Incubation Behavior Research Articles

Ecological, evolutionary, and conservation implications of incubation temperature‐dependent phenotypes in birds

Incubation is a vital component of reproduction and parental care in birds. Maintaining temperatures within a narrow range is necessary for embryonic development and hatching of young, and exposure to both high and low temperatures can be lethal to embryos. Although it is widely recognized that temperature is important for hatching success, little is known about how variation in incubation temperature influences the post-hatching phenotypes of avian offspring. However, among reptiles it is well known that incubation temperature affects many phenotypic traits of offspring with implications for their future survival and reproduction. Although most birds, unlike reptiles, physically incubate their eggs, and thus behaviourally control nest temperatures, variation in temperature that influences embryonic development still occurs among nests within a population. Recent research in birds has primarily been limited to populations of megapodes and waterfowl; in each group, incubation temperature has substantial effects on hatchling phenotypic traits important for future development, survival, and reproduction. Such observations suggest that incubation temperature (and incubation behaviours of parents) is an important but underappreciated parental effect in birds and may represent a selective force instrumental in shaping avian reproductive ecology and life-history traits. However, much more research is needed to understand how pervasive phenotypic effects of incubation temperature are among birds, the sources of variation in incubation temperature, and how effects on phenotype arise. Such insights will not only provide foundational information regarding avian evolution and ecology, but also contribute to avian conservation.

Elevated corticosterone levels and severe weather conditions decrease parental investment of incubating Adélie penguins

Corticosterone, the main stress hormone in birds, mediates resource allocation, allowing animals to adjust their physiology and behaviour to changes in the environment. Incubation is a time and energy-consuming phase of the avian reproductive cycle. It may be terminated prematurely, when the parents' energy stores are depleted or when environmental conditions are severe. In this study, the effects of experimentally elevated baseline corticosterone levels on the parental investment of incubating male Adélie penguins were investigated. Incubation duration and reproductive success of 60 penguins were recorded. The clutches of some birds were replaced by dummy eggs, which recorded egg temperatures and rotation rates, enabling a detailed investigation of incubation behaviour. Corticosterone levels of treated birds were 2.4-fold higher than those of controls 18days post treatment. Exogenous corticosterone triggered nest desertion in 61% of the treated birds; consequently reducing reproductive success, indicating that corticosterone can reduce or disrupt parental investment. Regarding egg temperatures, hypothermic events became more frequent and more pronounced in treated birds, before these birds eventually abandoned their nest. The treatment also significantly decreased incubation temperatures by 1.3°C and lengthened the incubation period by 2.1days. However, the number of chicks at hatching was similar among successful nests, regardless of treatment. Weather conditions appeared to be particularly important in determining the extent to which corticosterone levels affected the behaviour of penguins, as treated penguins were more sensitive to severe weather conditions. This underlines the importance of considering the interactions of organisms with their environment in studies of animal behaviour and ecophysiology.

Plasticity in incubation behaviour under experimentally prolonged vulnerability to nest predation

Nest predation is the main cause of nest failures in many bird species. To counter this, birds have evolved different behavioural strategies to decrease the visibility of their nests, thus reducing the probability of nest detection. We manipulated the long-term perception of nest predation risk in pied flycatchers (Ficedula hypoleuca) by experimentally increasing the nest vulnerability to predators. We placed treatment and control nest-boxes for breeding pied flycatchers that appeared identical during the initial phase of breeding. But after the removal of a front panel, treatment boxes had an enlarged entrance hole, almost twice the initial diameter. This treatment increases actual predation risk and presumably parental perception of risk. Control boxes presented instead an entrance hole of the same size both before and after the manipulation. When breeding in enlarged entrance holes, females doubled the vigilance at the nest while males reduced the time spent at the nest, compared to pied flycatchers breeding in control boxes. Increased vulnerability of the nest site to predation risk, thus, induced pied flycatcher parents to increase nest vigilance while reducing their activity at the nest. These results highlight the existence of plasticity in incubation behaviours under long-term experimentally increased nest predation risk.

