J . Zool., Lond. (1990) 220, 333-343

Behaviour of the yellow-eyed penguin chick

PHILIP J. SEDDON*

Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand

(Accepted 14 February 1989)

(With 1 plate in the text)

The ontogeny of yellow-eyed penguin (Megadyptes antipodes) chick behaviour follows the order ofdevelopment determined by Nice (1962) for several species of birds, and by Spurr (1975) for the Adelie penguin (Pygoscelis adeliae). Feeding and comfort behaviours are the first to develop, followed by locomotion and aggressive behaviour.

Active solicitation of food may occur at one day of age. Chicks initially use non-visual cues to mediate begging. After their eyes open on the third or fourth day there is an increase in the use of visual stimuli, and begging occurs most often following adult nest relief. Sibling rivalry is not intense, occurring least during feeding, and in general both chicks are fed at each session.

The chicks are brooded for the first 21-25 days. At sparsely vegetated nest sites overheating may occur after 21 days and down-covered chicks will seek shade and pant in hot weather.

Throughout the 6-7 weeks of the guard phase there is a decrease in the amount of time spent resting in a prone posture, and an increase in exploratory, locomotory behaviour. During the post-guard phase, and until fledging and independence at 15 weeks after hatching, chicks may wander up to 20 m from the nest bowl during exploration, shade-seeking and feeding.

Adults feed only their own chicks, and chicks appear to beg only from their parents. Dense vegetation and long distances between nests tend to restrict contact between adults and chicks from neighbouring nests, and prevent the formation of large chick crkhes.

Introduction . . . . . . Methods . . . . . . . .

Observations . . . . . . Behaviours . . . . . .

Results and discussion . . Posture and locomotion Thermoregulation . . . . Feeding . . . . . . . . Comfort behaviour . . Aggression . . . . . . Parent-chick recognition

Summary . . . . . . . . References . . . . . . . .

Contents

Page . . . . . . . . . . . . . . . . . . . . . . . . . 334 . . . . . . . . . . . . . . . . . . . . . . . . . 334 . . . . . . . . . . . . . . . . . . . . . . . . . 334 . . . . . . . . . . . . . . . . . . . . . . . . . . 335 . . . . . . . . . . . . . . . . . . . . . . . . . . 335 . . . . . . . . . . . . . . . . . . . . . . . . . . 335 . . . . . . . . . . . . . . . . . . . . . . . . . . 337 . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 . . . . . . . . . . . . . . . . . . . . . . . . . . 340 . . . . . . . . . . . . . . . . . . . . . . . . . . 340 . . . . . . . . . . . . . . . . . . . . . . . . . . 341 . . . . . . . . . . . . . . . . . . . . . . . . . . 342 . . . . . . . . . . . . . . . . . . . . . . . . . . 342

* Present address: P.F.I.A.O., University of Cape Town, Rondebosch 7700, Cape Town, South Africa

333 0952-8369/90/002333 + 1 I $03.00 0 1990 The Zoological Society of London

334 P. J . SEDDON

Introduction

The study of the early ontogeny of animals allows us to examine the development of natural behaviour in an uncontaminated form (Khayutin, 1985). The concept of systemogenesis (Anokhin, 1964) states that behaviour is a relationship between organism and environment. Thus any study of the early forms of behaviour and their development must relate changes to the interaction of the animal and its surroundings.

Yellow-eyed penguin (Megadyptes antipodes) chicks are semi-altricial when they hatch. The period of parental care may be divided into the guard phase, when chicks are constantly attended by a parent, and the post-guard phase, when chicks are unguarded during the day while both parents feed at sea. Chicks depart for sea and become fully independent at approximately 106 days of age.

Yellow-eyed penguin chick growth, plumage changes and some specific behaviours have been described by Richdale (1957), but no detailed study of the development of their behaviour has been made, nor has chick behaviour been related to the surrounding habitat. Yellow-eyed penguins breed on the south-east coast of New Zealand’s South Island, on Stewart Island, and in the Auckland and Campbell Island groups. Nests are sited beneath dense vegetation, with up to 150 m between neighbouring nests. The wide space between nests and the use of heavily vegetated breeding areas will produce marked differences between the behaviour of the yellow-eyed penguin chick and that of the more colonial Antarctic penguins. Spurr (1975) gave a detailed account of the behavioural development of the Ad& penguin (Pygoscelis adeZiae) chick, describing the developmental stages using the framework formed by Nice (1 962).

