark form more plentiful in the north of the breeding range, and a light form more plentiful in the south.

Spring moult tends to become more complete and the plumage increasingly darker and more highly pigmented from south to north. This is seen best in species, but is also seen in sub- species, and in one species with a dimorphic variation. The distribution of the pigment is such that the ventral surface tends to become as dark as the back, or darker, in the more northerly latitudes.

The different climatic conditions should be mentioned, as they must have a considerable effect on the birds. The three areas which correspond to the breeding areas of my three groups of wading birds are :-

(a) The Arctic-Northern Scandinavia, Spitzbergen, Novaya Zembla etc. In these areas, the spring is late and cold and the summer very short, but it is warm inland. The length of day alters very rapidly. The north and north-east Norwegian coasts are less inhospitable than any other areas in so high a latitude, but in Spitzbergen even in the height of summer the temperature is only around 3 5 4 0 ° F . Snowfall is frequent in all Arctic regions.

On the whole, spring is warm and moderately dry, although rainfall is frequent but not heavy. The length of day alters far less rapidly than in the Arctic.

(c ) Spain and the Mediterranean area. Dry and hot, all seasons being characterized by much sunshine and a low rainfall.

From south to north, the onset of spring is later, avarage temperatures decrease, rainfall increases, and alterations in the length of daylight become more rapid.

Summmy of types of breeding plumage.

Climatic conditions in spring.

(b) The British Isles, Northern France, the Low Countries etc.

DISCUSSION. The whole question of the control and function of spring plumage in the

wading birds at present under consideration is a very complicated one, and one that would make an interesting piece of research work for the future. Before ending this paper, there are one or two points which I would like briefly to mention.

Dementiev and Larionov (1945) have shown that geographical changes in colour such as 1 have described are due to the deposition of melanin in the feathers, the different colours being derived by different degrees of oxidation

1948 JEFFERY HARRISON : BREEDING PLUMAGE OF WADERS 75

from a single colourless pre-pigment, melanogen. Thus, in my three groups, there are three types of plumages all due to the same pigment, but in different degrees of oxidation. These differences, now inherent, are presumably related to the differing external stimuli to which the birds have been sub- jected.

Another important point is the effect of temperature. Waders that breed in low-temperature areas, in common with other species, show vaflious adaptations io enable them to maintain their body temperature. Birds of more northern populations have a comparatively larger body-size (Bergman’s rule), and therefore a relatively smaller surface area from which to give out heat. Thus, the Iceland Redshank is one of the largest races of the species. Similarly, Hesse’s Quotient is a manifestation of a relatively large heart in animals inhabiting cold and mountainous districts.

It is difficult to see any reason for the very unusual and characteristic spring plumages of the northern group of wading birds, and yet, for so many to “ arrive at the same answer ” and have either a chestnut or a black breast makes it obvious that there must be some very good reason. That it has developed independently in so many species means that, as pointed out to me by David Lack, there must be a survival value attached to it. In his view, this can only be associated with protective coloration. I do not think that this is necessarily so, because it goes against the normal counter-shading of a bird, and so tends to make it more conspicuous ; and at times when it needs to appear as inconspicuous as possible it is either sitting on the nest or else crouching, and so obliterating any protective coloration that there may be on the breast. However, it is possible that counter-shading is dot of such significance in the Arctic as in other zones. I would suggest that the dark underparts may have a survival value, in that they enable the bird to maintain its body temperature by absorbing not only direct heat but also heat reflected from the earth. This method of absorbing heat does not operate when the bird fluffs itself out and causes itself to be surrounded with a layer of air, which not only prevents heat loss, but heat gain as well.

ACKNOWLEDGMENTS. I am most grateful to my father, Dr. J, M. Harrison, Mr. David Lack and Mr. K. E.

Moreau for giving me their advice and criticism in the preparation of this paper, and also to my father for the use of a large number of skins.

SUM IVIARY.

(1) There is a tendency for the more northern breeding waders to have darker and more elaborate spring plumage.

(2) Over the breeding range considered, three geographical zones have been distinguished, in which the coloration of waders of different species shows similarities ( I ‘ ecological isomorphism ”).

(3) The dark underparts of northern breeding waders are may br concerned with heat absorption or protection, and must bc considered with Bergman’s Rule and Hesse’s Quotient.

76 M. F. M. MEIKLEJOHN : BIRDS OF TEHERAN AND ALBORZ IBIS, 90 BIBLIOGRAPHY.

DEMENTIEV, G. P., and LAHIONOV, V. F. (1945). ‘ The development of geographical Proc. Zool. SOC. London,

‘ Some remarks on the Western Palearctic races of Tringa

Proc. Eighth

colour variations, with special reference to birds.’ 115 : 85.

totanw (Linnaeus).’ Ibis, 86 : 493.

Internat. Om. Congr. Oxford : 430.

HARRISON, J. M. (1944).

HUXLEY, J. S. (1938). ‘Threat and warning coloration in birds.’

SUMMER NOTES ON BIRDS OF TEHERAN AND THE ALBORZ MOUNTAINS * By M. F. M. MEIKLEJOHN.

Received on 2 December 1946.

The following is a record of birds observed during a summer spent in Teheran, from 6 May to 8 August 1946. All is based upon sight records, but, whenever there has been any doubt as to the identification of a species, that doubt will be reflected in the text.

Teheran forms an oasis of gardens in a semi-desert, across which the main roads run east to Ab Ali, and west to Karaj and so to Qazvin. In the semi-desert area my observations were extremely limited, being only undertaken in journeys along the main roads on the way to other places. The typical birds of the area are Crested Lark, Isabelline Wheatear, Hoopoe, Common Bee-eater, Roller, Littleawl and Kestrel; it also forms a feeding ground for Rooks.

The city itself, on account of its abundant water supply and large gardens, is rich in birds. Of migrants on passage the Common Redstart and Spotted Flycatcher were seen, and regularly throughout the summer such vegetation- loving species as the Olivaceous Warbler, Blackbird, Nightingale, Syrian Woodpecker and Hobby.

To the north of Teheran, at its nearest point about six miles away, stretches the range of the Alborz. As is well known, the Caspian slopes of these mountains (which were never visited by me) are clothed in thick vegetation, while the southern slopes are almost entirely barren; but, although from Teheran little can be observed on the mountains but bare rock, when the valleys are reached they are found to be well provided with gardens of mulberries, grove8 of walnuts, poplars and willows, with occasional wild cherry trees, dogwood and hawthorn. The trees, except in the wider valleys, usually come to an end at about 6000 ft., the willow being generally that which grows at the highest altitude. Familiar European wild and

* I shall use the form “Alborz” throughout, in place of the unphonetic form *‘‘ Elburz ” usually found on British maps.