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Showing papers in "The Auk in 1984"


Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: A review of the methods used to study seabirds at sea from ships can be found in this article, where the authors discuss the problems posed in making reliable observations in relation to the design of research programs and describe a method currently in use around the seas of Great Britain.
Abstract: --We review the methods used to study seabirds at sea from ships, discuss the problems posed in making reliable observations in relation to the design of research programs, and describe a method currently in use around the seas of Great Britain. We suggest a framework for future studies, incorporating features likely to stabilize bias. The key items in this recommendation are (1) the use of a band transect in order to provide density estimates, and (2) a method to correct for movement of flying birds in the band transect in order to minimize bias caused by such movement. Received 13 October 1982, accepted 5 December 1983. THE recent upsurge in studies of seabirds at sea has often been in response to the need to assess the potential impact of hydrocarbon developments offshore. Marine biologists are also realizing that seabirds play an important part in marine ecosystems, and seabird ornithologists are becoming aware of the fact that studies of seabird biology must extend beyond the colonies. Attempts to produce systematic ounts of seabirds at sea have resulted in almost as many methods as there have been studies. In this paper, we review these methods and discuss associated problems. If studies are to become more comparable, the methods used will have to become more standardized; therefore, we suggest an approach that may help achieve this aim. DEVELOPMENT OF QUANTITATIVE SURVEYS

627 citations


Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: The results support the view that intraclutch variation in egg size has an ultimate, adaptive value and suggest that birds adopting the "brood-reduction strategy" have a small final egg, particularly those birds with large clutches, whereas birds adopted the " Brood-survival strategy" has a relatively large final egg.
Abstract: -Using data from the field and the literature on 67 species of birds, we analyzed intraclutch variation in egg size, especially the deviation of the last egg from the clutch mean (D). Values of D are closer to zero in precocial than in altricial species; D is negatively correlated with body size in interspecific comparisons, i.e. large birds, including precocial species, lay small final eggs; and D is higher in open-nesting passerines (on average D = +3.56%, 17 species) than in hole-nesting species (on average D = -0.05%, 13 species). Within populations of birds, a negative relationship exists between D and clutch size, particularly in species that have a generally low value of D. The results support the view that intraclutch variation in egg size has an ultimate, adaptive value. We suggest that birds adopting the "brood-reduction strategy" have a small final egg, particularly those birds with large clutches, whereas birds adopting the "brood-survival strategy" have a relatively large final egg, particularly those birds with large clutches. Received 5 December 1983, accepted 19 April 1984. BIRDS possess several mechanisms by which they can adjust the magnitude and pattern of their breeding effort in relation to environmental conditions and to their own breeding condition. The most important of these factors is clutch size (Lack 1954, O'Connor 1978, Lundberg and Vaisanen 1979). Other proposed mechanisms are the sex ratio of the brood (Trivers and Willard 1973, Howe 1976, Fiala 1981), egg quality (Schifferli 1973, Howe 1978, Ricklefs et al. 1978, O'Connor 1979, H6gstedt 1981, Birkhead and Nettleship 1982), hatching pattern (Lack 1954, Ricklefs 1965), and intraclutch egg-size variation (Parsons 1970, 1976; Howe 1976; Ryden 1978; Ojanen et al. 1981). When clutch-size adjustments and the influence of nest predation are excluded, a pronounced variation still is found among birds in the proportion of eggs that are successful. The hatchability of the eggs (Koenig 1982) and nestling mortality vary significantly. In many passerine birds, for example, nestling mortality from starvation is rather low (Nice 1957, Ricklefs 1969, Slagsvold 1982a), compared with that of some birds of prey in which one of the two young in the brood always dies (Stinson 1979, Edwards and Collopy 1983). It has been assumed that birds that lay relatively many eggs in relation to the number of young that they are normally able to feed (e.g. raptors) have adopted a brood-reduction strategy that enables them to adjust the number of offspring they rear in relation to the environmental conditions that prevail during the nestling stage. This is brought about by hatching asynchrony, a phenomenon that results in a size hierarchy within the brood (Lack 1954, Ricklefs 1965, Hahn 1981, Slagsvold 1982a). Clark and Wilson (1981), however, cited data on the hatching patterns of several species of altricial birds and claimed that, rather than supporting the broodreduction hypothesis, these data supported predictions adduced from a model based on the probabilities of nest failures occurring. In many species of passerine birds egg size increases with laying order, and this phenomenon is indeed difficult to explain by means of the broodreduction hypothesis (Clark and Wilson 1981). In the present paper, we report the results of an interand intraspecific comparison made with regard to such within-clutch egg-size variation. A large body of data now exists for a wide variety of bird species, and the time is ripe for a comparative analysis. The patterns of such egg-size variation seem fundamental to an understanding of overall reproductive strategies in birds.

327 citations


Journal ArticleDOI
01 Jan 1984-The Auk
TL;DR: No microgeographic variation of wild songs, no evidence of learning from a tutor tape, nor any similarity of song characters among kin are found, and the vocal development of these suboscine flycatchers is strikingly different from that of typical oscines, where vocal learning is the rule.
Abstract: -I studied the song development of five Willow Flycatchers (Empidonax traillii) and four Alder Flycatchers (Empidonax alnorum) taken from nests at 7-10 days of age. Three Willow Flycatchers and four Alder Flycatchers were tutored with songs of the other species, and two Willow Flycatchers served as controls, hearing only conspecific songs. All nine subjects, both females (when administered exogenous testosterone) and males, and both experimentals and controls, produced remarkably normal songs; slight differences between songs of wild and experimental subjects could be attributed to motivational states rather than to the effects of acoustic isolation in the laboratory. I found no microgeographic variation of wild songs, no evidence of learning from a tutor tape, nor any similarity of song characters among kin. The vocal development of these suboscine flycatchers is strikingly different from that of typical oscines, where vocal learning is the rule. Received 17 January 1983, accepted 1

236 citations


Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: On etudie le comportement alimentaire de Vireo olivaceus, Setophaga ruticilla, V. philadelphicus, Dendroica caerulescens en fonction des types of plantes et des diverses strates de la foret (New Hampshire).
Abstract: On etudie le comportement alimentaire de Vireo olivaceus, Setophaga ruticilla, V. philadelphicus, Dendroica caerulescens en fonction des types de plantes et des diverses strates de la foret (New Hampshire)