This paper describes the development of the behaviour of the yellow-eyed penguin chick, using the same approach as Spurr (1975) to facilitate comparisons.

Methods

Observations

Observations were made over 3 breeding seasons on the Otago Peninsula, Dunedin, New Zealand. In the 1984-85 and 1986-87 summers, nests were checked daily and individual chicks were observed from the time of hatching to fledging. In the 1985-86 summer, daily checks and 2-10 min observations were made at marked nests at 2-5 day intervals. At a sample of marked nests (Table I) 1-min scan sampling (Altmann, 1974) was used to record chick behaviour during 30-min t o 12-h observation periods.

TABLE I Sample sizes for yellow-eyed penguin chick time budget

during the guard phase

Number of Number of Minutes of Days nests chicks observation

1-10 7 14 6360 11-20 4 8 2010 21-30 6 12 3220 31-40+ 4 8 3220

YELLOW-EYED PENGUIN CHICK BEHAVIOUR 335

A total of 14810 min of observations was made from hatching to the beginning of the post-guard phase. Increased chick mobility and the density of the vegetation surrounding nest sites made observation throughout the post-guard impractical.

Behaviours

Posture -upright: body erect, including 'corpulent posture' (Richdale, 1957: sitting back on tarsi, body erect, belly

-half-prone: body 2545" to the ground, seen during shuffling movements by very young chicks, or later

-prone: body horizontal, on the ground or against sibling; the most common resting posture.

resting on the ground).

during begging.

Sleeping: eyes closed, often prone. Quiet awake: eyes open, but no body movement. Locomotory: all unforced and apparently undirected locomotory movements. Comfort: all shaking, stretching and preening movements (McKinney, 1965; Ainley, 1974). Begging: active solicitation for food, including bill-shaking, peeping call and food-swallowing. Stick-biting: gripping of the nest material or vegetation surrounding the nest. Fight sibling: pecking, bill-gripping and flipper-striking directed against sib. Allopreening: any nibble preening (Ainley, 1974) of any part of sibling or parent.

Results and discussion

Posture and locomotion

The amount of time spent in an upright posture increased with age, with a consequent decrease in half-prone posture (Table 11).

Changes in posture reflect changes in the coordination of body movements, the development of locomotion, changes in the form of comfort behaviours and the onset of thermal independence. During the course of the guard phase there was a decrease in the amount of time spent resting as chicks became generally more alert and active. The activity budget for guard phase chicks is set out in Table 111, and the ages at which behaviours were first performed by chicks are presented in Table IV.

The newly hatched chick lies fully prone beneath the brooding adult. In the first three days movements are largely restricted to position shifts and begging, both of which involve the uncoordinated raising of the head. After a week a half-prone posture is adopted during begging;

TABLE I1 Percentage of time spent upright, half-prone andprone by

yellow-eyed penguin chicks during the guard phase

Days of guard phase

Posture 1-10 11-20 21-30 3140+

Upright 1.9 8.1 7.8 20.1 Half-prone 6.9 0.8 0.5 0.1 Prone 91.2 91.1 91.7 79.8

336 P. J. SEDDON

TABLE I11 Activity budget for yellow-eyed penguin chicks during the guard phase. Figures are percentages of total observation

time for each 10-day interval

Days of guard phase

Activity 1-10 11-20 21-30 31-40-t

Sleeping Quiet awake Locomotory Comfort Begging Stick-biting Fighting sib. Preening adult Preening sib.

Total

92.0 0.7 0.0 3.4 3.8 0.1 0.0 0.0 0.0

100

85.2 4.5 0.0 4.1 5.7 0.5 0.0 0.0 0.0

100

78.9 13.8 1.1 4.6 0.5 0.2 0.8 0.1 0.0

100

78.2 13.0 0.4 6.6 1 .o 0.1 0.5 0.1 0.1

100

TABLE IV Age of yellow-eyed penguin chicks at which behavioursfirst recorded

0-5 Completely brooded-hidden by parent. Beg with peeping call and beak movements. Shuffle movements; raise head; shrill distress call. Some comfort movements-yawn, head-shake.

