Seasonal differences in the hormonal control of territorial aggression in free-living European stonechats

In birds, territorial aggression during the breeding season is regulated by testosterone (T). However, many bird species also express aggressive behavior during the nonbreeding season, when plasma levels of T are low. It has been suggested that during this period estrogens might play a major role in regulating territorial aggression. In the present study we compared the effects of simultaneous blockage of androgenic and estrogenic actions on territorial aggression during the breeding and nonbreeding seasons in free-living male European stonechats (Saxicola torquata rubicola). European stonechats are of particular interest since they establish territories and form pairs during both the breeding and the nonbreeding seasons. Thus territorial aggression and its endocrine control can be compared between reproductive and non-reproductive contexts. Inhibition of androgenic and estrogenic actions by simultaneous application of Flutamide and ATD reduced territorial aggression during the breeding season, but not during the nonbreeding season. Our results show that androgens and/or estrogens are involved in the endocrine control of territorial aggression in stonechats only in a reproductive context, but not in a non-reproductive one.     

Non-migratory stonechats show seasonal changes in the hormonal regulation of non-seasonal territorial aggression

In many birds and mammals, male territorial aggression is modulated by elevated circulating concentrations of the steroid hormone testosterone (T) during the breeding season. However, many species are territorial also during the non-breeding season, when plasma T levels are basal. The endocrine control of non-breeding territorial aggression differs considerably between species, and previous studies on wintering birds suggest differences between migratory and resident species. We investigated the endocrine modulation of territorial aggression during the breeding and non-breeding season in a resident population of European stonechats (Saxicola torquata rubicola). We recorded the aggressive response to a simulated territorial intrusion in spring and winter. Then, we compared the territorial aggression between seasons and in an experiment in which we blocked the androgenic and estrogenic action of T. We found no difference in the aggressive response between the breeding and the non-breeding season. However, similarly to what is found in migratory stonechats, the hormonal treatment decreased aggressive behaviors in resident males in the breeding season, whereas no effects were recorded in the non-breeding season. When we compared the aggressive responses of untreated birds with those obtained from migratory populations in a previous study, we found that territorial aggression of resident males was lower than that of migratory males during the breeding season. Our results show that in a resident population of stonechats T and/or its metabolites control territorial aggression in the breeding but not in the non-breeding season. In addition, our study supports the hypothesis that migratory status does modulate the intensity of aggressive behavior.     

Riding the tide: intriguing observations of gulls resting at sea during breeding

Adult Lesser Black‐backed Gulls Larus fuscus were followed during the breeding season using a high‐resolution GPS tracking system. Little is known about the foraging movements of these birds and what they do when they are away from the colony. The study revealed intriguing yet infrequent behavioural patterns showing that birds would sit on the sea surface drifting passively with the tidal current for several hours, resting at sea rather than in the breeding colony. The potential function of the observed patterns is discussed as well as the relevance of these observations to other species.     

Effects of geolocator attachments on breeding parameters of Lesser Kestrels

ABSTRACT Light level geolocators, also known as GLS loggers, are electronic devices intended for tracking the location of wide‐ranging animals using ambient light to estimate latitude and longitude. Miniaturized geolocators that can be used on relatively small migratory birds have recently become available, but little is known about the potential harmful effects of geolocators on birds. We examined the possible effects of 1.5‐g geolocators (dimensions: 21 × 6.5 × 9 mm) on the breeding success and survival of migratory Lesser Kestrels (Falco naumanni). During the 2007 breeding season, kestrels were fitted with geolocators using two attachment methods (Teflon wing harnesses and darvic bands), and geolocators were removed in 2008 after the birds returned to the breeding grounds. We found no differences in the breeding success of control and tagged pairs during the 2007 breeding season, but tagged pairs had greater fledgling mortality in the following breeding season. Furthermore, nestlings of tagged individuals had higher triglyceride and uric acid concentrations in their blood than control nestlings during the breeding season following tagging. As for return rates, 75% of tagged birds came back to the colony after the nonbreeding period, a proportion similar to that reported in previous studies. Although back‐mounts are slightly heavier and require more skill to attach, we recommend their use on small migratory raptors because most leg‐mounted geolocators in this study were damaged or rendered useless by dirt obscuring the light sensor.     