236 citations


Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: Data suggest strongly that the nature of avian mating systems is regulated proximately by temporal patterns of hormone secretion, and that, in monogamous males, plasma T is elevated only early in the season when territories and pair bonds are established, whereas, in polygynous forms, plasma levels of T are elevated for longer periods that may overlap the parental phase.
Abstract: -Recent investigations of the plasma profiles of testosterone (T) in free-living birds suggest that circulating levels of T during the reproductive cycle remain elevated longer in males of polygynous species than in males of monogamous species. When the hormonal profile of polygynous males is mimicked by the administration of subcutaneous implants of T to males of monogamous species, thus maintaining plasma levels of this androgen at high vernal levels, frequencies of territorial aggression and courtship behavior remain elevated, resulting in a marked increase in the size of the territory. A substantial number of T-implanted males also become polygynous, attracting two and sometimes three females to settle on their enlarged territories. These data suggest strongly that the nature of avian mating systems is regulated proximately by temporal patterns of hormone secretion. Received 2 December 1983, accepted 27 April 1984. IN the early spring, males of many passerine birds establish breeding territories to which they then attract a mate or mates. The seasonal development of behaviors associated with the establishment of a territory, courtship, and mate-guarding are regulated by the steroid hormone testosterone (T) (e.g. Hutchison 1978, Farner and Follett 1979, Wingfield and Farner 1980a, Adkins-Regan 1981, Moore 1984). Circulating levels of T in males are elevated throughout the spring, reaching a maximum when females are ovulating and when most copulations occur (Wingfield and Farner 1980a; Wingfield 1980, 1983). In monogamous species there is a rapid decline in plasma levels of T (Wingfield 1980, 1983; Wingfield and Farner 1980a), accompanied by a reduction of territorial and sexual behavior, as soon as the female begins incubation. In polygynous species, however, circulating T remains elevated throughout incubation [e.g. Red-winged Blackbird (Agelaius phoeniceus), W. A. Searcy pers. comm.] or at least until the final mate has begun incubation [e.g. Pied Flycatcher (Ficedula hypoleuca), Silverin and Wingfield 1982]. In the weakly polygynous Western Meadowlark (Sturnella neglecta), plasma levels of T do decline as incubation ensues but then increase for a second time when females are producing a second clutch (Wingfield and Farner 1980b). Monogamous males of captive populations of turtle doves (Streptopelia spp.), however, also manifest an elevation of T during the courtship phases of subsequent broods (Feder et al. 1977). This is unlike most monogamous species, such as the White-crowned Sparrow (Zonotrichia leucophrys; Wingfield and Farner 1978a, b, 1980a), Eurasian Blackbird (Turdus merula; Schwabl et al. 1980), and Song Sparrow (Melospiza melodia; Wingfield 1984a), in which plasma levels of T remain depressed, even though up to four clutches may be produced within a single season. In addition, it has been shown that in the monogamous wild Mallard (Anas platyrhynchos) plasma levels of T decrease as soon as the female is incubating. In domesticated and semidomesticated forms of Mallards, however, the mating system becomes promiscuous, plasma levels of T remaining elevated for longer during the breeding period (Donham 1980, Haase and Donham 1980). Although caution should be exercised in comparing plasma profiles of hormones of truly wild and domesticated forms of the same species, these data do support the hypothesis that, in monogamous males, plasma T is elevated only early in the season when territories and pair bonds are established, whereas, in polygynous forms, plasma T is elevated for longer periods that may overlap the parental phase. This communication reports the effects of mimicking the hormonal profile of polygynous species by administering subcutaneous implants of T to males of monogamous species and thus maintaining plasma levels of this androgen at high springtime levels. MATERIALS AND METHODS Experimental subjects and study sites.-In the spring of 1979, an investigation into the behavioral effects 665 The Auk 101: 665-671. October 1984 This content downloaded from 207.46.13.83 on Fri, 21 Oct 2016 04:47:45 UTC All use subject to http://about.jstor.org/terms 666 JOHN C. WINGFIELD [Auk, Vol. 101 of experimentally altered temporal patterns of T secretion in male White-crowned Sparrows (Zonotrichia leucophrys pugetensis) was initiated at a study site near Hart's Lake, Pierce County, Washington (45?N). Freeliving populations of this race of White-crowned Sparrow are known to be primarily monogamous (Blanchard 1941, Lewis 1975). In the spring of 1981 this experiment was repeated with free-living male Song Sparrows (Melospiza melodia) on the grounds of the Rockefeller University Field Research Center and adjacent lands of the Cary Arboretum of the New York Botanical Society, Millbrook, New York (42?N). Song Sparrows are monogamous, although occasional instances of polygyny are reported (Nice 1943, Smith and Roff 1980). Hormone implants and sampling procedures.-To alter the temporal pattern of circulating T levels, eight territorial male White-crowned Sparrows were given a subcutaneous implant of crystalline T packed into 20-mm lengths of Silastic tubing (internal diameter 1.47 mm, external diameter 1.96 mm; Dow Corning, Midland, Michigan). Controls (n = 9) were given empty implants at a second site some 8 km distant. In the second experiment, a group of 8 territorial male Song Sparrows were given identical implants of T, and in an area 1 km distant a second group of 8 males were given empty implants as controls. All implanted birds were surrounded by untreated but territorial males, and all implants were administered early in spring as territories and pair bonds were being established. Birds were captured in Japanese mist nets or in Potter traps baited with seeds. Blood samples were collected immediately after capture and before implantation. Sparrows were banded with a U.S. Fish and Wildlife Service aluminum band and a unique combination of colored plastic leg bands for identification of individuals during subsequent behavioral observations. All females captured were also color banded. At each capture, body mass was measured to the nearest 0.1 g, fat depot in the furculum and abdomen was assessed on an arbitrary scale, and wing length was recorded to the nearest millimeter. All of these sampling procedures have been described in detail by Wingfield and Farner (1976, 1978a). At intervals throughout the breeding season, experimental birds and controls were recaptured and further samples were collected. Implants were checked at each capture and, in experimentals, T implants were replaced if the original implant was half empty. Behavioral observations.-Birds were identified by color-band combinations during regular censuses at least once a week. The bird's location and interactions with conspecifics were also noted. These observations were divided equally between experimental and control sites. Territory size was measured after boundaries had been established (May-July) as follows: tape-recorded songs of Song Sparrows (territory size was not assessed for implanted Whitecrowned Sparrows) were played to experimental and control males, the position of singing perches was noted on a detailed map, and the area circumscribed by the perches was measured in square meters. Because only singing and display perches were used to identify territory boundaries, these data represent conservative estimates of territory size. Polygynous associations were indicated by the presence of two or more nests within a territory and by repeated observations of breeding females, identified by color bands, associating with a particular male or carrying food to young on an observed male's

