WILLIAMS: BREEDING BIOLOGY OF CALIFORNIA QUAIL

THE BREEDING BIOLOGY OF CALIFORNIA QUAIL

IN NEW ZEALAND

O. R. WILLIAMS

Wildlife Service, Department of Internal Affairs, Wellington.

INTRODUCTION

The breeding biology of Lophortyx californicusin North America has been described by Sumner(1935), Olading (1938), Howard and Emlen(1942), Oenelly (1955), Raitt (1960) and Lewin(1963); in the Hawaiian Islands by Schwartz andSchwartz (1949) and in New Zealand by Williams(1952,1959).

Much more local information has now beengathered and this paper is concerned mainly withannual and local variations in the om;et and dura-tion of events in the breeding season, and withannual variations in clutch size. nest success andIhe fertility and hatchability of eggs - all factorsthat might be expected to show correlation withpopulation fluctuations previously described (Wil-liams 1963) which are now known to be no longercyclic (Williams 1966).The following study was made in the central

North Island, near the northern end of LakeTaupo, and in Central Otago in the South Island,within a 40-mile radius of the town of Clyde.

THE REPRODUCTIVE PERIOD

The progress of the breeding season was fol-lowed by using indices of reproductive develop-ment (testis length and diameter of pre-ovulatoryfollicles) direclly correlated with cellular andphysiological changes occurring concurrently inthe gonads. All measurements were made onfresh birds from Central Otago that had beeneither accidentally killed during trapping or shotduring the open season. Not enough birds wereobtained for analysis of variation in onset of thebreeding season caused by age differences. Onefact obvious from Figures 1 and 2 is that quailfirst breed when about 12 months of age.

The testicular cycle

The left testis, generally the larger, wasmeasured to the nearest half millimetre. In itsresting state it has a mean length of about 4 mm.Growth begins in late August; the organ reachesfull size in November, begins to regress in Decem-ber and is back in its resting state by the end of

February (Fig. 1). Assuming that the histologicalstages described by Lewin (1963) for quail inCalifornia, are correlated with the sarno lengthsof testis elsewhere, I.e. that production of maturesperm begins when the testis reaches 7.5-8.0 mm.and ceases upon its regression to 8.0 mm. late inthe breeding season, then both Lewin's (1963)and Oenelly's (1955) Californian data indicatea period of formation of mature sperm of aboutthree months and the local data, four months.These figures may over-estimate the duration ofthe males' true reproductive period. since maturesperms in sufficient number for fertilization maynot be produced immediately.

FIGURE 1. Growth and regression of testes il1 Cali-fornia quail from Central Otago. Data from all

years.

Lewin had enough information to indicatewhether there was likely to be any annual differ-ence in the growth cycle of the testis. He foundno evidence for it over three seasons and con.eluded that the cycle was independent of suchvariables as temperature and rainfall. Becausemales were producing mature sperm three weeksbefore the earliest egg was laid and for a weekafter the laying of the last, Lewin postulated thatthe cycle in males was an adjustment to the morevariable timing of development in females.

Such data as 1 have indicate no difference inthe rate of testis growth and regression betweenadults and immatures (i.e. birds coming intobreeding condition for the first time). This agrees

88

WILLIAMS: BREEDING BIOLOGY OF CALIFORNIA QUAIl.

Neither Raitt (1960) nor Generally have com-Neither Raitt (1960) nor Genelly have com-parable data for California quail but Raitt and'Ohmart (1966) report a 15-week period of sperm- and egg - production in the closely-relatedGambel quail (Lophortyx gambelii).Mackie and Buechner (1963) stated that among

chukar (Alectoris graem chubr) in south-easternWashington males began producing sperm, andfemales eggs at about the same time, but that theperiod of egg production exceeded that of spermby at least three weeks. In this species spermato-genesis lasted about three months and oogenesisabout four. There was no significant differencebetween adults and immatures in the time of onsetor duration of gametogenesis.For North American ring-necked pheasants

(Phasianu~. co/chicus) Kirkpatrick and Andrews(1944) found that rapid development of the testis,as measured by its weight and spermatogenesis.began at about nine months of age. In quail, withmost hatching occurring in Central Otago at aboutmid-December or slightly earlier, a great increasein testis size would have to begin in September ifboth species matured at about the same rate; andthis is what is found. Kirkpatrick and Andrewsreported a second period of advanced growth ofthe testis between 81 and 144 days, followed bya spell of regression. Such was not apparent ineither Lewin's study or my own.