6-10 Adult lies over the top of both chicks. Beg in half-prone or upright posture. Bite at sticks and nest material. More comfort movements-wing-stretch, tail-wag, swallowing, sneeze, and defecate over the nest edge.

11-15 Adult lies over one chick or between both, chicks tend to orient heads under brood patch. Harsh aggressive call first heard. Crawl around nest, or assume the ‘corpulent posture’. Head-scratch with foot over flipper.

16-20 Adult lies on or against chicks. Freely move around nest, ‘corpulent posture’ common. Fight with sibling- pecking and beak-gripping. Rapid-wing-flap and both-wing-stretch.

21-25 Lie with head under adult, or next to sibling. Homeothermy developed4hicks pant and seek shade. ‘Corpulent posture’ mainly, but able to stand off tarsi. Fight with sibling-flipper-hitting.

26-30 Lie prone away from adult, occasionally preen adult. Walk close to the nest bowl (< 2 m). Increased exploratory behaviour, e.g. fly chasing.

31-35 Increased mobility around the nest (2-5 m) to seek shade. May preen sibling.

36-40 Mobility increases. Some chicks left unguarded.

41-45 Many left unguarded

46-50 All left unguarded, may move seawards.

YELLOW-EYED PENGUIN CHICK BEHAVIOUR 337

this posture persists throughout the chick phase, allowing the chick to place head and bill below that of the adult. The first upright posture, the corpulent posture (Richdale, 1957), is seen after two weeks when the feet and protruding belly are used for tripod support. The chick at this time is not able to stand up off the tarsi. A fully upright posture (Plate Ib) occurs after about 21 days during resting, exploratory and locomotory behaviour and when pecking or flipper-hitting a sibling. Exploratory behaviour occurs after two weeks and is confined largely to the nest bowl until 32 days ( f 5.6, n = 53) (Table IV), and usually within 5 m of the nest bowl for the remainder of the guard phase. During the post-guard phase, exploration, shade seeking and a general move towards the sea mean that chicks may wander up to 20 m from the original nest bowl (Table V).

Thermoregulation

Yellow-eyed penguin chicks are constantly brooded from the time they hatch until they are 21- 25 days of age. In the first week the chicks are incubated like eggs and are fully covered for more than 90% of the time, but rapid growth means that by the end of the second week the brooding adult cannot cover them and lies between or against them (Table IV). Chick insulation increases with age, with the sparse primary down (Plate Ia) being replaced with dense secondary down (Plate Ib) from day 7. The chicks are covered in secondary down by day 20 and will pant but are not yet able to control heat loss. Chinstrap and gentoo penguin chicks have a high thermogenic capacity by the tenth day, five days before they become homeothermic (J. R. E. Taylor, 1985). The clearance of much of the traditional coastal forest nesting habitat along the south-east coast of the South Island has exposed breeding penguins to the warm temperate climate (Seddon, 1988).

TABLE V Distance moved from the nest bowl by yellow-eyed penguin chicks during exploratory behaviour in

guard and post-guard phases

Distance from nest bowl (m)

Age Number (days) of chicks Mean (k 1 S.D.) Range

20- 25 26--30 31--35

41-45 46- 50 51- 55 56- 60 61-65 66- 70 71-75 76- 80

36- 40

81-85

91-95 86- 90

96- 100

50 50 50 50 50 50 50 50 48 40 36 36 26 20 12 8

0.1 f 0.3 0.1 f 0.3 0.6k 1.0 1.0f2.1 1.2 +2. I 2.0 2.4 2.0 f 2.5 2.4k2.5 3.7 f 3.9 5.5 & 3.7 6.0 k 4.2 6.6 k4.7 6.8 +4,6 8.9 k 4.9

10.0+5.0 11.8 f 6.5

0- 1 0- 1 0-3 0-10 0-10 0-10 0-10 0-10 0-1 5 2-15 2-20 2-20 2-20 2-20 5-20 5-20

338 P. J . SEDDON

PLATE I . Yellow-eyed penguin chicks. (a) Chick 7 days old, weighing 285 g. Note egg tooth and sparse primary down. (b) Chick 32 days old, weighing 2.5 kg, in a fully upright posture, showing thick secondary down. (c) Chick 77 days old, weighing 4.8 kg, with traces of down remaining on the shoulders and neck. All photos by Yolanda van Heezik.