Microhabitats for Oviposition and Male Clutch Attendance in Hyalinobatrachium aureoguttatum (Anura: Centrolenidae)

In this study we describe for the first time aspects of the reproductive ecology and behavior of a population of Hyalinobatrachium aureoguttatum located in the Colombian Pacific lowlands. Males vocalize and attend clutches from the underside of leaves overhanging the streams. Males showed high fidelity to their territory; each male repeatedly uses the same leaf for perching, calling, mating, and clutch attendance. There were no significant differences in the environmental variables registered for the microhabitats where males were located with or without clutches, with one or multiple clutches, or between successful or unsuccessful clutches, which suggest that the analyzed variables are not important for the obtention of the clutches and their success. Males were found grouped in the study area at distances varying between 0.3–0.5 m; thus, more than one male can be observed occupying other leaves in the same plant. Fights or aggressive behaviors were not observed in intrusion events by co-specific males in the territory of the resident males; however, we registered a series of movements that resulted in moving the intruder further away. Females almost immediately abandoned the clutches after oviposition, whereas most of the time, at day and night, males stayed near, touching or sitting on one to five egg clutches during most of their embryonic development. This brooding behavior also included hydration, cleaning, and defense of the eggs. Arthropod predation was observed in both attended and abandoned egg clutches; however, in one observation, the behavior of the male moved the predator away and saved the clutch. These observations and the finding of abandoned clutches that did not complete their development suggest that male parental care increases embryo survival and, as a result, his reproductive success.

Local Temperature and not Latitude Determines the Design of Blue Tit and Great Tit nests

Recent studies are documenting the extent to which the mass and construction of bird nests varies between individuals and locations. In the Blue Tit ( Cyanistes caeruleus) and Great Tit ( Parus major), temperatures experienced by females during nest construction are inversely related to nest mass. Moreover, Mainwaring et al. ( Journal of Biogeography, 2012) showed that nests constructed at high latitude are heavier and better insulated than nests built by conspecifics in the south. Although mean spring temperature was used as a proxy for latitude in the Mainwaring et al. study, it remains untested whether individual birds build nests in response to a narrower range of temperatures experienced at the start of the breeding season. Our study showed that irrespective of latitude nest mass, and in particular nest cup mass, of Blue Tits and Great Tits was significantly affected by the temperature experienced by the birds for the seven days preceding clutch initiation. Similar results were seen with the insulatory properties of nests. The potential impact of variation in nest construction and insulation on subsequent incubation and chick-rearing behaviour is discussed.

About the Cover.

Next article FreeAbout the CoverFull TextPDF Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverParental care of eggs or young is uncommon in invertebrates. This is true for most squids, but as John Bower and colleagues report in this issue (pages 259–262), females of a species in northern Japan care for their spawned eggs by brooding them in their arms. Divers in northern Japan have observed this behavior annually in nearshore waters off the Shiretoko Peninsula since 1991, but the species has until now remained unidentified.The cover photo, taken off Rausu, Hokkaido, in May 2006 at about 20-m depth, shows a female brooding a single-layer, sheet-like egg mass attached to its arm hooks. The small, oval eggs are visible within the dark, viscous material that formed the egg mass. The authors describe the brooding behavior and identify the species as Gonatus madokai (family Gonatidae), now the third squid species known to brood. They suggest that females might continue this behavior for several months, during which time they weaken, undergo gelatinous degeneration, and are presumably unable to feed.Why the females would devote so much time and energy to caring for the eggs remains a mystery, but brooding could increase offspring fitness by protecting the developing embryos from egg predators and hypoxia. Even less is known about the evolutionary origin of this behavior, but the authors suggest that more brooding squids await discovery in the deep sea, which could provide more clues to understanding this intriguing behavior.Credits: Photo, Katsunori Seki, Shiretoko Diving Kikaku, Rausu, Hokkaido, Japan; cover design, Beth Liles, Marine Biological Laboratory. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 223, Number 3December 2012 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/BBLv223n3cover Views: 64 © 2012 by Marine Biological Laboratory. All rights reserved. Crossref reports no articles citing this article.

Faithful females receive more help: the extent of male parental care during incubation in relation to extra‐pair paternity in songbirds

Parental care provided by males occurs in a diverse array of animals and there are large differences among species in its extent compared with female care. However, social and ecological factors responsible for interspecific differences in male's share of parental duties remain unclear. Genetic fidelity of females has been long considered important. Theory predicts that females should receive more help from their mates in raising the offspring in species with high genetic fidelity. Using avian incubation behaviour as a model system, we confirmed this prediction. The extent of male's help during incubation increased with decreasing rate of extra-pair paternity across species (22 species of socially monogamous songbirds from 13 families; male's share of incubation ranged from 6% to 58%), even after accounting for covariates, biases in species selection and intraspecific variability. Moreover, this result was not sensitive to two different phylogenies and branch length estimates. We suggest that our findings support the notion, backed by theory, that genetic fidelity is an important factor in the evolution of male parental care. We offer several behavioural scenarios for the coevolution between male's share of parental duties and the genetic mating system.