Testosterone and its effects on courtship in golden-collared manakins (Manacus vitellinus): seasonal, sex, and age differences

Male golden-collared manakins gather on leks and perform an acrobatic display to attract females. In temperate breeding species, testosterone (T) activation of courtship displays has been well studied. Few studies have examined T activation of displays in tropical species; even fewer have explored the activational role of T in elaborate courtship displays such as in the manakin. In some tropical species, including manakins, territorial aggression or song behavior are uncoupled from T. We have previously shown that T activates display behavior in manakin males when endogenous T levels are low in the non-courtship season. To understand how T functions in breeding birds, we examined T levels in a large group of manakins sampled during the courtship and non-courtship season. In addition, during the courtship season, we gave T implants to adult males, juvenile males, and females. We found that T levels were low during the non-courtship season and comparatively higher on average during the courtship season. However, T levels were low in many adult males during the courtship season, especially when compared to temperate breeding species. Regardless of initial endogenous T levels during the courtship season, T implants did not increase the display frequency of adult males. T-treated females and juvenile males did display under similar conditions. Our data suggest that the effects of T on manakin display vary with season, sex, and age and that high T is not necessary for display.     

Seasonal variation in male testosterone levels in a tropical bird with year‐round territoriality

Testosterone is important in mediating investment in competing activities such as territoriality, parental care, and maintenance behavior. Most studies of testosterone function have focused on temperate species and less is known about the role of testosterone in territoriality or variation in mating systems of tropical species. Results of studies of tropical species with year‐round territoriality indicate that territorial aggression during the non‐breeding season is maintained with low levels of testosterone, and increased levels of testosterone in males during the breeding season may increase mating opportunities or aid in competition for mates. We studied seasonal variation in testosterone levels of male Red‐throated Ant‐tanagers (Habia fuscicauda), a socially monogamous species with year‐round territoriality and with high levels of extra‐pair matings (41% of young), to determine if testosterone levels increased during the breeding season. We captured males during the non‐breeding and breeding seasons and collected blood samples for hormone analysis. We found that mean testosterone concentrations were low during the non‐breeding season (0.18 ± 0.05 [SD] ng/ml, range = 0.11–0.31 ng/ml), and significantly higher during the breeding season (2.37 ± 2.47 ng/ml, range = 0.14–6.28 ng/ml). Testosterone levels of breeding males were not related to aggression levels as measured by attack rates toward a stuffed decoy or singing rates during simulated territorial intrusions. These results suggest that the higher testosterone levels of breeding male Red‐throated Ant‐tanagers may be important in an extra‐pair mating context, possibly in display behavior or mate attraction, but additional study is needed to clarify the role of testosterone during the breeding season.     

Aggression of breeding eastern bluebirds (Sialia sialis) toward their mates and models of intra-and interspecific intruders

Hypotheses regarding the evolution of aggressive patterns during the breeding season in eastern bluebirds (Sialia sialis) were tested by placing models of eastern bluebirds and house sparrows (Passer domesticus) into territories of experimentally naive breeding pairs of eastern bluebirds during three stages of the nesting cycle. The responses of the resident males to models of male bluebirds decreased from the egg-laying to the nestling stage, and this response pattern can be interpreted as support for the protection-of-parentage hypothesis or the nest-site-defence hypothesis. The aggression of resident males to resident females during trials with models of male bluebirds weakly conforms to the pattern predicted by the protection-of-parentage hypothesis. The aggressive response to models of house sparrows also decreased from the egg-laying to the nestling phase in a manner consistent with the nest-site-defence explanation. No aggression toward mates by males or females was observed during trials with house sparrow models, an observation consistent with the predictions of the protection-of-parentage hypothesis.     