YELLOW-EYED PENGUIN CHICK BEHAVIOUR 339

Overheating may become a significant problem for yellow-eyed penguin chicks after 21 days; they avoid direct sunlight and pant in hot weather. J. R. E. Taylor (1986) found that in still air the down of chinstrap and gentoo penguin chicks is a better insulator than feathers. The heavy down of the yellow-eyed chick prevents heat loss from all external surfaces but the feet. The feet grow rapidly (van Heezik, 1988) and are available as thermal radiators. Following the increased mobility towards the end of the guard phase, chicks seek shaded sites significantly more on hot days (noon ambient temperatures > 19 "C) than on cool days (noon ambient temperature < 13 "C) (x2 = 13.99, dJ = 1, P < 0.001, N = 137 observations). I have also observed chicks seeking out and standing on marshy ground or in running water when ambient temperatures exceed 20 "C (monthly mean = 16.6 "C).

Feeding

The feeding procedure has been described by Richdale (1957: 41-44). Yellow-eyed penguin parents may initiate feeding in the first few days. Female crested penguins (Eudyptes spp.) also initiate feeding during the first two or three days (Warham, 1975). However, active begging does occur on the first day (Table IV). Begging was found to be the first behaviour manifested by the chicks of the pied flycatcher (Ficedulu hypoleucu), the great tit (Purus major) and the redstart (Phoenicurus phoenicurus) in response to a variety of acoustic cues (Khayutin, 1985). Yellow-eyed penguin chicks have their eyes closed until the third or fourth day. Crested penguin chicks' eyes are not clear until four to six days after hatching (Warham, 1975). The ability of the yellow-eyed penguin chick to solicit food may therefore be mediated by non-visual cues such as temperature changes, or adult nest relief ceremony. Movements by brooding adults which briefly expose chicks less than four days old may stimulate begging (P. J. Seddon, pers. obs.), and when the chicks' eyes open there is a gradual increase in the use of visual stimuli to initiate begging, and movements by the attending adult continue to stimulate begging even when the chicks are no longer covered. Thus after about 10 days begging occurs primarily in conjunction with adult nest relief (Table VI). The frequency of begging decreases during the guard phase as chicks begin to beg more often from the returning adult only (Table 111).

TABLE VI Relationship between chick begging and adult behaviour during guardphase in the yellow-eyedpenguin. Figures are