Pelvic-fin brooding in a new species of riverine ricefish (Atherinomorpha: Beloniformes: Adrianichthyidae) from Tana Toraja, Central Sulawesi, Indonesia

A new species of ricefi sh is described from a hill stream in Tana Toraja, Sulawesi. Oryzias eversi, new species, is distinguished from all other adrianichthyids in Sulawesi by having a low number of fi n rays in anal (17-18 (19)) and dorsal (10-12) fi ns, only 33-36 scales in lateral midline, ½14 transverse scale rows at dorsal fi n origin, 30-32 (33) vertebrae, small eyes (28.2-35.5% of head length), a conspicuous blackish male courtship colouration, and brooding behaviour similar to lacustrine ricefi shes. Female Oryzias eversi carry the eggs until the embryos hatch, and show a conspicuous abdominal concavity and extended fi ns, accommodating and holding the clutch of eggs. The eggs are connected to the female for the whole time of development by attaching fi laments that protrude from the female's urogenital pore. A mitochondrial haplotype phylogeny suggests that the new species is closely related to another pelvic the lake-dwelling O. sarasinorum from Lake Lindu in Central Sulawesi. However, the haplotype group of O. eversi and O. sarasinorum is nested within a clade of egg-depositing Oryzias from central, southwest, and southeast Sulawesi, whereas another brooder, Adrianichthys oophorus from Lake Poso, forms a distinct, second lineage of Sulawesi's ricefi shes. Accordingly, the brooding strategy has probably evolved more than once and may be realised in river habitats, which represents a new evolutionary trajectory in the radiation of ricefi shes in Sulawesi. The present discovery adds another new ricefi sh species to Sulawesi's still only partially known ichthyofauna, and highlights the island's role as hotspot of adrianichthyid diversity.

Using Age-Based Life History Data to Investigate the Life Cycle and Vulnerability of Octopus cyanea

Octopus cyanea is taken as an unregulated, recreationally fished species from the intertidal reefs of Ningaloo, Western Australia. Yet despite its exploitation and importance in many artisanal fisheries throughout the world, little is known about its life history, ecology and vulnerability. We used stylet increment analysis to age a wild O. cyanea population for the first time and gonad histology to examine their reproductive characteristics. O. cyanea conforms to many cephalopod life history generalisations having rapid, non-asymptotic growth, a short life-span and high levels of mortality. Males were found to mature at much younger ages and sizes than females with reproductive activity concentrated in the spring and summer months. The female dominated sex-ratios in association with female brooding behaviours also suggest that larger conspicuous females may be more prone to capture and suggests that this intertidal octopus population has the potential to be negatively impacted in an unregulated fishery. Size at age and maturity comparisons between our temperate bordering population and lower latitude Tanzanian and Hawaiian populations indicated stark differences in growth rates that correlate with water temperatures. The variability in life history traits between global populations suggests that management of O. cyanea populations should be tailored to each unique set of life history characteristics and that stylet increment analysis may provide the integrity needed to accurately assess this.

Shorebird incubation behaviour and its influence on the risk of nest predation

Both nest survival and incubation behaviour are highly variable among shorebirds (Charadrii), and we tested whether more conspicuous incubation behaviour increased the risk of nest predation. During 2000–2006, we monitored nest fate at 901 shorebird nests at three study sites across the circumpolar Arctic. Using miniature video recorders and nest temperature sensors, we obtained 782 days of behavioural data for 161 nests of 11 species. We related nest fate to the rate and duration of adults' nest absences or restless movements on the nest, as well as the total proportion of each day that adult birds engaged in these activities. Nest predation was positively related to the proportion of time that each species left the nest unattended. After controlling for species effects, the likelihood of a successful nesting attempt was lower for individuals that spent more time off the nest, but among failed nests, the number of days that a nest survived prior to depredation was not significantly predicted by measures of incubation behaviour. To control for weather or seasonal effects, we paired observations from nests that were ultimately depredated with observations from successful nests of the same species on the same day. In this paired sample (dominated by two species: red phalaropes, Phalaropus fulicarius, and little stints, Calidris minuta), both incubation recesses and restless movements were more numerous among failed versus successful nests. Our results suggest that more conspicuous incubation behaviour is indeed related to a higher risk of nest predation, and that this relationship may underlie patterns of nest survival within and among shorebird species.