The ovarian cycle

The pattern of the female reproductive cycle inCentral Otago generally agrees with that foundby Lewin who used - as I have done - the tech-nique of measuring the diameter of preovulatoryfollicles. Local data show that the chances offinding an ovum about to be shed increase rapidlyfrom August to a maximum at the end of Octoberand begin to decrease rapidly in late December(Fig. 2). The duration of the laying period is notdirectly measured by this technique because abird may have ovulated and perhaps even laid.This would not be apparent from the graph sincethe next largest follicle now remaining would. beshort of the point of shedding its ovum; and sounless the presence of a post-ovulatory folliclewere observed, the bird would be classified as onewhich had not yet laid. Therefore Lewin's graphand mine do not fix the laying period preciselybut only, perhaps, its minimum duration.Lewin studied growth and regression of two

other structures - the ovary and oviduct, both ofwhich were weighed. All three techniques yieldedsimilar results -laying began at about the end of

FIGURE2. Annual changes in diameter of ovarianfollicles in California quail from Central Otago.

Data from all years.

April and ended in mid-June. Though his graphsgave this mean result (data from all three yearswere pooled), data from individual years showedIhat laying began on 24 April in 1954, 17 May in1955 and 14 May in 1956. The correspondingdates for the end of the laying period were (read-ing from his Fig. 5) approximately 7, 4 and16 June.The duration of only about six weeks in 1954

(Lewin's longest period) seems too short; in 1955it was barely three. The mean of the back-datingmethod (see below) for the two years for whichthere were data was about seven weeks. ForCentral Otago over a ten-year period the meanduration calculated by the same method was 13weeks.Genelly. in his two-year investigation, estim-

ated the period to be II weeks. He classified hensas laying by using a comhination of physicalcharacteristics ~ weight in excess of 200 gms.

condition of the cloaca, spread of the pubic bonesand palpation of the abdomen. Raitt (1960),using palpation in a four-year study, reported aneight-week season but regarded the estimate asa minimum.The occurrence of preovulatory follicles, in at

least some of the Central Otago birds, of diameter8-10 mm. when ova were about to be shed or hadalready been shed seems at variance with Lewin'sgrowth curve for ovarian follicles (his Fig. ll).According to this, a follicle of 8-10 mm. is aboutfive days short of ovulation; yet the rate of egg-laying in California quail is about one per day.My data are insufficient to detect any ditlerence

in the rate of growth of imm"ture and adult gonadsamong females; but such data as there are con~firm Lewin's which suggested that, in spite of

89

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1954-55 , 5.9 15 72 3501955-56 2 7.4 14 219 3871956-57 5 10.2 12 53 3001957-58 5 12.5 12 51 601958-59 t 7.2 14 132 2001959-60 2 7.1 13 205 4401960-61 3 6.9 10 182 2421961-62 I' 6.6 16 253 3201962-63 I 6.6 13 313 4591963-64 3 7.3 II 136 175

WILLIAMS: BREEDING BIOLOGY OF CALIFORNIA QUAIL

diUerences ;n late winter and early spring, bothage groups reached maturity together. Genellypresented evidence, based on only 30 birds overthree seasons, that adults began to lay beforeimmatures and quoted Lchmann's (1953) similarconclusions for bobwhite quail (Co/inus vir-

gil1ial1u.(). Raitt's rcsults on California quail donot imply any clear difference; but he and Ohmart

considered that adult Gambel quail tcnded tostart laying earlier than young of the year.Differences in the time of onset of laying

between yearlings and those breeding for aI leastthe second time have been reported for otherspecies; e.g. for pheasants in New Zealand byWesterskov (1956), who found a consistent differ-ence of about 13 days in both the start of layingand its peak of activity, and by Kluijver (1951)for great tits (l'arus major). In this species adultstended to start laying up to five days beforeyearlings, but the differences were statisticallysignificant in only five years out of nine. It maybe that the type of season (i.e. favourable orunfavourable) has some influence. On the otherhand Richdale (1949) found no such difference inyellow-eyed penguins (Megadyptes antipodes).

THE PHENOLOGY OF BREEDING SEASONS

ANI) ANNUAL VARIATIONS

Dating of events such as laying and hatchingperiods within breeding seasons is important, forthe year-to-year changes in their timing mayinfluence reproductive success (e.g. Lack 1966).There are two methods for establishing the phen-ology of breeding seasons. The more directinvolves careful. intensive and evenly.distributedobservation of a large and representative sampleof nests throughout, at least, the laying period. Butquail nests are hard to find in statistically-usefulnumbers and there is no guarantee that thosefound comprise a random sample. The less directmethod has therefore been used:-Assuming that a representative sample of young

is obtained by trapping and that none has com-pleted the wing moult, the phenology of thebreeding season may be reconstructed from thedistribution of the halching dates found by agingeach bird from the state of moult of its primaries(Williams 1959, Raitt 1961, Taber 1963). Incuba-tion and laying dates may be easily derived sincethey begin 22 and 35 days respectively before thecorresponding hatching date. (Incubation takes22 days and mean clutch size is 13 eggs, laid atapproximately 24-hour intervals (Williams 1952,1966». Figure 3 compares the duration of the