213 citations


Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: In this paper, a comparative study of the falconiformes is presented, and the authors discuss des raisons eventuelles tres nombreuses pour expliquer la presence de materiaux verts dans la construction du nid et l'hypothese d'une defense contre les ectoparasites doit etre envisagee avec beaucoup de precautions.
Abstract: Etude comparative pour les falconiformes. Il semble qu'il y ait des raisons eventuelles tres nombreuses pour expliquer la presence de materiaux verts dans la construction du nid et l'hypothese d'une defense contre les ectoparasites doit etre envisagee avec beaucoup de precautions

192 citations


Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: Brant evidently did not use body reserves to obtain nutrients for feather growth during wing molt, which supports the hypothesis thatWing molt is not a nutritional stress for waterfowl.
Abstract: -I collected 150 Brant (Branta bernicla) at East Bay, Southampton Island, Northwest Territories, Canada, in 1979 and 1980 to evaluate how much these birds rely on reserves of fat, protein, and calcium during egg production, incubation, and the subsequent wing molt. Egg laying resulted in decreases in body weight and nutrient reserves of females. These decreases could have accounted for all of the fat but only 70% of the protein in an average clutch. Neither males nor females had sufficient reserves when incubation began to enable them to fast during that period. Only 11% and 22% of the energy required by males and females, respectively, could have been derived from their reserves during incubation. Brant evidently did not use body reserves to obtain nutrients for feather growth during wing molt. Rather, molting males and females accumulated muscle protein, which supports my hypothesis that wing molt is not a nutritional stress for waterfowl. Received 12 August 1983, accepted 29 November 1983. IT is now generally thought that Arctic-nesting geese feed little during egg laying and incubation and that, consequently, stored nutrient reserves are the major determinants of clutch size and the ability of the female goose to complete incubation (Ryder 1970; MacInnes et al. 1974; Ankney 1977a, b; Ankney and MacInnes 1978; Raveling 1979a, b). In order to test my hypothesis that the wing molt is not a nutritional stress in waterfowl (Ankney 1979), I collected male and female Brant (Branta bernicla) on Southampton Island, Northwest Territories, in 1979 during the egghatching period and throughout the subsequent wing molt. To my surprise, both sexes, but particularly females, seemed to be in much better condition at the end of incubation than are Lesser Snow Geese (Chen c. caerulescens). Also, in contrast to Snow Geese (Ankney 1977b), incubating Brant had been feeding before they were collected. Thus, in 1980 I returned to Southampton Island to collect Preand Postlaying Brant, to determine how much these birds rely on nutrient reserves for egg production and during incubation. This paper reports the results of that research and my evaluation of the importance of nutrient reserves to molt-

170 citations


Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: In this article, the methode de double marquage de l'eau is used for the usage of lanius ludovicianus, and les facteurs meteorologiques sont pris en consideration and presentation d'un modele.
Abstract: Utilisation de la methode de double marquage de l'eau. Etude menee chez Lanius ludovicianus; les facteurs meteorologiques sont pris en consideration et presentation d'un modele

151 citations


Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: Etude menee de 1979 a 1983 pres du lac Cranberry, New York : l'insucces d'une premiere nidification avec un partenaire donne dans une localite donnee est une cause determinante de desertion et de dispersion.
Abstract: Etude menee de 1979 a 1983 pres du lac Cranberry, New York. L'insucces d'une premiere nidification avec un partenaire donne dans une localite donnee est une cause determinante de desertion et de dispersion

151 citations


Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: La qualite des aliments sur le site de reproduction peut influencer la dynamique de population des oies en depit de the disponibilite globale elevee des vegetaux herbaces.
Abstract: Observations effectuees dans le delta du Yukon-Kuskokwim Alaska. L'oie beneficie nutritionnellement du choix alimentaire qu'elle effectue. La qualite des aliments sur le site de reproduction peut influencer la dynamique de population des oies en depit de la disponibilite globale elevee des vegetaux herbaces