Avian life history traits influence eggshell bacterial loads: a comparative analysis

Selection pressures due to parasitism play an important role in driving the evolution of life history traits of birds in general and of behaviour at the nest in particular. Eggshell bacterial load has been shown to predict hatching failure (i.e. the probability of embryo infection) but the relationships between the bacterial environment of the nest and life history characteristics of birds remain poorly investigated. We explored interspecific variation in eggshell bacterial load of mesophilic bacteria,Enterococcusspp.,Staphylococcusspp. andEnterobacteriaceaegroups across 24 bird species and assessed whether bacterial load is associated with breeding traits. Interspecific variation was much higher than intraspecific variation for all measures of bacterial load even after controlling for annual variation. Thus, we were able to assess the correlation between bacterial community characteristics and life history traits. After correcting for phylogenetic effects, we found that nest type, the use of feathers or plants as lining material, and incubation behaviour explained a significant proportion of the variance in bacterial communities on eggshells. The strength of these associations depended on study year, suggesting an important role of environmental conditions for eggshell bacterial load or community. Overall, these results suggest that bacteria on eggshells are associated with bird species traits, probably because birds are mediating the deleterious effect of eggshell microbes through behavioural traits that modify bacterial load.

High Coordination and Equitable Parental Effort in the Rufous Hornero

Abstract. In temperate regions of the Southern Hemisphere, avian parental care is understudied, in particular for the neotropical family Furnariidae. We measured rates of nest building, mud carrying, incubation, brooding, feeding, and nest-sanitation behaviors of molecularly sexed Rufous Horneros (Furnarius rufus) nesting in the humid pampas of Argentina. We also evaluated the coordination of all these behaviors between the partners, and compared the frequency of uncoordinated behaviors of each sex. Males and females worked equitably throughout the nesting cycle with few exceptions: (1) both sexes built the nest, but males supplied somewhat less mud at the beginning of nest construction, (2) though highly involved in incubating the eggs males did so slightly less often than females during early incubation, (3) even if males also brooded the nestlings, they brooded less often and for slightly briefer periods than did females, and (4) young nestlings were fed less often by males than by females. We found no...

Neuroendocrine regulation of rearing behavior in the native Thai hen

Vasoactive intestinal peptide (VIP) is the avian prolactin releasing factor and changes in the concentrations of plasma prolactin (PRL) are found during the avian reproductive cycle. This study investigated the changes in the VIP/PRL system of native Thai hens rearing their young as compared to hens deprived of rearing their chicks. The number of VIP-immunoreactive (VIP-ir) neurons in the Nucleus inferioris hypothalami (IH) and Nucleus infundibuli hypothalami (IN) of hens rearing chicks (R) were compared with those of non-rearing chicks (NR). Plasma PRL levels were determined by enzyme-linked immunosorbent assay. The localization and number of VIP-ir neurons were determined by immunohistochemistry. The numbers of VIP-ir neurons in the IH–IN areas were high in the R hens, whereas the number of VIP-ir neurons decreased in the NR hens as compared to their respective R hens. During the rearing period, changes in the VIP-ir neurons within the IH–IN were correlated with plasma PRL levels. The results of the present study indicate for the first time that the VIP/PRL system plays a role in neuroendocrine reorganization to establish maternal behavior in native Thai chickens. The VIP/PRL system functions not only as a well established key regulator of incubation behavior, but is also involved in the regulation of rearing behavior. It is possible that VIP and the decline in the number of VIP-ir neurons and in turn VIPergic activity and the decrease in PRL levels are related to their contribution to rearing behavior of this non-seasonal breeding, equatorial precocial species.

Do Brooding Pythons Recognize their Clutches? Investigating External Cues for Offspring Recognition in the Children's Python, Antaresia childreni

AbstractParental care provides substantial benefits to offspring but exacts a high cost to parents, necessitating the evolution of offspring recognition systems when the risk of misdirected care is high. In species that nest, parents can use cues associated with the offspring (direct offspring recognition) or the nest (indirect offspring recognition) to reduce the risk of misdirected care. Pythons have complex parental care, but a low risk of misdirected care. Thus, we hypothesized that female Children's pythons (Antaresia childreni) use indirect cues to induce and maintain brooding behavior. To test this, we used a series of five clutch manipulations to test the importance of various external brooding cues. Contrary to our hypothesis, we found that female A. childreni are heavily internally motivated to brood, needing only minimal external cues to induce and maintain egg‐brooding behavior. Females were no more likely to brood their own clutch in the original nest as they were to brood a clutch from a conspecific, a pseudoclutch made from only the shells of a conspecific, or their clutch in a novel nest. The only scenario where brooding was reduced, but even then not eliminated, was when the natural clutch was replaced with similarly sized stones. These results suggest that egg recognition in pythons is similar to that of solitary‐nesting birds, which have similar nesting dynamics.