90

FIGURE 3. General breeding seamn phenology inCentral Otago as indicated by (a) growth of firs/-winter primaries of juveniles (solid bars) and(b) growth and regression of the gonads. Verticalson the follicle bar mark the dates at which mostfemale,') were laying; t!lose on the testi~; bar thedates hetween which length was 8 mm. or more.

reproductive period in Central Otago as found byexamination of the gonads with its phenology ascalculated by back-dating. Agreement is satis-factory.In Figures 4 and 5 hatching date distributions

are given for ten seasons in Central Otago and foreight in the central North Island. Theoretically,corrections should be made each yea'r to accountfor actual mean clutch size and mortality of youngproportional to age (Williams 1959). Data neces-sary to make these are not available for mostyears so the distributions have to be used as theystand. Birds aged 0-4 weeks, which might be toosmall to be attracted to, or retained by, trapsneed not be corrected for because they are veryscarce by the time trapping begins in mid-February.

TABLE I. Hatching period data, Central Otago.

Means: 2.4+0.47 7.8+0.69 13.0+0.55

Notes: We.~k No.1 is that of 20-26 October'" One bird hatched two weeks before Week No.1

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1956-57 6 13.0 13 150 4001957-58 3 11.5 14 115 2211958-59 4 lOA 1 I 81 1561959-60 7 11.9 II 113 3421960-61 6 10.7 10 71 1591961-62 2 11.0 17 192 4091962-63 10 13.6 10 71 1071963-64 2 13.4 17 80 195

Means: 5.0+0.92 11.9+0.41 12.9+0.92

Note: Week No.1 is that of 20-26 October.

WILLIAMS: BREEDING BIOLOGY OF CALIFORNIA QUAil.

Weather and breeding season phenology

That significant correlations should exist be-tween various aspects of breeding- and populationphenomena and weather seems incontrovertible.Difficulty lies in trying to find a logical startingpoint for an investigation among the complexinter-relationships of the many aspects of weather.Danger lies in having insufficient biological data.finding (by trial and error) a factor, howeverimprobable, that does have a high correlation withthe particular aspect being studied and then dis-regarding the biased method by which the correla-tion was obtained.

r have not tried to correlate events in thebreeding season with minutiae of such variablesas humidity, sunshine and frost. This is partlybecause preliminary examination of the data indi-cated that chances of finding any significantcorrelations were remote and partly because thelengths of the North and South Island series ofbreeding season data are probably insufficient.Furthermore, quail in Central Otago are obviouslyadapted to an environment different from that inthe central North Island (or elsewhere). Suchdetailed findings as might apply in one regioncould not be anticipated to apply to another.

The main source of weather data has been themonthly summaries of the New Zealand Meteoro-logical Service published in the New ZealandGazette. There, after a brief general survey. rain-fall, temperature, frost, sunshine and other recordsare given and the weather sequence during themonth is described succinctly day by day. Themaps of sunshine-, temperature-, and rainfall-departures from the monthly means have alsobeen used. These are kept at the Weather Officein Wellington. I have here used departures frommeans because I believe that animals would beadapted to means of environmental factors ratherthan to their extremes.

Figure 4 and Table 1 show how very similarmost Central Otago hatching periods are (andtherefore, by implication, the rest of the breedingseasons too) in duration and in the time at whichthe peak and the mean hatching weeks occur; andthis in spite of considerable variation in weathereach year. The central North Island results (Fig. 5and Table 2) are less uniform. Nevertheless, infive of the eight seasons, the mid-point of the meanhatching week jies between 28 December and7 January and the other three between 15-20January. In five of the seven seasons in whicha peak week of hatching occurs it is either that

FIGURE 4. Hatching date histograms, CentralOtago. Vertical bars mark centres of mean h!ltch-

ing week~i.

of 29 December-4 January or 5-11 January. Inboth districts. since the apparent variations intiming of the beginning and ending of the periodsare frequently fixed by the capture of only oneor two birds of a particular age, the magnitudesof these temporal differences are likely to beexaggerated.

TABLE2. Hatching period data, central North Island.

Temperature departure from the mean eF.) Rainfall departures from mean (%)EARLY SEASONS Sept. Oct. Nov. Sept. Oct. Nov.