percentages of observed begging bouts

Days of guard phase

Adult behaviour 1- 10 11-20 21-30 3 1 4 +

Settling/vocalizing 78.8 90.9 92.6 96.3 Quiet resting 21.2 9.1 7.4 3.7

Nest relief 20.6 84.8 66.7 87.1 No nest relief 79.4 15.2 33-3 12.9

Number ofbouts 165 66 27 54

340 P. J . SEDDON

Comfort behaviour

Comfort behaviours are the first types of behaviour seen, and in all cases are similar in form to those of adults. The age at which comfort behaviours were first observed are given in Table IV. The yawn was the first of the comfort movements performed by yellow-eyed penguin chicks, and also the first performed by chicks of the Adtlie penguin (Spurr, 1975; Bekoff, Ainley & Bekoff, 1979). There was some confusion between the yawn and the both-wing-stretch in adult Adtlie penguins (Sladen, 1958; Sapin-Jaloustre, 1960). McKinney (1965) labelled the behaviour a jaw-stretch since there was no marked inhalation, but Ainley (1974) stated that penguins do not have a jaw-stretch. Yawning is a stretching movement associated with rest or arousal. Stretching behaviours increase in complexity from a prone single-wing-stretch after one week to the both-wing-stretch and rapid wing-flap after day 16. All these behaviours occur after a period of inactivity and probably serve to increase circulation in anticipation of activity. The head-shake and sneeze have developed by the end of the second week, both serving to remove foreign matter from the head and bill. By the end of the first week the chicks are able to turn themselves to defecate over the nest edge, finishing these movements with the tail-wag. This keeps the nest interior relatively dry and clean, though the frequency and quantity of chick faeces increase. The first preening movements occur between six and 10 days, coinciding with the development of secondary down. Only nibble-preening (Ainley, 1974) is seen during the guard phase; oil-preening commences when the uropygial gland starts to function some time after 60 days. Billing and nibbling movements (Ainley, 1974) are performed while the chick is down-covered, with combing occurring after the growth of the contour feathers (Plate Ic) from about 50 days on. The amount of time spent preening increases throughout the guard phase. Adtlie penguin chicks show an increase in the frequency of preening of areas where down is being lost (Bekoff et al., 1979). After 21 days the yellow-eyed penguin chick begins to preen both the attending parent and later its sibling. This allopreening is performed by Adtlie penguin chicks (Spurr, 1975) but is not part of the adults rtpertoire (Ainley, 1974). Allopreening continues to be performed by adult yellow-eyed penguins and is a major feature of courtship and pair- bonding. Adult allopreening is seen in a number of penguin species (review by Ainley, 1974).

Aggression

Siblings remain together throughout the guard phase, and tend to be found in the same area until fledgling. Stick-biting seen at about eight days is reminiscent of the gripping of bills seen during sibling fights and appears to be the first potentially aggressive use of the bill. A harsh call in response to human disturbance is heard from the 1 1 th day; this call is later heard during agonistic interactions. Overt aggression between siblings occurs from about the third week, at first consisting of bill-gripping and pecking, but developing to flipper-striking and threat postures such as the point. Sibling aggression occurs in three contexts (Table VII): (1) spontaneously-where the victim of an attack has made no approach to the attacker, aggressive or otherwise, and is often resting in a prone posture at the time of the attack; (2) due to individual distance infringements- during exploratory or preening behaviour by one or both chicks the head or flipper of one chick may come suddenly within 5 cm of its sibling, which responds with pecking or flipper-striking; and (3) occasionally during feeding.

In birds which feed their young, sibling competition is often intense (Werschkul & Jackson, 1979). Spurr (1975) stated that Adtlie penguin siblings do not fight for food, but when both are

YELLOW-EYED PENGUIN CHICK BEHAVIOUR

TABLE VII Context of 55 observedaggressive mieractions between yellow-eyedpmguin

chick siblings during the guard phase

34 1

Context -~

Individual Aggression by Spontaneous distance Feeding

One sibling 15 12 3 Two siblings 3 19 3

Total 18 31 6

together they may interfere with each other's feeding. Hatching asynchrony means that first- hatched chicks of Adklie (R. H. Taylor & Roberts, 1962), Galapagos (Boersma, 1976) and jackass penguins (Williams & Cooper, 1984) tend to be larger and heavier than their later-hatched sibs and better able to compete for food, and will maintain this size advantage. The first egg of a yellow- eyed penguin clutch is not incubated efficiently (Seddon, In prep.); this delay in the onset of prone incubation means that chick hatching is synchronous (Richdale, 1957) and in general there is little difference in the size of sibs throughout the dependent phase (van Heezik, 1988). Yellow-eyed penguin chick conflict occurs least during feeding ( x 2 = 17.0, d.J = 2, P e 0.001) and both chicks are usually fed at each session. The lack of mechanisms for brood reduction suggests that the food supply during the chick phase is normally predictable and reliable.

The creching of post-guard phase chicks occurs in a number of penguin species (reviewed in Davis, 1982). Davis (1982) defined a creche as a minimum of three chicks in close association. Yellow-eyed penguin chicks occasionally form groups of three to five following the abandonment of the nest site in the post-guard phase. Such aggregations only occur where two or three nests are in close proximity, or when chicks gather in open loafing areas as part of the general movement seawards. Huddling of unrelated chicks is not seen, and as very cold conditions do not occur, it is unlikely that such grouping functions reduce heat loss. Predation of post-guard phase chicks is rare; they have no aerial predators, and only dogs are capable of killing chicks older than 50 days, so protection from predation seems not to be the function of grouping. It is likely that the use of common access paths through the dense vegetation surrounding nests and the use of loafing sites near landing points bring chicks together. A degree of individual spacing, 0.5-1.0 m, is always evident, and pecks may be directed towards non-siblings if such spacing is violated.