143 citations


Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: The results were consistent with theoretical models that predict that reproductive effort increases with age or with declining residual reproductive value, and support Williams' (1966) prediction that organisms adapted to living in variable environments adjust their RE in relation to probability of success.
Abstract: -I examined the influence of age and time on female reproductive performance in a marked population of Lesser Scaup (Aythya affinis) breeding in southwestern Manitoba from 1977 to 1980. Arrival date and length of prelaying period varied among years but were not related to female age. Rate of nonbreeding and nest-initiation date varied among years and by female age. Age variation in nonbreeding was due to the failure of yearlings and a few 2-yr-olds to breed. Yearlings began laying an average of 5-8 days later than older females. Clutch size increased with female age but showed no significant annual variation despite extreme changes in water conditions. Reproductive performance generally increased with female age and with improving water conditions. These results were consistent with theoretical models that predict that reproductive effort (RE) increases with age or with declining residual reproductive value. My data support Williams' (1966) prediction that organisms adapted to living in variable environments adjust their RE in relation to probability of success. Female Lesser Scaup exhibited a temporally dynamic reproductive strategy, and natural selection seemingly has favored "yes-if" genes (Williams 1966) that effect breeding only when conditions are favorable for the individual. Received 27 April 1983, accepted 3 October 1983. PARENTAL age and breeding experience influence the reproductive performance of many avian species (Lack 1966, Klomp 1970, Ryder 1980). Among waterfowl, several breeding parameters may vary with age, including spring arrival date, nesting chronology, and clutch size (e.g. Sowls 1955, Finney and Cooke 1978, Krapu and Doty 1979, Baillie and Milne 1982, Rockwell et al. 1983). Reproductive performance of waterfowl also varies annually in response to fluctuating environmental conditions in breeding, wintering, and migration areas (e.g. Crissey 1969, Bengtson 1971, Heitmeyer and Fredrickson 1981, Davies and Cooke 1983, Krapu et al. 1983). Female age and prairie drought are important factors influencing reproduction of Lesser Scaup (Aythya affinis; Rogers 1959, 1964; Trauger 1971). Nonbreeding and age at first breeding in this species have been discussed and speculated upon (see Trauger 1971: 87), but specific factors affecting these breeding parameters re1 Present address: Wetland Wildlife Populations and Research Group, Minnesota Department of Natural Resources, 102 23rd Street, Bemidji, Minnesota 56601 USA. main obscure due to insufficient information on known-age individuals. Trauger (1971) reported that productivity, measured by the proportion of returning marked hens that were later observed with broods, increased with female age from 1 to 4 yr. The consistent low productivity of yearling females was attributed to poor nesting success and nonbreeding (Trauger 1971: 78). I collected reproductive information on a marked population of Lesser Scaup breeding in southwestern Manitoba from 1977 to 1980, a period during which wetland conditions varied dramatically. In this paper, I examine the influence of age and time on the reproductive performance of females. Breeding parameters estimated were: (1) arrival date, (2) rate of nonbreeding, (3) length of prelaying period, (4) nest-initiation date, (5) clutch size, (6) nest success, (7) rate of renesting, and (8) brood survival. Results are discussed in relation to predictions of theoretical models concerning agespecific and temporal variation in reproductive effort. STUDY AREA AND METHODS The 777-ha study area was located 3.3 km southeast of Erickson, Manitoba (50'30'N, 99?55'W) and was de255 The Auk 101: 255-265. April 1984 This content downloaded from 207.46.13.131 on Sat, 15 Oct 2016 04:33:03 UTC All use subject to http://about.jstor.org/terms 256 ALAN D. AFTON [Auk, Vol. 101 TABLE 1. Comparisons of selected environmental parameters and spring arrival dates of Lesser Scaup, 19771980.

Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: Pour trois des sept saisons d'observation, les oiseaux issus de couvee precoces ont un taux plus grand de recrutement que les couvees tardives ou intermediaires entre precocs et tardive.
Abstract: Pour trois des sept saisons d'observation, les oiseaux issus de couvees precoces ont un taux plus grand de recrutement que les couvees tardives ou intermediaires entre precoces et tardives. Pour les autres saisons, pas de differences nettes

Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: Metabolic rate during flight of Sooty Terns was determined to be 4.8 times standard metabolic rate (SMR), much lower than estimates of flight metabolism predicted from previously published equations.
Abstract: --The CO2 production of free-ranging So, oty Terns (Sterna fuscata) was measured using doubly labeled water (HTO-18). Metabolic rate during flight was determined to be 4.8 times standard metabolic rate (SMR). This value is much lower than estimates of flight metabolism predicted from previously published equations. Observations of these birds at sea indicate that flapping flight predominated at the windspeeds (0-5 m/s) that prevailed during our measurement periods, so factors other than gliding must account for the comparatively low flight metabolism we measured. Sooty Tern flight metabolism is similar to that of some other birds, such as swallows and swifts, that also have high aspect ratios and low wing loadings. Received 27 April 1983, accepted 12 October 1983. THE reliability of estimates of energy flow through biotic communities depends upon the extent to which the model used conforms to reality and the accuracy of the input parameters. In a sensitivity analysis of 44 model-specific and species-specific parameters of his bioenergetic model of a seabird colony, Furness (1978) identified several inputs that had the greatest effect on the precision of the model. Among these for Arctic Terns (Sterna paradisaea) were the hours of activity per day, the intercept and exponent of Lasiewski and Dawson's (1967) SMR equation, and the energy requirements of flapping and gliding flight. For birds, such as terns, that spend a large proportion of their foraging time in flight, the accuracy of estimates of daily energy expenditure depends on knowing the total time spent in various flight activities (i.e. flapping, gliding, and hovering) and the metabolic cost of those

Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: Etude de l'abondance des ressources et de leur utilisation par Accipiter striatus et A. cooperii dans de two zones of l'Oregon de 1969 a 1974.
Abstract: Etude de l'abondance des ressources et de leur utilisation par Accipiter striatus et A. cooperii dans deux zones de l'Oregon de 1969 a 1974

Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: Il semble y avoir une tres grande difference dans le temps de retention des parties dures des proies ingerees par les oiseaux marins, les becs d'encornet persistant dans l'estomac beauoup plus long temps que les parties dure des autres proies.
Abstract: Il semble y avoir une tres grande difference dans le temps de retention des parties dures des proies ingerees par les oiseaux marins, les becs d'encornet persistant dans l'estomac beauoup plus long temps que les parties dures des autres proies. Il faut tenir compte de ces faits pour etudier le regime alimentaire de ces oiseaux

Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: The energetics of postnatal growth and development of wild and captive Northern Gannet chicks are described and net growth efficiency was 49% to 8 weeks of age and 33% to fledging at 13 weeks.
Abstract: We describe the energetics of postnatal growth and development of wild and captive Northern Gannet chicks. For 14 chicks 0-9 weeks old, a 24-week immature, and a breeding female, we determined water, lipid, and nonlipid content. During the 13-week nestling period, mass increased over 40-fold. Accumulation of lipid caused the energy density of chicks to increase steadily through 9 weeks. Lipid eventually accounted for about 60% of energy in tissues. Two captive chicks grew at rates comparable to wild young and consumed, on average, about 24 kg of fish containing 190,000 kJ during the nestling period. The energy density of chick guano was 13.3 ± 0.8 kJ/g. Estimated metabolizable energy (ME) rose rapidly from 952 kJ during week 1 to 19,318 kJ during week 6, after which ME fluctuated between about 9,000 and 16,400 kJ/week. During week 1, the growth increment (GI) was 801 kJ; GI increased sharply to 9,667 kJ during week 4 and peaked at 12,711 kJ in week 7. Net growth efficiency was 49% to 8 weeks of age and 33% to fledging at 13 weeks. The food requirement of the gannet population of Newfoundland is estimated.



Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: On tente d'estimer le biais methodologique lie a l'observateur lorsque la densite de population varie as mentioned in this paper, on tente de leur et al.
Abstract: On tente d'estimer le biais methodologique lie a l'observateur lorsque la densite de population varie

Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: Il existe donc une grande plasticite dans un processus generalement considere comme rigide le plus au nord possible mais qui leur permet aussi des deplacements orientes correctement si les conditions deviennent defavorables.
Abstract: Les oiseaux maintiennent un etat physiologique qui leur permet d'hiverner le plus au nord possible mais qui leur permet aussi des deplacements orientes correctement si les conditions deviennent defavorables. Il existe donc une grande plasticite dans un processus generalement considere comme rigide

Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: The division of labor between the sexes of Golden Eagles during breeding is quantified and these activities to the food consumption of nestlings are related to theories of sexual size dimorphism and parental investment.
Abstract: -A field study of Golden Eagles (Aquila chrysaetos) nesting in and near the Snake River Birds of Prey Area was conducted during 1977-1979. Patterns of parental care differed between female and male eagles during incubation and chick rearing; males consistently captured more food throughout all phases of brood rearing (1.2 vs. 0.6 prey/day), while females typically fed and tended the offspring. During the 7th through 9th week of chick rearing, when the food requirements of nestlings were greatest, the female contributed 43% of the prey biomass. No differences were observed in mean daily capture rates between 1978 and 1979 or between parents of one-chick broods and parents of two-chick broods. Although there were no differences between the sexes in the mean weight of prey captured, there were significant differences among pairs, suggesting differences in prey availability or hunting ability. The daily food consumption of eaglets increased as chick rearing progressed and peaked between the 7th and 9th week. Comparisons between eaglets in different-sized broods revealed that individuals in multiple-chick broods received more food from adults than those in one-chick broods. Late in chick rearing, however, those chicks competing with siblings for food had lower consumption rates. Received 24 February 1984, accepted 1 May 1984. THE general nesting biology of Golden Eagles (Aquila chrysaetos) has been described by many naturalists (e.g. MacPherson 1909, Gordon 1927, Bent 1937). Several studies also have been conducted specifically on territory size (Dixon 1937), molt (Jollie 1947), and growth (Sumner 1929, 1933). More recently, research on Golden Eagles has focused on diet and food requirements (e.g. Fevold and Craighead 1958, McGahan 1967, Mollhagen et al. 1972) and nesting success (e.g. Smith and Murphy 1973, U.S.D.I. 1979). Although these studies contributed greatly to our understanding of eagle biology, none has described the relationship between nestling food consumption and parental care. In this paper, I quantify the division of labor between the sexes of Golden Eagles during breeding and relate these activities to the food consumption of nestlings. The size and total biomass of prey delivered to young by male and female eagles also are considered in relation to theories of sexual size dimorphism and parental investment. STUDY AREA AND METHODS The study was conducted along the Snake River Canyon and surrounding upland desert plateau south ' Present address: School of Forest Resources and Conservation, 118 Newins-Ziegler Hall, University of Florida, Gainesville, Florida 32611 USA. of Boise, Idaho. This 195,063-ha area, known as the Snake River Birds of Prey Area (BPA), is administered by the Bureau of Land Management and lies within the Great Basin semidesert scrub biome (Whittaker 1975). The major vegetation types in the area include big sagebrush (Artemisia tridentata) associations, grasses (Poa and Bromus spp.), and shadscale (Atriplex confertifolia). Approximately one-fifth of the BPA is cultivated. A more detailed description of the vegetation can be found in U.S.D.I. (1979) and Collopy (1980). Incubation data were collected in 1977-1979 from 11 nesting attempts. Weekly observations at each site were made from a prominent location 150-750 m from the nest, and the amounts of time each parent spent incubating or brooding were recorded. Instances of male eagles providing prey to females when relieving them from incubation also were recorded. Data during the nestling period were collected at the same four nest sites in 1978 and in 1979. Daylong observations at each study site were made once every 6 days from blinds 15-40 m away. Photographs showing unique plumage characteristics of the breeding adults in 1978 and in 1979 revealed that the same individuals nested at the same sites in both years. The sex of parents was determined from these photographs, from size differences, and from behavior. I identified parents during each nest visit by using these unique plumage characteristics and by comparing photographs of adults taken during each visit. Adults away from the nest were monitored by a second observer, so when identification of the parent on the nest seemed uncertain it was confirmed by accounting for the location and sex of its mate. For a detailed description of nestling diet and nest 753 The Auk 101: 753-760. October 1984 This content downloaded from 157.55.39.247 on Sun, 27 Mar 2016 07:03:43 UTC All use subject to http://about.jstor.org/terms 754 MICHAEL W. COLLOPY [Auk, Vol. 101 observation and visitation procedures see Collopy (1983a). Parental care of nestlings involved both sheltering and feeding. Sheltering activities included brooding and shading, and both are discussed in this paper. Both the delivery of prey to the nest and its consumption by nestlings were considered feeding activities. The parental care of each adult was analyzed in relation to the age of its offspring. Following each observation period, I measured the body weight and foot-pad size (tip of hallux to tip of middle toe on extended foot) of the chicks (Kochert 1972). Determination of the sex of each chick was made late in the nestling period when size dimorphism became obvious. All prey delivered to the nest during each observation period were identified to species and assigned to a size class. The estimated proportion of the carcass delivered and sex of the eagle delivering the prey also were recorded. I calculated prey biomass delivered to nests from the estimate of the proportion of the carcasses delivered and the species' weights (Steenhof 1983). A series of experiments on the food consumption and growth energetics of captive Golden Eagle chicks was conducted concurrently with this study (Collopy 1980). These feeding trials were designed to monitor the consumption rates of eaglets presented blacktailed jackrabbit (Lepus californicus) food ad libitum and to quantify their growth rates. Because of permit restrictions, the birds were tested only between the ages of 11 and 57 days old. Following the experiments, they were returned to foster eagle nests in the wild, from which they all successfully fledged. During the feeding trials, it was apparent that one meal each day was much larger than all others and that it represented the maximum quantity a chick that age could consume. I quantified this relationship for the two female and two male eaglets tested by expressing the maximum meal size (Y, grams) as a function of age (X, days): female: Y = -99.96 + 12.31X; R2= 0.87, P < 0.0001; male: Y = -20.76 + 7.68X; R2= 0.85, P < 0.0001. Following each meal, the percentage of the crop of each wild nestling that was full was estimated, and the amount of food consumed was calculated. Statistical procedures used to analyze data included the Chi-square test, two-sample t-test, and analysis of variance (Remington and Schork 1970). Assumptions of the normality and equal variance of the statistical models were tested; percentage data were arcsine transformed before analysis whenever they were outside the interval between 30 and 70%. All means are reported with standard errors. RESULTS Incubation.-A total of 692 daylight hours (56 observation days) of data was collected at 11 Golden Eagle nests during incubation in 19771979. At the 10 sites that hatched young, female eagles spent a significantly greater portion of the day incubating (82.6 ? 1.6%) than males did (13.8 ? 1.8%) (t = -22.90, P < 0.0001). Eggs were left exposed only 3.7 ? 0.4% of the daylight hours. In addition to performing the majority of the daytime incubation, only females incubated at night. Overall, males relieved incubating females 2.1 ? 0.1 times daily and averaged 49.4 ? 4.7 min per incubation bout. Of the 111 male-initiated changeovers, 17 (15.3%) involved food transfers to the female on or near the nest. Eagle behavior away from the nest was not monitored systematically during incubation; females occasionally were observed foraging on their own, however, when males did not provide them with food. The unsuccessful eagle pair abandoned their nesting effort during the third week of incubation in 1978. The male incubated only once during my 23.4 h of daylight observations and did not deliver any food to his mate. The lower incubation time of the female (67.5% of daylight hours) and the greater exposure time of the eggs (31.6%) suggest that inattentiveness by the male may have forced the female off the nest to forage and ultimately to abandon her effort altogether. No direct evidence exists that the male who successfully bred at this site in 1977 died or was supplanted, but the lack of synchrony between the pair in 1978 suggests that a different male was present. Brooding/shading nestlings.-A total of 1,248 daylight hours (86 observation days) of data was collected during chick rearing at eight nests in 1978-1979. Chick rearing was defined as the period between the hatching of the first egg and the fledging of the last offspring. Although males regularly landed on nests to deliver prey, they were present only 0.6 ? 0.2% of the observation time. I observed a male brooding and feeding nestlings only once during the study. Clearly, the parental role of males during brood rearing was to provide food, because essentially no time was invested in brooding or feeding young. Several other workers who closely monitored parental behavior at the nest also reported that male eagles rarely brooded or fed young (Hunsicker 1972, Hoechlin 1974, Ellis 1979). This content downloaded from 157.55.39.247 on Sun, 27 Mar 2016 07:03:43 UTC All use subject to http://about.jstor.org/terms October 1984] Care and Feeding of Golden Eagles 755