1954-55 o to +1 o to +1 +3 to +4 -50 ~ 50 - 501958-59 0 +2 +2 to +3 -50 0 - 501961-62 -lto-3 +3 to +4 +1 +50 - 50 to - 75 + 501962-63 o to +1 +1 to +2 o to +1 -33 o to + 50 - 25

"NORMAL" SEASONS1955-56 +1 to +3 +2 to +3 -1 to +1 ~33 -25to-50 o to - 251959-60 +1 to +2 -2 +1 to +2 -33 -25to-50 0

LATE SEASONS1956-57 +1 to +2 +1 o to +1 ~25 o to - 25 +200 to +3001957-58 +1 to +2 -lto-2 -1 to +1 -50 + 50 to +200 +200 to +3001960-61 0 +2 to +3 0 +50 -25to~50 -25to+501963-64 0 +2 -2 to -3 0 0 - 50

Note: o = Mean temperature or rainfall-25 = 25% less than the mean monthly rainfall, etc.

WILI.IAMS: BREEDING BIOLOGY OF CALIFORNIA QUAIL

FIGURE5. Hatching date histograms, central North

Island

Neveftheless, in Tables 3 and 4 I have attemptedan analysis of the effect of spring and early sum-mer rainfall and temperature (the only two factorsthat, on inspection of the records, showed anylikelihood of being significant) on the phenologyof breeding seasons. For Central Otago there issome indication that early seasons tend to followwarmer.than-average Octobers and Novembers,

though this is not confirmed by the central North

Island data. In both districts September weatberappears unimportant. Rainfall greatly in excessof the monthly means during October-Decemberseems as likely to cause heavy mortality amongnewly-hatched chicks as to delay the onset of thebreeding season.

Connexions were 80ught between rainfall dur-

ing the period April-Septemher and the phenologyof the subsequent breeding seasons in CentralOtago. When none was found (Williams 1966)this aspect of the investigation was abandonedafter preliminary examination indicated that thesame result was to be expected from the NorthIsland data.Relying on data from 27 birds over three years

Lewin attempted to correlate variations in onsetof the breeding season with annual variations inrainfall and mean daily temperature in spring. Heconcluded that heavy rain and mean daily tem-perature below 55'F. (13'C.) delayed ovariandevelopment, whereas testicular developmentseemed independent of these variables. His con-clusion may be correct but its exp~rimental basisis slender.

Lack (1966) claimed there was a strong cor-relation between the temperature in March andApril (northern spring) and the date of layingby great tits and suggested that temperature itself,or some factor linked with it, affected not merelybreeding behaviour but also the growth of thegonads. He compared the "warmth sum" (thesum of the 'Co above freezing point of the averagetemperature for each day from I March to 20April) with the mean date of the first egg laideach year. His Figure 5 certainly shows a correla-tion between these two but it is not very con-vincing for warmth sums below approximately325'C. Kluijver (1951), in a similar study,

TABl.E 3. Weather and the onset of Central Otago breeding seasons.

92

WILLIAMS: BREEDING BIOl.OGY OF CAI.IFORNIA QUAIL 93

reported a similar result and later (1952) slatedthat his correlation was one without a causalrelationship.Using less precise data - mean hatching week

and a warmth sum calculated from the mean ofthe daily maxima and minima from three weatherstations in Central Otago (Alexandra, Cromwelland Hawea) for the period I September-20 Octo-ber - I was unable to find any suggestive correla-tion (Fig. 6). I would not claim, as a result, thata correlation between warmth sum and meanhatching week might not be found if other dateswere chosen or if, each year, events in the breedingseason were followed directly instead of by back-dating. On the other hand, spring temperaturesare so much higher in Central Otago than inHolland or Oxford that such a correlation shouldnot, perhaps, be expected.

FIGURE6. Warmth-slim (in of.) for period J Sep-tember-20 Oc/uher and mean hatching week.

Centrul Otago.

DIFfERENCES IN PHENOLOGIES BETWEEN

CENTRAL OTAGO AND CENTRAL

NORTH ISLAND

That central North Island hatching (and there-fore breeding) seasons should start consistentlylater than those in Central Otago and have laterperiods of peak activity (Figs. 4 and 5) runscounter to the general rule that. under normalcircumstances. breeding seasons should be laterin all particulars with increasing latitude. Thedifference should be about 25 days for every tendegrees (Baker 1938). The question arises: Isthe difference between Central Otago and thecentral North Island real and, if so, to what mightit be attributed'!