Paren t-ch ick recognition

Yellow-eyed penguins feed only their own chicks, and chicks beg only from their parents. During the guard phase, feeding activity is centred around the nest bowl. Long distances between nests and the visual isolation of most nest sites mean that chicks at this time have virtually no contact with adults other than their parents. Movement away from the nest and the occasional grouping of chicks in the post-guard phase requires that parents should be able to recognize

342 P. J . S E D D O N

offspring and vice versa. A variety of visual and vocal cues are available to mediate this recognition. Parent-chick recognition has been reported for little blue, Eudyptulu minor (Richdale, 1951), rockhopper, Eudyptes chrysocome (Pettingill, 1960; Warham, 1963), royal Eudyptes chrysolophus schlegeli (Warham, 197 I), emperor, Aptenodytes forsteri (Prtvost, 1959, king, Aptenodytes patagonicus (Stonehouse, 1960), chinstrap, Pygoscelis antarcticu (Sladen, 1955), and Adtlie penguins (Sladen, 1953, 1955; Penney, 1968; Thomson & Emlen, 1968; Spurr, 1975).

Five stages of avian behavioural development were recognized by Nice (1 962):

I Post-embryonic: coordinations concerned with nutrition. I1 Preliminary: beginnings of comfort movements.

TIT Transition: escape reactions; comfort movement maturation. IV Locomotory: leaving nest; start of self-feeding. V Socialization: aggression; perfection of locomotion.

Yellow-eyed penguin chicks appear to conform to the same pattern of development as other birds. Phases I and I1 are passed in the first 10 days, with phase 111 occurring between 10 and 20 days. Locomotory ability and exploratory behaviour increase, and aggression is seen after 2 1 days. Unlike the Adtlie penguin chicks (Spurr, 1979, yellow-eyed chicks do not perform any of the adult vocal displays before fledging. Sexual behaviour does not fully develop for at least two years, with some females first breeding at two years of age, and some males breeding at three years (Richdale, 1957).

Summary

Yellow-eyed penguin chicks were observed at marked nests from the time of hatching to the beginning of the post-guard phase. The chicks are semi-altricial at hatching, and are brooded for the first 25 days. As with the Adklie penguin chick (Spurr, 1975), feeding and comfort behaviours are the first to develop, followed by locomotion and aggressive behaviour. This follows the order of development determined by Nice (1 962) for several species of birds. After about 2 1 days chicks may become overheated at exposed nest sites, panting and avoiding direct sunlight. The guard phase lasts for about 45 days, after which the chicks are without adult protection during the day. Long distances between nests prevent large chick cr6ches from forming. Sibling rivalry is not intense and usually both chicks are fed at each feeding session. Fledging and complete independence occur at about 15 weeks.

For assistance in the field I am grateful to J. S. Burgess, R. J. Seddon, B. Speirs and M. Edwards. J. T. Darby, L. S. Davis, D. Boersma, J . Warham and Y. van Heezik gave useful advice and comments. I thank J . Braid for granting access to his land, and Mrs F. Stone for letting me use the Boulder Beach cottage. Financial support came from the Otago Peninsula Trust, the Royal Forest and Bird Protection Society Inc., and from an Otago University Research Scholarship and an Internal Affairs Wildlife Service Scholarship.

REFERENCES

Ainley, D. G. (1974). The comfort behaviour of Ad& and other penguins. Eehauiour 5 0 16-51. Altmann, J. (1974). Observational study of behaviour: sampling methods. Eehauiour 4 9 227-267. Anokhin, P. K. (1964). Systemogenesis as a general regulator of brain development. Prog. Erain Res. 9 54-76. Bekoff, M., Ainley, D. G. & Bekoff, A. (1979). The ontogeny and organization of comfort behavior in Adelie penguins.