Journal ArticleDOI
Juan Moreno1
01 Oct 1984-The Auk
TL;DR: The hypothesis that a division of labor in altricial birds has evolved to allow parents to locate their young more easily and to reduce travel distances between sites at which prey are captured and the locations of young is supported.
Abstract: -The care of fledged young by parents and the interactions between parents and young were studied in seven broods of Northern Wheatears (Oenanthe oenanthe L.) in an agricultural area near Uppsala, central Sweden. Time budgets of young and the development of foraging skills were also quantified. Young of the same brood were observed out of the nestholes on the 15th or 16th day after hatching. The parents did not divide the brood until day 3 or 4, day 1 being the 16th day after hatching (assuming that all young fledged on the 15th day). Full stability of family units, with no transfers of responsibility for feeding specific young, was achieved on days 3-8. Both parents fed their respective groups of young at different sites, and young of the same family unit appeared to be aggregated in the territories. They perched nearer to each other on average than to young fed by the other parent. These results support the hypothesis that a division of labor in altricial birds has evolved to allow parents to locate their young more easily and to reduce travel distances between sites at which prey are captured and the locations of young. Young wheatears depended on their parents for 2 weeks after leaving the nest. During that time, they became more active and mobile, spent less time calling and waiting for the parents to feed them, chased their parents more intensively to obtain food, and spent more time foraging. The marked increase in the chasing frequency of young after the first week coincided with a marked decrease in parental feeding rates and in the responsiveness of the parents to the begging calls of the young. Young also greatly increased their foraging activity after day 10, when parental feeding rates dropped to very low levels. These data support the hypothesis that parental reluctance to feed the young determines the onset of fledgling independence. Rates at which young attempted to capture prey and the proportion of successful attacks increased with age. Foraging techniques that are more dependent on flight performance (aerial hawking, perch-to-ground sallying) appeared later and were used less by the young than was ground-gleaning. There was a negative relationship between the intensity of chasing by the young and their capture success rates during different hours, which suggests that they switched between chasing the parents and self-feeding, depending on which was the most profitable strategy at the moment. Received 4 November 1983, accepted 12 April 1984. PARENTAL care in altricial birds has been studied mainly during the nestling period, as it is often difficult to observe young after they have left the nest. In most passerine birds, however, parental care continues after the young leave the nest. The length of this period varies in different species and can be twice as long as the period of feeding nestlings (Skutch 1976). Few quantitative studies have dealt with parental feeding of fledglings (but see Davies 1976, Smith 1978, Smith and Merkt 1980), although parental investment after the young leave the nest has been suggested to be even greater than during the nestling stage (Royama 1966, Drent and Daan 1980). A division of labor between the parents when feeding fledged young, each parent feeding only certain individuals of the brood, has been reported in several studies of passerines (Snow 1958, Nolan 1978, Smith 1978). Smith (1978) suggested that labor division would be an advantage in that it would help the parents to locate young and would lead to a reduction in parental travel times and, therefore, in energy expenditure. For this advantage to occur, the division of labor should be accompanied by the spatial separation of the two groups of young in different parts of the territory. In this field study of Northern Wheatears (Oenanthe oenanthe L.) feeding fledged young, I have looked at 741 The Auk 101: 741-752. October 1984 This content downloaded from 157.55.39.208 on Fri, 29 Jul 2016 06:08:23 UTC All use subject to http://about.jstor.org/terms 742 JUAN MORENO [Auk, Vol. 101 the location of young in the territories and at the distribution of parental feedings among dif-

Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: The maximum daily energy expenditure for females was about four times predicted BMR, similar to values reported in other studies, and water-turnover rates paralleled CO2 production over the nesting cycle, the average values for each sample varying between 0.048 and 0.070 per h.
Abstract: -We measured rates of carbon-dioxide production and water turnover in adult starlings by the doubly-labeled water technique. CO2 production of females was 4.23 cm3g-l h-1 during the incubation period, 4.86 cm3 g-' h-I during the early part of the nestling period, and 6.86 cm3 g-1 h-I during the middle of the nestling period, the time of greatest food requirement by the brood. During the last period, the rate of CO2 production by males was 5.50 cm3 gh-1. CO2 production was independent of brood size (3-7, approximately a two-fold range of brood mass) during both the early and middle parts of the nestling period. Water-turnover rates paralleled CO2 production over the nesting cycle, the average values for each sample varying between 0.048 and 0.070 per h. Within each of the samples, waterturnover rates were independent of CO2 production but appeared to be influenced by weather conditions. During the middle of the nestling period, water-turnover rates were higher on 2 cold, rainy days than on 2 milder days. The maximum daily energy expenditure for females was about four times predicted BMR, similar to values reported in other studies. Received 19 August 1983, accepted 4 March 1984. DAILY energy expenditure (DEE) of adult birds has been the subject of many recent studies (Walsberg 1977, 1978, 1983; Mugaas and King 1981). A few investigators have attempted to relate DEE to variations in the time and energy demands of activities during the nesting cycle and to conditions of the environment. For example, Drent and Daan (1980) concluded that the maximum daily work capacity of birds during the nesting cycle is about four times the basal metabolic rate. Some investigators, using time and energy budget methods, have suggested that there is an increase in DEE between the incubation and nestling periods (Walsberg 1977, Mugaas and King 1981); others have found none (Custer 1974, Withers 1977, Holmes et al. 1979, Ettinger and King 1980). Part of this discrepancy may arise from uncertainty over factors converting activity to energy expendi-

Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: Le facteur thermique est le facteur le plus important controlant l'activite de Callipepla gambelii dans le desert du Colorado.
Abstract: Le facteur thermique est le facteur le plus important controlant l'activite de Callipepla gambelii dans le desert du Colorado

Journal ArticleDOI
01 Jul 1984-The Auk
TL;DR: Il existe chez Larus glaucescens un rapport etroit entre la nourriture disponible and le succes reproducteur.
Abstract: Il existe chez Larus glaucescens un rapport etroit entre la nourriture disponible et le succes reproducteur

Journal ArticleDOI
01 Oct 1984-The Auk
TL;DR: For example, the authors found that red-winged blackbirds (Agelaius phoeniceus) can acquire food preferences and aversions by observing conspecifics.
Abstract: -Red-winged Blackbirds (Agelaius phoeniceus) can acquire food preferences and aversions merely by observing conspecifics. In Experiment 1, red-wings were trained to prefer or avoid food paired with yellow, as conspecifics watched. After training, all birds were given two-choice tests between food paired with yellow or green for 12 days. Trainers were tested in visual isolation, whereas watchers were tested either in visual isolation or in visual contact with birds who had observed the opposite behavior during training. Food aversions were more resistant to extinction than food preferences (P < 0.05), and, among watchers, social cues facilitated avoidance (P < 0.05). In Experiment 2, red-wings were trained to avoid food paired with yellow, as Common Grackles (Quiscalus quiscula) and red-wings watched, or vice versa, and then two-choice tests were given between yellow and green. Both grackles and red-wings exhibited observational learning, regardless of the training species (P's < 0.05). Social interactions among avian predators may influence how predator abundance affects the Batesian model-mimic complex. We speculate that avoidance learning, which occurs when a predator observes the ingestion of a model, is stronger than preference learning, which occurs when a mimic is ingested. Relatively few models would be needed for the model-mimic complex to operate successfully, and the number of mimics could exceed the number of models without jeopardizing the mimetic advantage. Received 4 November 1983, accepted 12 March 1984. RED-WINGED Blackbirds (Agelaius phoeniceus) can learn food preferences and aversions by observing conspecifics feed and without necessarily ingesting food themselves (Mason and Reidinger 1981, 1982a). Such observational learning is guided by the visual characteristics of the food (Mason and Reidinger 1983a), although tactile and gustatory stimuli, as well as the long-term consequences of ingestion, may become important. Such findings are consistent with results obtained from other species (Klopfer 1959, Duecker 1976). Regarding preferences, Common Chaffinches (Fringilla coelebs), for example, are more likely to commence feeding and to sample new foods when exposed to conspecifics doing so (Rubenstein et al. 1977). White Wagtails (Motacilla alba) and Tennessee Warblers (Vermivora peregrina) behave in a similar fashion (Davies 1976, Tramer and Kemp 1979), and European Starlings (Sturnus vulgaris) may increase feed' The third author is assigned to the Monell Chemical Senses Center from the U.S. Fish and Wildlife Service, Denver Wildlife Research Center, Section of Supporting Sciences, Building 16, Federal Center, Lakewood, Colorado 80225 USA. ing efficiency while minimizing energy expenditure through social feeding (Hamilton and Gilbert 1969). This social feeding is discriminative, and individuals in the flock tend to choose foods that other birds in the flock are choosing (Murton 1974, Williamson and Grey 1975). Regarding aversions, many insectivorous species learn to avoid visual stimuli associated with prey whose ingestion has sickened them (e.g. Brower 1958a, b, c; Duncan and Sheppard 1965; Wickler 1968; Morell and Turner 1970; Rettenmeyer 1970). Some investigators have suggested that observational avoidance learning may also have implications for Batesian mimicry (e.g. Alcock 1969a, b), a phenomenon in which predators learn to avoid noxious prey by developing conditioned aversions (Mason et al. 1982) and generalize this learning to mimics of the unpalatable items. One such implication is that predator pressure on prey, at least in some instances, may not increase linearly with the number of predators. Instead, social interactions among predators may ultimately determine how predator abundance affects the Batesian complex (Avery 1983). An unanswered question relevant to this issue is 796 The Auk 101: 796-803. October 1984 This content downloaded from 157.55.39.163 on Wed, 21 Sep 2016 05:51:28 UTC All use subject to http://about.jstor.org/terms October 1984] Blackbird Observational Learning 797 the strength (i.e. resistance to extinction) of observationally learned aversions in comparison with similarly acquired preferences. Avian predators are likely to observe attacks by conspecifics on both models and mimics, and, in some cases, observed attacks on mimics should exceed observed attacks on models, because mimics are more numerous (Brower 1960). In the former case, the observer should learn approach, or preference, but, in the latter instance, learned avoidance, or aversion, should accrue. In Experiment 1, we assessed which sort of observational experience would exert greater control over behavior.