Westerskov (1956) found the expected relation-ship between latitude and onset of breeding forpheasants in New Zealand and used for his com-parisons direct observations of egg-laying in twogroups in approximately the same latitudes asthe central North Island and Central Otago respec-tively. a difference of about eight degrees. Thedifference between the peaks of the two layingperiods (data from only one season'!) was approxi-mately 21 days and that between slarting datesapproximately 14 days. The birds were game-farm animals: and one might reasonably expectthat. under the circumstances of Jiving in a pro-tective environment, most modifying differences.except that of latitude, would be considerablyreduced, leaving that of latilude paramounL Flux(1966) reported a difference of about a month in theexpected direction between the slart of the breed-ing seasons of song thrushes (TurduJ philomelos)and hlackbirds (T. ",erula) separaled by aboutfive degrees (and a considerable altitude) in NewZealand. But the peaks and the ends of the sea-sons occurred at very similar times. Gurr (1954).on the other hand, did not find that blackbirds inDunedin bred at a time significantly different fromthat in some other parts of New Zealand.

For the two wild quail populations in aboutthe same latitude as Westerskov's pheasants thedifference. over all available years, between themeans of the hatching periods was 4.1 weeks(week 7.8 in Central Otago and 11.9 in the centralNorth Island). This difference is not only in adirection contrary to that expected but is alsostatistically significant (t" = 6.56, P=O.OOI).Because the magnitude of any errors needed

to give a result so much at variance with thatexpected would have had to he so great that itcould hardly have escaped detection, it is simplerand more reasonable to assume the difference is

WII.I.IAMS; BREEDING BIOUX;Y OF CALIFORNIA QUAIL

real and to try to discover a cause. Mean tem-perature appears an unlikely candidate, for that ofthe central North Island is generally higher thanthat of Central Otago. For growth rates of youngto be involved those of Central Otago would needto be higher than those of the central NorthIsland. Though the maximum growth rate (inbody weight) of young Central Otago birds isgreater (Williams ]966) their final body weightis also greater and it is unlikely that the differ-ence between the two rates (even if faithfullyreflected in that of the moult), would be enoughto account for the difference between the twophenologies.

The difference may eventually be eXplained interms of Lack's (1966) suggestion that the imme-diate factor determining the start of breeding isthe obtaining by the female of enough food forcgg formation.

CLUTCH SIZE

Taking as a complete clutch the number ofeggs in a nest that has not been added to in 48hours, I have records of 103 complete clutches inCentra] Otago over all years. Mean clutch size is13.7+0.27 with a range of 8-22. For 16 NorthIsland clutches the mean is 13.00+0.77 with arange of 10-20. (See Table 5 and Fig. 7.) Lewingives a mean clutch size for Californian birds asfourteen. This was estimated from three differentsources: a mean of 13.7 from 16 clutches, a meanof ]1.0 from 40 clutches (Glading 1938). anda mean of ]4.2 from an unstated number. Sincethe mean of the first two sources combined isonly 11.8, his overall mean of 14 would requirethe unstated number to exceed 600. Consideringthe variations given by Lewin and the amount ofannual variation possible in both New Zealandand California, a significant difference betweenmean clutch sizes in the two countries seemsunlikely. Any difference arising from that oflatitude (Lack] 954) if present, is in any event,likely to be small; the mean latitude for the NewZealand quail range is about 4 r S., that of theCalifornian about 370N.

Change in clutch size with advance of the season

Initial laying dates have been calculated for 52nests, either from knowledge of the progresstowards completion of the clutch or from hatch-ing dates of clutches of known size. With datafrom relatively few nests available in anyoneyear 1 have had to combine the Central Otagodata for all years (see Table 6). This means that

the results have to be interpreted cautiously. Asthey stand they indicate a steady falling-off inclutch size throughout the five-month period,though the differences between the means are not

~

significant. This decline with advance of theseason has been reported for other species, forexample, for partridges (Perdix perdix) byJenkins (196]) - an excellent study showing theannual frequencies of clutch size dislributions atsemi-monthly intervals; for American goldfinches(Spinus tristis) by Stokes (1950) - another excel-lent account; for the great tit by Kluijver (1951)and Lack (1956, ]966); for the house sparrow bySummers-Smith (1963) and for the Californiaquail by Glading (1938). who found a mean clutchsize of 12.2 for 26 nests between I May and15 .Iune and a mean of 8.5 for 15 nests begunbetween 16 June and 16 July.

In the present study it is extremely unlikelythat first nestings and re-nestings of individualbirds have been included or second clutches (i.e.those resulting from successfully breeding onceand then re-Iaying), for double brooding appar-ently does not usually occur in California quail(also see Emlen 1939)* nor in some other gamebirds, for example, ruffed grouse (Bonasa umbel-Ius) (Bump et al. ]947), partridges (Jenkins1961), bobwhite quail (Stoddard 1946) andchukar (Mackie and Buechner ]963). Locally,

* A more recent paper by McMil1an (1964) does recorddoublc~brooding, but only as a result o( exceptionalrainfall in a very arid area; and Francis (1965) hasreported double broods in captive quaiL

FIGURE7. Clutch size of California quail in CentralOtago and the central North Island. Data for all

years.