The role of androgen receptors in regulating territorial aggression in male song sparrows

This paper examines the role that androgen receptors (ARs) play in modulating aggressive behavior in male song sparrows, Melospiza melodia morphna. Song sparrows are seasonally breeding, territorial birds that maintain year-round territories with male-female pair bonds formed during the spring breeding season. Plasma testosterone levels peak as territories are established and mates acquired. In late summer, testosterone levels fall and remain basal during the non-breeding season. We examined the role of ARs in regulating territorial aggression in captive song sparrows under short- and long-day conditions as well as just prior to, and at the start of the breading season in freely living birds using the nonsteroidal antiandrogen flutamide to block AR function. Birds were implanted with either empty or drug filled silastic implants for 18 to 42 days and then challenged with a novel male decoy to assess the individual birds level of male-male aggression. Freely living birds remained on their home territory and underwent a simulated territorial intrusion, whereas laboratory-held birds were assessed using a laboratory simulated territorial intrusion and remained in their home cage. Experimental treatment of male song sparrows decreased aggressive behavior during the pre-breeding life history substage (March-April) in freely living birds as well as in laboratory-held birds under long-day (16L:8D) conditions. During the early breeding substage (April-May) there was no measurable effect of flutamide treatment on aggressive behavior, nor was there a difference in behavior in the (8L:16D) laboratory birds. This demonstrates that ARs are an important component of the neuroendocrine control of aggressive behavior. Given that flutamide only affected aggression during the pre-breeding substage and in LD birds, the results suggest that AR dependent control of aggressive behavior changes as song sparrow life history states change.     

Phylogénie des touracos (Aves, Musophagidae). Analyse des caractères morphologiques

Phylogeny of turacos (Aves, Musophagidae). Analysis of morphological characters
A cladistic analysis of the 23 species of turacos (Musophagidae) using 34 morphological characters produces, after successive weighting, 4 shortest-length trees (consistency index = 0.76) that present two major clades: the first one with 'grey' turacos (genus Crinifer, Corythaixoides ), the other one with the great blue turaco (genus Corythaeola ) and the turacine bearers turacos (genus Tauraco , Musophaga , Ruwenzorornis , Gallirex ). This result also suggests that the species ' persa ' is not valid; T. schalowi , T. livingstonii , T. corythaix which were included in this species are more closely related to T. fisheri and T. schuettii than they are to T. persa . The polymorphism of these green turacos is also discussed. Ruwenzorornis johnstoni and Gallirex porphyreolophus do not belong to the Tauraco clade nor to the Musophaga clade, but they are closer to the first than to the second. The species Corythaixoides leucogaster is closer to the Crinifer species than to the other Corythaixoides species.     

Does testosterone determine dominance in the house sparrow Passer domesticus? An experimental test

Badges of status function in many birds within a social context to establish dominance hierarchies and reduce antagonistic encounters. In order to maintain the honesty of the signalling system, such badges must be costly to produce or to maintain. The chest bib of the house sparrow functions as a badge of status and changes in size are known to be controlled by testosterone levels. We sought to test the relative importance of testosterone as opposed to bib size in determining dominance within a group of male house sparrows. We did this by manipulating testosterone levels independently during both breeding and post‐breeding seasons in experimental birds and examining the effect of testosterone titre, as well as corticosterone titre relative to bib size on dominance levels. Dominance hierarchies within the groups were tested during both the breeding and post‐breeding phases. We compared the results of these tests with dominance among intact (unmanipulated) birds. Results suggested that the breeding season dominance levels were largely determined by testosterone levels as well as bib size, whereas the post‐breeding dominance levels were determined by post‐breeding testosterone titre and previous breeding season dominance level. Within unmanipulated birds, basal corticosterone levels were significantly, negatively correlated with dominance level, but only during the breeding season. The influence of breeding season dominance on post‐breeding dominance suggests social history is important in determining dominance interactions as well as current testosterone levels and bib size.     