Boersma, P. D. (1976). An ecological and behavioural study of the Galapagos penguin. Living Bird 15 43-93. Wilson Bull. 91: 255-270.

YELLOW-EYED PENGUIN CHICK BEHAVIOUR 343

Davis, L. S. (1982). Creching behaviour of Adklie penguin chicks (Pygoscelis adeliae). N.Z. JI Zool. 9: 279-286. Khayutin, S. N. (1985). Sensory factors in the behavioural ontogeny of altricial birds. Adv. Study Behau. 1 5 105-152. McKinney, F. (1965). The comfort movements of Anatidae. Behaviour 2 5 120-220. Nice, M. M. (1962). Development of behavior in precocial birds. Trans. Linn. Soc. N.Y. H: 1-21 1 . Penney, R. L. (1968). Territorial and social behavior in the Adelie penguin. Antarctic Res. Ser. Washington 12: 83-131. Pettingill, 0. S. (1960). Creche behavior and individual recognition in a colony of Rockhopper Penguins. Wilson Bull. 7 2

Prkvost, J. (1955). Observations tcologiques sur le Manchot Empereur (Aptenodytesforsteri). Int. orn. Congr. 11: 248-251. Richdale, L. E. (1951). Sexual behavior in penguins. Lawrence: Univ. Kansas Press. Richdale, L. E. (1957). A population study of penguins. Oxford: Clarendon Press. Sapin-Jaloustre, J. (1960). Ecologie du Manchot Adilie. Paris: Hermann. Seddon, P. J. (1988). Patterns of behaviour andnest site selection in the Yellow-eyed Penguin (Megadyptes antipodes). PhD

Sladen, W. J. L. (1953). The Adtlie penguin. Nature, Lond. 171: 952-955. Sladen, W. J. L. (1955). Some aspects of the behaviour of Adelie and Chinstrap Penguins. Int. orn Congr. 11: 241-247. Sladen, W. J. L. (1958). The pygoscelid penguins. I. Methods of study. 11. The AdClie penguin Pygoscelis adeliae (Hombron

& Jacquinot). Scient. Rep. Falk Isl. Depend. Sum. No. 17: 1-97. Spurr, E. B. (1975). Behavior of the Adklie penguin chick. Condor 77: 272-280. Stonehouse, B. (1960). The King Penguin Aptenodytes patagonica of South Georgia. I. Breeding behaviour and

development. Scient. Rep. Falkld Isl. Depend. Surv. No. 23: 1-81. Taylor, J. R. E. (1985). Ontogeny of thermoregulation and energy metabolism in pygoscelid penguin chicks. J . romp.

Physiol. (B) 155 61 5-627. Taylor, J. R. E. (1986). Thermal insulation of thedown and feathersofpygoscelid penguin chicksand the unique properties

of penguin feathers. Auk 103: 160-168. Taylor, R. H. & Roberts, H. S. (1962). Growth of the Adelie penguin (Pygoscelis adeliae Hombron & Jacquinot) chicks.

N.Z. JI Sci. 5: 191-197. Thomson, D. H. & Emlen, J. T. (1968). Parent-chick individual recognition in the Adelie Penguin. Antarctic JI U S . 3: 132. van Heezik, Y. (1988). The growth and diet of the Yelloweyed Penguin, Megadyptes antipodes. PhD thesis, University of

Warham, J. (1963). The Rockhopper penguin, Eudypres chrysocome, at Macquarie Island. Auk 80: 229-256. Warham, J. ( I 971). Aspects of breeding behaviour in the royal penguin Eudyptes chrysolophus sehlegeli. Notornis 18: 91-

Warham, J. (1975). The crested penguins. In The biology ofpenguins: 189-269. Stonehouse, B. (Ed.). London: Macmillan. Werschkul, D. F. & Jackson, J. A. (1979). Sibling competition and avian growth rates. Ibis 121: 97-102. Williams, A. J. &Cooper, J. (1984). Aspects of the breeding biology of the jackass penguin Spheniscus demersus. Proc. pan-

21 3-22 1.

thesis, University of Otago, Dunedin.

Otago, Dunedin.

115.

Afr. orn. Congr. 5 841-853.