NORTH ISLANDSOUTH ISLAND

94

"NORMAL" TOEARLY SEASONS Oct. Nov. Dec. lal1. Oct. Nov. Dec. Jan.

1957-58 -I to-2 o to +1 -1 to-2 +1 to +2 o 10 + 50 o to + 50 o to + 50 o 10 - 501958-59 +2 to +4 +1 10 +2 +1 t( +2 +3 o 10 + 50 o to - 25 +200 to +400 +1001959-60 o to +1 +, +2 +1 to +2 o to +200 o 10 - 50 -25 to - 50 -501960-61 +2 0 -1 k-3 o to +1 -25 o 10 - 50 -25 to - 50 01961-62 +2 to +4 +1 10 +2 +3 tc. +4 +3 10 +4 -25 to - 50 -25 to - 50 o to - 25 o to + 50

LATE SEASONS1956-57 +1 to +2 0 +1 o to +1 o to + 50 o to + 50 o 10 + 50 -50 10 - 751962-63 +2 to +3 +1 to +2 o 10 +1 o to +1 o to + 50 +50 +150 to +300 -25 to - 501963-64 +1 to +2 -1 to-2 -1 -210 -3 -10 to - 50 -25 to - 100 0 -25 to -100

SEASON 1949-50 1953-54 1954-55 1955-56 1956-57 1957-58 1958-59 1959-60 1960-61 1963-64 MeanClutch size 11.7+0.83 13.1 +0.83 13.6+0.73 14.0",0.85 14.2+0.71 11.8+0.65 12.4+0.61 13.3+0.63 14.0+ 1.27 10.7+0.72 13.2(No. in sample) (7) (14) (19) (10) (12) (3) (11) (19) (4) (3)% Nest success 57.1 14.3 87.5 40.0 83.3 0 100.0 78.9 - 0 62.6

(7) (7) (8) (5) (6) (2) (3) (19) (0) (2)

'Ie deserted 14.3 71.4 0 20.0 16.6 50.0 0 5.3 - 50.0 18.7

(7) (7) (8) (5) (6) (2) (3) (19) (0) (2)% predated 28.6 14.3 12.5 40.0 0 50.0 0 0 - 50.0 18.7

(7) (7) (8) (5) (6) (2) (3) (19) (0) (2)% hatchability 74.1 84.7 97.7 88.0 100.0 - 100.0 99.4 - - 96.0

(31 ) (13) (87) (25) (68) (0) (37) (135) (0) (0)

% fertility 83.0 91.4 98.8 88.0 97.1 100.0 100.0 92.0 - - 93.8(47) (35) (87) (25) (70) (24) (37) (176) (0) (0)

Mean hatchingweek - - 5.9 7.4 10.2 12.5 7.2 7.1 6.9 7.3 -Subsequent shoot~iog age ratio 49 85 195 268 164 53 175 181 171 93 -(young per adultfemale)

TABLE4. Weather and the onset of central North Island breeding seawns.

Temperature departures from the mean CF.) Rainfall departures from mean (%)

N ole: 0 means mean temperature or rainfall.

-25 means 25% less than mean monthly rainfall, etc.

TABLE5. Breeding season data, Central Otago (nests of known fate).

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TABLE6. Variation of clutch size with advance of the season (all years).

LAYING DATE FREQUENCIES OF CLUTCH SIZE MEAN S.E.

9 10 II 12 13 14 15 16 17 18 18+1-30 Sept. 0 0 I 0 0 1 0 2 0 0 0 14.3 1.02

1-31 Oct. I 2 J 3 I I 0 1 I 2 1(22) 13.5 0.89

1-30 Nov. 1 2 4 3 4 2 3 0 I o . 0 12.6 0.371-31 Dec. 0 2 I 2 2 0 I 1 0 0 0 12.4 0.741-31 Jan. 0 2 I 0 0 0 0 0 0 0 0 IOJ 0.55

TOTALS: 2 8 10 8 7 4 4 4 2 2 I 12.8

96 WII.LlAMS: BREEDING BIOLOGY OF CALIFORNIA QUAIL

more observation8 of change in clutch size wilhtime are needed, especially observations withinone particular year. But there is little doubt thatthe trend will be confirmed.

The implication is that, all other things remain-ing equal, the later the breeding season withina particular locality the less successful will it be;a general conclusion also reached by Lack (1966).When mean clutch sizes of a species are beingcompared from place to place and from year toyear account should obviously be taken, wheneverpossible, of at least the mean hatching dates of theseason. Such data are only very rarely available.For annual mean hatching dates in New Zealandsee Tables I and 2.