Androgen‐metabolizing enzymes show region‐specific changes across the breeding season in the brain of a wild songbird

The Lapland longspur (Calcarius lapponicus) is an arctic‐breeding songbird that shows rapid behavioral changes during a short breeding season. Changes in plasma testosterone (T) in the spring are correlated with singing but not territorial aggression in males. Also, T treatment increases song but not aggression in this species. In contrast, in temperate‐zone breeders, song and aggression are highly correlated, and both increase after T treatment. We asked whether regional or temporal differences in androgen‐metabolizing enzymes in the longspur brain explain hormone‐behavior patterns in this species. We measured the activities of aromatase, 5α‐reductase and 5β‐reductase in free‐living longspur males. Aromatase and 5α‐reductase convert T into the active steroids 17β‐estradiol (E₂) and 5α‐dihydrotestosterone (5α‐DHT), respectively. 5β‐Reductase deactivates T via conversion to 5β‐DHT, an inactive steroid. We examined seven brain regions at three stages in the breeding season. Overall, aromatase activity was high in the hypothalamus, hippocampus, and ventromedial telencephalon (containing nucleus taeniae, the avian homologue to the amygdala). 5β‐Reductase activity was high throughout the telencephalon. Activities of all three enzymes changed over time in a region‐specific manner. In particular, aromatase activity in the rostral hypothalamus was decreased late in the breeding season, which may explain why T treatment at this time does not increase aggression. Changes in 5β‐reductase do not explain the effects of plasma T on aggressive behavior. © 1999 John Wiley & Sons, Inc. J Neurobiol 41: 176–188, 1999     

Increased survival and breeding performance of double breeders in little penguins Eudyptula minor,New Zealand: evidence for individual bird quality?

The little penguin Eudyptula minor is unique among penguin species in being able to fledge chicks from two clutches in one breeding season. Pairs laying two clutches in a given season make a higher reproductive investment, and may be rewarded by a higher reproductive success as they may raise twice as many chicks as pairs laying one clutch. The higher effort made by pairs laying two clutches could correlate negatively with survival, future reproductive performance or offspring survival, indicating a cost of reproduction. Conversely, a positive relationship between the number of clutches produced in a given breeding season and survival, future reproductive performance or offspring survival would indicate that birds laying two clutches belonged to a category of birds with higher fitness, compared to birds laying only one clutch in the season. In this study we used a long‐term data set taken from an increasing population of little penguins in Otago, SE New Zealand. We modelled the relationship between the number of clutches laid in a breeding season and survival probability, reproductive performance in the next breeding season and first year survival of offspring using capture‐recapture modelling.
Birds laying two clutches produced 1.7 times more fledglings during a breeding season than pairs laying one clutch. We found that birds laying two clutches had a higher probability of breeding in the following breeding season, a higher probability of laying two clutches in the following breeding season and a higher survival probability. There was no overall difference in post‐fledging survival between the young of birds producing one clutch and the young of birds producing two clutches. However, the survival of young of single clutch breeders declined with laying date, whereas the young of double clutch breeders had the same survival rate irrespective of laying date. For a subset of data with birds of known age, we found evidence that the probability of laying two clutches increased with age. However, there were also indications for differences among birds in the tendency to lay two clutches that could not be attributed to age. We tentatively interpret our results as evidence of quality difference among little penguin breeders.     