Journal ArticleDOI
01 Jan 1984-The Auk
TL;DR: Repartition, regime et comportement alimentaires, cycle reproduction, site de reproduction, incubation, empennage, declin et disparition (1844)
Abstract: Repartition, regime et comportement alimentaires, cycle reproduction, site de reproduction, incubation, empennage, declin et disparition (1844)

Journal ArticleDOI
01 Jan 1984-The Auk
TL;DR: An evaluation of the dynamics of gut morphology in Wood Duck (Aix sponsa) hens provides an opportunity to assess the significance of the changes observed in the size of the digestive organs of Wood Ducks in relation to food habits, diet quality, and reproductive state.
Abstract: -Changes in Wood Duck (Aix sponsa) digestive organs reflect adaptations to accommodate changes in diet quality, metabolism, and food intake. The size of the gizzard, intestine, ceca, and liver of males decreased between fall and spring and correlated with a reduction in the fiber content of the diet. The mean size of the intestine, liver, and ceca of hens increased in response to high dietary fiber in fall and hyperphagia during laying. Decreases in the size of digestive organs in hens were associated with reduced feeding during incubation and decreased dietary fiber between fall courtship and prebreeding. Received 1 April 1983, accepted 8 July 1983. CHANGES in the intestinal morphology of gallinaceous birds have been studied extensively (Leopold 1953, Breitenbach and Meyer 1959, Breitenbach et al. 1963, Anderson 1972, Moss 1972, Pendergast and Boag 1973), but these changes in waterfowl have received less attention. Data that are available for waterfowl indicate that changes in the size of digestive organs can be induced by diet changes in penned birds (Miller 1975) and also occur under freeliving conditions in both breeding (Korschgen 1976, Ankney 1977) and wintering (Paulus 1982) birds. The size of digestive organs in American Eiders (Somateria mollissima dresseri) (Korschgen 1976) and Lesser Snow Geese (Chen caerulescens caerulescens) (Ankney 1977) declines substantially during laying and incubation. Both species reduce feeding activity during these stages of the reproductive cycle, and, therefore, decreases in the size of their digestive organs have been attributed to reduced food intake I Contribution from Gaylord Memorial Laboratory (School of Forestry, Fisheries, and Wildlife, University of Missouri-Columbia and Missouri Department of Conservation cooperating), Division of Wildlife Refuges, U.S. Fish and Wildlife Service, and Missouri Agricultural Experiment Station Project 170, Journal Series Number 8-154 and the School of Natural Resources, University of Michigan-Ann Arbor. 2 Present address: Center for Environmental and Estuarine Studies, Appalachian Environmental Laboratory, University of Maryland, Frostburg, Maryland 21532 USA. and/or to the mobilization of protein for reproduction. In contrast, Wood Duck (Aix sponsa) hens feed throughout laying and incubation and exhibit marked changes in diet during the reproductive cycle (Drobney and Fredrickson 1979). Therefore, an evaluation of the dynamics of gut morphology in this species provides an opportunity to assess the significance of the changes observed in the size of the digestive organs of Wood Ducks in relation to food habits, diet quality, and reproductive state.

Journal ArticleDOI
01 Apr 1984-The Auk
TL;DR: In this article, the Cayenne Tern and the Yellow-billed Tern were identified as a breeding species of the Sterna eurygnatha (Thalasseus maximima maxima).
Abstract: & K. H. Voous. 1960. The breeding of the Cayenne Tern or Yellow-billed Tern in Cura,ao in 1958. Ardea 48: 51-65. BOND, J. 1956. Check-list of birds of the West Indies (plus Supplements 1-24, 1956-1982). Philadelphia, Academy of Natural Sciences. BUCKLEY, F. G., & P. A. BUCKLEY. 1972. The breeding ecology of Royal Terns Sterna (Thalasseus) maxima maxima. Ibis 114: 344-359. , & . In press. Social behavior of Royal Terns. In Handbook of the birds of Europe, the Middle East and North Africa: the birds of the western Palearctic, vol. 4 (S. Cramp et al., Eds.). Oxford, Oxford Univ. Press. BUCKLEY, P. A., & F. G. BUCKLEY. 1970. Notes on the distribution of some Puerto Rican Birds, and on the courtship behavior of White-tailed Tropicbirds. Condor 72: 483-486. DACIUK, J. 1976. Notas faunisticas y bioecologicas de peninsula Valdes y Patagonia. XVII. Colonias de nidificacion de Egretta alba egretta (Gmelin) y Sterna eurygnatha Saunders recientemente encontradas en las coastas de Chubut (Rep. Argentina). Physis 35: 341-347. ESCALANTE, R. 1970. Notes on the Cayenne Tern in Uruguay. Condor 72: 89-94. . 1973. The Cayenne Tern in Brazil. Condor 75: 470-472. . In press. The Royal Tern as a breeder and migrant on the Atlantic Coast of South America. In Neotropical ornithology (P. A. Buckley et al., Eds.). Ornithol. Monogr. JUNGE, G. C. A., & K. H. Voous. 1955. The distribution and relationship of Sterna eurygnatha Saunders. Ardea 43: 226-247. KEPLER, C. B., & A. K. KEPLER. 1977. The seabirds of Culebra and its adjacent islands, Puerto Rico. Living Bird 16: 21-50. NORTON, R. 1982. West Indies Region, nesting season 1982. Amer. Birds 36: 1019-1020. SICK, H., & A. P. A. LEAo. 1965. Breeding sites of Sterna eurygnatha and other seabirds off the Brazilian coast. Auk 82: 507-508. Voous, K. H. 1968. Geographical variation in the Cayenne Tern. Ardea 56: 184-187. 1983. Birds of the Netherlands Antilles, second ed. Zutphen, Netherlands, De Walburg Pers.