Annual variation in clutch size

Over ten years mean annual clutch sizes forCentral Otago have ranged from 10.7 to 14.2 (seeTable 5). Differences between years are notsignificant (some years have very small samplesizes), nor are there any statistically-significantcorrelations between annual mean clutch sizes andeither breeding season phenologies or estimatesof productivity such as age ratios found either attrapping in March or during the shooting seaSon(Williams 1966). However, higher clutch sizesat least tend to be associated with higher ageratios and vice-versa, as Lack (1964) found forthe great tit in a 17-year study and Jenkins, Watsonand Miller (1963) for the red grouse (Lagopus I.scoticus) in Scotland over a five-year period. Inmy own study, even if the differences between allannual mean clutch sizes were significant. jnspec~tion will show that these differences could notalone be responsible for the annual differences inmean age ratios. 1 agree with the concJusionsreached by Jenkins after a four-year investigationof population control in partridges: "With highnest losses and, particularly with a high mortalityrate among newly hatched chicks, the small differ-ences noted in clutch size [only 15.5 to 16.6] haverather little importance from the yiewpoint ofpopulation control".

NEST SUCCESS

The criteria used for determining this statisticshow considerable variation. Among the possibleare:-

(i) The percentage of totally successfulnests (i.e. those from which all younghatch).

(ii) The percentage of nests from which atleast one egg has hatched.

(iii) The percentage of nests from which atleast one egg has hatched of all thosenests in which the clutch was known to becomplete.

(iv) The percentage of nests from which atleast one egg has hatched of all thosenests in which not only was the clutchknown to be complete but whose ultimatefate was also known.

Of all the possibilities (ii) seems to be the onein commonest use and was the one used byGlading to obtain a figure of 18% for Californiaquail in a study lasting only one season. Thoughnot explicitly stated, Jenkins, Watson and Millerapparently used (iv) for their red grouse. Thisshould be the measure of nest success used when-ever possible, though it is the hardest to obtain.Only complete clutches should be used since nestsabandoned or destroyed during laying are likelyto be replaced and so will be unimportant in anydetermination of subequent population size. Onlynests of known fate should be used otherwise nestsuccess is underestimated since nests of unknownfate -are, in effect, classed as unsuccessful. Com-parisons of nest success such as those made byHickey (1955) lose most of their value because oflack of consistency in the standard, as Hickeyhimself recognized. I have used the term "nestsuccess" instead of the more usual "nesting suc.cess" because the meaning seems more precise,implying the success of the nest and its contentsrather than success in making a nest and depositingeggs in it.Over all years nest success in Central Otago was

62.6% (Table 5). Expressed on a monthly basisit reached an apparent peak in November (Tabl~

Number ofnests 4 14 17 9 3 12

% successful 50.0 50.0 765 44.4 66.7 75.0

WILLIAMS: BREEDING BIOLOOY OF CALIFORNIA QUAIL 97

7); and although, once again, the smallness of thesample warns that the results must be interpretedcautiously, they parallel Glading's which indicatedthat nest success was at a maximum at a corres-ponding time.

TABLE7. Percentage of complete clutches of known

fate from which at least one egg hatched.

Sept. Oct. Nov. Dec. Jan. Undated

Cause!J'of nest losses

Of the 103 nests with complete clutches inCentral Otago, the ultimate fate of 43 is unknown.Of the remaining 59 we have just seen that 37 weresuccessful. Eleven were deserted, generally as aresult of examination early in the incubationperiod or through other disturbance by man ordog. The remaining II were destroyed either bypredation of hen or eggs, or by such agents asfire. agricultural activities and, in one instance,robbery by man. Predators were known to be orassumed to be either feral domestic cats or suchintroduced carnivores as ferrets, stoats or hedge-hogs. With relatively few records there is littlejustification for any further quantitative discussionof the causes of desertion or destruction.Worth mentioning is the suggestion by Jenkins,

Watson and Miller that among red grouse incertain years variations in behaviour, perhapsarising from psychological changes dependent ondensity-governing factors, may affect a bird'sliability to desert its nest or neglect its young.