Gender effects on aggression, dominance rank, and affiliative behaviors in a flock of captive adult cockatiels (Nymphicus hollandicus)

Agonistic and affiliative behaviors and spatial positioning were studied in a small psittacine species, Nymphicus hollandicus. Subjects studied were flock-housed breeders including five hens and seven cocks. Fifteen-minute focal animal samples were collected for the entire flock in a randomly distributed order during mate selection and the onset of the breeding season. All agonistic behaviors were recorded, including the winner and loser of each interaction, along with allopreening and copulation behavior. Point samples were recorded every 60s to determine social spacing. Rates of aggression were significantly higher for male cockatiels than female cockatiels. Results based on dyadic agonistic interactions showed males to rank significantly higher in the social hierarchy than females. Associations within the flock were not random. Individual birds associated more with specific birds than would be predicted by chance. Analysis of spatial data revealed that there were both same-sex and opposite-sex preferred associations within the flock. Male cockatiels engaged in allopreening behavior with females significantly more than with other males. Observations of breeding and nesting behaviors revealed pairs, a triad, and extra-pair mating.     

The phenology of molting,breeding and their overlap in central Amazonian birds

The energetically challenging periods of molting and breeding are usually temporally separated in temperate birds, but can occur simultaneously in tropical birds, a condition known as molt–breeding overlap. Here, we document great variation in the timing and duration of molting and breeding, and in the extent of molt–breeding overlap, among 87 species of understory passerines in central Amazonia. We analyzed molt and breeding from 26 871 birds captured over a 30‐yr period near Manaus, Brazil. Although most species typically bred during the late dry season (about October through January), many thamnophilids apparently bred year‐round, whereas a few other species from a variety of families bred mainly during the wet season (about January through May). Of all breeding birds with an active brood patch, 12.7% were simultaneously molting. Molt–breeding overlap was more frequently observed among suboscines (13.3%), especially thamnophilids (23.0%), than oscines (6.4%). Some families had <5% molt–breeding overlap frequency, including Tyrannidae (4.4%), Tityridae (0.0%), Pipridae (1.5%), Turdidae (0.0%), and Thraupidae (0.0%), indicating that not all tropical species exhibit molt–breeding overlap. Among 31 well‐sampled species (n ≥15 brood patches), variation in molt–breeding overlap frequency was positively correlated with each species’ average duration of flight feather replacement (range 98–301 d). We also measured feather growth rates of individual birds in nine species; in five of these, slower‐growing feathers increased with an individual's probability of having molt–breeding overlap. Among furnariids, molt–breeding overlap occurred either at the beginning or end of the molt cycle, suggesting that physiological mechanisms typically separate molting from breeding. Thamnophilids showed a much different pattern; molt–breeding overlap occurred at any stage of feather replacement, apparently not regulated to be independent of breeding. These results reveal substantial life‐history variation among Amazonian birds. Future work to resolve the physiological regulation of molting and breeding in tropical birds will greatly contribute to understanding these patterns and their relevance to avian diversity.     

Composition of mixed‐species flocks and shifts in foraging location of flocking species on Hainan Island,China

A total of 134 bird species were recorded at Jianfengling, Hainan Island, in China from May 2000 to September 2004, of which 44 participated in one or more of 134 mixed‐species flocks. These flocks averaged 3.8 ± 0.2 species and 20.3 ± 1.2 individuals. Flocking propensity in a given species ranged from 1.5 to 100%. For flocking species, frequency of flocking and number of individuals in flocks was positively correlated with frequency and number in point counts. Among all species pairs with flocking frequency above 5%, cluster and correlation analysis indicated there were two principal groups of flocking birds – canopy species and understorey species: associations were positive within a group, but negative between groups. Canopy birds had a higher flocking propensity than understorey birds. They also made significantly less use of inner branches and trunks and greater use of middle branches, and foraged at a significantly greater height when in mixed‐species flocks than when solitary. For understorey bird species, there were no significant differences in foraging locations between solitary and mixed‐species flocks. Higher flocking frequency occurred in the wet season for canopy birds, but in the dry season for understorey birds. Overall patterns were consistent with the explanation that flocking enables an expansion of foraging niche by reducing the risk of predation.     

Predicting release success of captive‐reared loggerhead shrikes (Lanius ludovicianus) using pre‐release behavior

We assessed whether behavioral markers could be used to evaluate pair compatibility and predict pair bond success of captive‐reared San Clemente loggerhead shrikes (Lanius ludovicianus mearnsi) released into the wild. Potential breeding pairs of shrikes were introduced at the Zoological Society of San Diego's captive‐breeding facility and then moved to release cages located in suitable but unoccupied habitat. Courting pairs were affected negatively by the disturbance of translocation to a new location and generally needed a few days to reinitiate pair bonding in the release enclosures. We separated and returned pairs to captivity when intra‐pair aggression or cessation of all courtship behavior occurred; all other pairs were released into the wild. The rate of nest approaches was the best marker to predict a successful release into the wild (i.e., pairs that remained near the release site and attempted to breed). Additionally, all experienced breeding pairs (i.e., pairs with males and females with prior captive breeding experience) exhibiting nesting behavior were successful, although previous experience alone does not ensure post‐release breeding. Results from this study indicate the importance of assessing behaviors of individuals paired for population augmentation. In using behavioral cues, identifying pairs with a low probability of success is possible, and replacing these pairs with individuals that have a higher likelihood of post‐release success can occur. This strategy will be important to efficiently restore imperiled populations of endangered species while working within temporal and financial constraints. Zoo Biol 0:1–12, 2005. © 2005 Wiley‐Liss, Inc.     

Pair bond and breeding success in Blue Tits Parus caeruleus and Great Tits Parus major

Data from 939 nests of the Blue Tit Parus caeruleus and 1008 nests of the Great Tit P. major from nestboxes provided in superabundance in mixed forest study sites between 1976 and 2001 were analysed to examine the effects of mate retention on breeding success and the relationship between mate fidelity and site fidelity. Most birds retained their former partner (76% in Great Tits and 65% in Blue Tits). The probability of a pair divorcing was affected by male age in Great Tits, divorce being more likely in pairs with first‐year males. Great Tit pairs breeding together for a second season bred earlier, but had no higher breeding success than pairs breeding together for the first time. In Blue Tits laying date and start of incubation tended to be earlier in pairs breeding together for a second season, but hatching and fledging dates were not earlier than in other pairs. Great Tit pairs breeding together for two consecutive seasons bred earlier in the second season than in the first, but breeding success did not differ significantly between years. In both species, breeding performance did not differ between pairs that divorced after a season and pairs that stayed together. Thus breeding success did not determine whether a pair divorced or bred together again. Neither Blue Tits nor Great Tits improved their breeding performance through divorce. Blue Tit females even had fewer fledglings in the year after divorce than in the year before. Mate retention affected breeding site fidelity. Blue Tit females had greater breeding dispersal distances between consecutive years when re‐mating than when breeding again with the same mate. In Great Tits both males and females dispersed more when re‐mating than when retaining the former partner, suggesting that mate retention increased the chance of retaining the breeding site. In both species, breeding dispersal distances did not differ between pairs that divorced and pairs in which one mate disappeared. Because no major advantage of mate retention was evident, we suggest that mate retention evolved under different conditions than those found in study sites with high breeding densities and a superabundance of artificial nesting sites.     

Diversity of migration strategies among great frigatebirds populations

Migratory behavior varies extensively between bird taxa, from long distance migration to purely sedentary behavior. Variability in migratory behavior also occurs within taxa, where individuals within some species, or even populations, show mixed strategies. The same variability occurs in seabird species. We examined the migratory behavior of distinct populations of great frigatebirds Fregata minor in three distant oceanographic basins. Great frigatebird populations showed extensive variation in post‐breeding migratory behavior. Birds from Europa Island (Mozambique Channel) made long‐distance migration to numerous distinct roosting sites in the Indian Ocean, New Caledonia birds made shorter distance migrations to roosting sites in the southwestern Pacific Ocean, and Galapagos birds were resident within the archipelago year round. Juvenile birds from Europa Is. and New Caledonia dispersed widely whereas Galapagos juveniles were resident year round. The migratory behavior of Europa Is. and New Caledonia resulted in complete separation of foraging grounds between breeding adults, non‐breeding adults, and juveniles, whereas in the Galapagos the overlap was complete. We suggest that population variability in migratory behavior may have arisen because of different environmental conditions at sea, and also depends on the availability of suitable roosting sites on oceanic islands. The results also highlight the capacity of frigatebirds to remain airborne most of the time even outside the breeding season when they have to molt.     