FERTILITY OF EGGS

In Central Otago there is no common trend orcorrelation between annual estimates of egg fer-tility and any population index. Fertile eggs aredefined as those from which chicks have hatchedor in which dead embryos have been found. Inthis investigation estimates of annual percentageof fertility are likely to be minima since anyuntrained observers in the nest recording schemecould be expected to overlook embryos dying inthe earliest stages of development either throughdesertion, accident or genetic causes. The annualrange was between 83.0% and 100%, the meanfor all years being 93.8% (see Table 5).Data on annual fluctuations in fertility are not

common in the literature. Jenkins, in his study,reported that few partridge eggs proved infertile:

of 41 that failed to hatch and were examined,only three - all from the same clutch - did notcontain embryos. And over three seasons lossesthrough infertility and death of embryos combineddid not exceed 10%. In their red grouse investi-gation Jenkins, Watson and Miller found 28% of94 unhatched eggs were infertile in two yearsof population decline but that none out of 78examined was infertile in three of the good years.In general, fertility of game bird eggs is high:

Stoddart (1946) found only 5.26% addled orinfertile out of 2,874 bobwhite quail eggs examinedover four years. Middleton (1935) recorded that,over a number of years in England, 93% of nearly60,000 common partridge eggs hatched. Of theremainder he remarked, "some are infertile, butothers have been arrested in development duringincubation or contain chicks which have died inthe shell when ready to hatch". In New Zealand,Westerskov found 96% of eggs of wild pheasantswere fertile, those from captive birds being only89% so.

HATCHABILITY

Another variable affecting population recruit-ment is hatchability. This is to be distinguishedfrom nest success which is affected by circum-stances beyond the eggs themselves and theembryos they contain. By hatchability is meantIhe proportion of fertile eggs hatching from suc-cessfully incubated nests: it is, in effect, a measureof viability of the embryo - a property one mightwell expect to show some correlation with popula-tion density, being perhaps congenitally deter-mined, as implicit in the ideas of Chitty (1960)and Pimentel (1961).Because of the difficulties encountered in this

study in obtaining a large amount of breedingseason data, it has not always been possible tousefully separate information on hatchability ashere defined from hatchability plus egg fertility.In the following brief discussion on annual varia.tions in hatchability and changes in this propertywHh advance of the breeding season, infertile eggsare included. since observers other than myselfhave not always distinguished between these andembryos dead in the shell. As far as annualvariations are concerned there is no clear con-nexion between apparent hatchability and popu1a-tion level (Table 5) except that hatchability waslow in two of the trough years. However, it wasnot significantly higher in the breeding seasonimmediately preceding the 1956 peak than it wasin the season that ushered in the 1954 "low".

TABLE8. Variation of hatchability plus fertility of

eggs with advance of the season (Cel1tral Otagoall years).

Sept. Oct. Nov. Dec. Jan. Overall

No. of eggs 30 79 163 50 21 343% hatch. 100 92.4 88.3 88.0 80.8 89.8

98 Wn.LlAMS: BREEDING BIOLOGY OF CALIFORNIA QUAIL

Within the breeding season the trend of thechange in hatchability is parallel with that ofclutch size though the values for each monthare not significantly different from each other(Table 8).

Glading reported that 163 chicks hatched from181 eggs during one season, a hatchability of Cali-fornia quail, in the sense used in Table 8, of90.1%.Jenkins, Watson and Miller calculated hatching

success as the percentage of eggs hatching afterdeduction of losses through desertion and faultyincubation. Losses from predation had alreadybeen subtracted from the total number laid in eachseason. Hatching success so calculated (whichapparently included jnfertile eggs and deadembryos) showed an annual variation over fiveyears from 70% to 95% (mean 82.4%) and wasat its lowest in the year of smallest population.Lack (1954) discussed hatching success but cal-

culated success from data combining "(a) pro-portion of nests totally destroyed, (b) proportionof eggs failing to hatch in nests where at leastsome hatched". His percentages of success were,of course, generally low, as would be expectedfrom such treatment in which unhatched eggsinclude losses through accident, predation, deser-tion, infertility and embryo mortality. His discus-sion emphasizes the overall differences in earlymortality between nidicolous and nidifugousspecies but does little else.

CONCLUSION

Apart from an unexplained difference in timing.contrary to that expected, between the breedingseasons of California quail in the central Southand North Islands, seasons are little different intheir most important aspects from those in othercountries where the species occurs.Population fluctuations (as measured by age

ratios) are not closely correlated with annualvariations in climate, breeding season phenologyor with the different components of reproductiverate. However, the absence of at least some cor-relations may result from paucity of some neces-sary data. '

,.

Whether density-dependent mortality induced,for example, by food shortage beyond the breedingseason, has brought about regulation of numbers- a situation Lack (1966) suggests is usual amongbirds - is a topic to be discussed elsewhere.

ACKNOWLEDGEMENTS

I am grateful to my Research Section collc3gues forcriticisms and suggestions, to members of the Field Stafffor assistance over many years and to Mrs. HelenMorrison for drawing most of the figures. Much of thework in Central Otago was done on the properties ofMessrs. H. Holloway at Cairnmuir and C. Jelley atLuggate. I am deeply indebted to them for their long~continued hospitality.

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