Brain aromatase, 5α‐reductase,and 5β‐reductase change seasonally in wild male song sparrows: Relationship to aggressive and sexual behavior

In many species, territoriality is expressed only during the breeding season, when plasma testosterone (T) is elevated. In contrast, in song sparrows (Melospiza melodia morphna), males are highly territorial during the breeding (spring) and nonbreeding (autumn) seasons, but not during molt (late summer). In autumn, plasma sex steroids are basal, and castration has no effect on aggression. However, inhibition of aromatase reduces nonbreeding aggression, suggesting that neural steroid metabolism may regulate aggressive behavior. In wild male song sparrows, we examined the neural distribution of aromatase mRNA and seasonal changes in the activities of aromatase, 5α‐, and 5β‐reductase, enzymes that convert T to 17β‐estradiol, 5α‐dihydrotestosterone (5α‐DHT, a potent androgen), or 5β‐DHT (an inactive metabolite), respectively. Enzyme activities were measured in the diencephalon, ventromedial telencephalon (vmTEL, which includes avian amygdala), caudomedial neostriatum (NCM), and the hippocampus of birds captured during spring, molt, or autumn. Aromatase and 5β‐reductase changed seasonally in a region‐specific manner. Aromatase in the diencephalon was higher in spring than in molt and autumn, similar to seasonal changes in male sexual behavior. Aromatase activity in the vmTEL was high in both spring and autumn but significantly reduced at molt, similar to seasonal changes in aggression. 5β‐Reductase was not elevated during molt, suggesting that low aggression during molt is not a result of increased inactivation of androgens. These data highlight the relevance of neural steroid metabolism to the expression of natural behaviors by free‐living animals. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 209–221, 2003     

Species‐specific foraging strategies and segregation mechanisms of sympatric Antarctic fulmarine petrels throughout the annual cycle

Determining the year‐round distribution and behaviour of birds is necessary for a better understanding of their ecology and foraging strategies. Petrels form an important component of the high‐latitude seabird assemblages in terms of species and individuals. The distribution and foraging ecology of three sympatric fulmarine petrels (Southern Fulmar Fulmarus glacialoides, Cape Petrel Daption capense and Snow Petrel Pagodroma nivea) were studied at Adélie Land, East Antarctica, by combining information from miniaturized saltwater immersion geolocators and stable isotopes from feathers. During the breeding season at a large spatial scale (c. 200 km), the three species overlapped in their foraging areas located in the vicinity of the colonies but were segregated by their diet and trophic level, as indicated by the different chick δ¹⁵N values that increased in the order Cape Petrel < Southern Fulmar < Snow Petrel. During the non‐breeding season, the three fulmarines showed species‐specific migration strategies along a wide latitudinal gradient. Snow Petrels largely remained in ice‐associated Antarctic waters, Southern Fulmars targeted primarily the sub‐Antarctic zone and Cape Petrels migrated further north. Overall, birds spent less time in flight during the non‐breeding period than during the breeding season, with the highest percentage of time spent sitting on the water occurring during the breeding season and at the beginning of the non‐breeding period before migration. This activity pattern, together with the δ¹³C values of most feathers, strongly suggests that moult of the three fulmarine petrels occurred at that time in the very productive high Antarctic waters, where birds fed on a combination of crustaceans and fish. The study highlights different segregating mechanisms that allow the coexistence of closely related species, specifically, prey partitioning during the breeding season and spatial segregation at sea during the non‐breeding season.