Context-dependent costs of incubation in the pied flycatcher

Although previously disputed, it is now clear that the demands from avian incubation put parents under considerable energetic stress, sometimes to an extent where the costs of incubation constrain clutch size evolution. However, the behavioural mechanisms involved in manifesting such costs remain largely unknown. We manipulated the demands of incubation by enlarging and reducing clutch size during 2 years in a pied flycatcher, Ficedula hypoleuca, population in southern Sweden, and measured the resulting effects on incubation temperature and incubation behaviour. In addition, we assessed possible effects on later reproductive stages by restoring clutch size prior to hatching and subsequently monitoring female nest provisioning and nestling growth rate. The length of both attentive and inattentive bouts, as well as the total time spent incubating, was longer for females incubating enlarged clutches. These females also maintained eggs at lower temperatures, but only at the beginning of incubation. Thus, increased incubation demands were met by investing more time in incubation, but females were still not able to maintain incubation temperature at the same level as control females. Furthermore, females paid costs of increased incubation demands in terms of a longer incubation period in both years, and reduced nestling production in one, but did not appear to transfer any additional costs to their nestlings. We conclude that costs of incubation are context dependent, and suggest that the demands from incubation may be important in brood size determination in this species, at least in deteriorating ambient conditions. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. (Less)

How avian incubation behaviour influences egg surface temperatures: relationships with egg position, development and clutch size

While understanding heat exchange between incubating adults and their eggs is central to the study of avian incubation energetics, current theory based on thermal measurements from dummy eggs reveals little about the mechanisms of this heat exchange or behavioural implications for the incubating bird. For example, we know little about how birds distribute their eggs based on temperature differences among egg positions within the nest cup. We studied the great tit Parus major, a species with a large clutch size, to investigate surface cooling rates of individual eggs within the nest cup across a range of ambient temperatures in a field situation. Using state‐of‐the‐art portable infrared imaging and digital photography we tested for associations between egg surface temperature (and rate of cooling) and a combination of egg specific (mass, shape, laying order, position within clutch) and incubation specific (clutch size, ambient temperature, day of incubation) variables. Egg surface temperature and cooling rates were related to the position of the eggs within the nest cup, with outer eggs being initially colder and cooling quicker than central eggs. Between foraging bouts, females moved outer eggs significantly more than centrally positioned eggs. Our results demonstrate that females are capable of responding to individual egg temperature by moving eggs around the nest cup, and that the energy cost to the female may increase as incubation proceeds. In addition, our results showing that smaller clutches experience lower initial incubation temperatures and cool quicker than larger clutches warrant further attention for optimal clutch size theory and studies of energetic constraints during incubation. Finally, researchers using dummy eggs to record egg temperature have ignored important elements of contact‐incubation, namely the complexity of how eggs cool and how females respond to these changes.

The Application of Temperature Data Loggers for Remotely Monitoring the Nests of Emei Shan Liocichla (Liocichla omeiensis)

Temperature data loggers (TDL) are mostly used to monitor avian incubation behavior in bird studies. In this paper we demonstrate how TDL can also be used to determine different breeding stages and nest success of the vulnerable Emei Shan Liocichla (Liocichla omeiensis). All nests that contained at least one egg were divided into two groups. Group I included six nests monitored traditionally by the observers' visits, while Group II included eight nests monitored by TDL. Group I and Group II were visited every 1-4 days and 7 days, respectively, to check nest contents and status (e.g., active vs. inactive, and the breeding process) until fledging or nest failure. The time of each observation was recorded to verify the interpretation of TDL. The data recorded by TDL were converted into line graphs of temperature against time and assessed visually. The results indicated that TDL can reliably identify different breeding stages and estimate daily nest survival rates (DSR) and total nest success. The nest success of Group II (0.3015) was higher than that of Group I (0.2387), suggesting that deployment of TDL did not negatively influence nest survival rate of Emei Shan Liocichla. In contrast to traditional nest visits, TDL minimized disturbance by observers and provided a more precise estimate of nest survival. We suggest that TDL should be used more widely in studies of the breeding ecology of rare and endangered birds.

Are coastal lagoons physically or biologically controlled ecosystems? Revisiting r vs. K strategies in coastal lagoons and estuaries

Environmental stress influences biological assemblages, with species responding to stress by adopting particular life-history strategies (e.g., r vs. K). Coastal lagoons and estuaries are considered naturally stressed and physically controlled systems with frequent environmental disturbances and fluctuations. At the same time, their transitional nature (between terrestrial, freshwater and marine) makes them especially vulnerable to human impacts and land and freshwater inputs. As a result, it is hypothesised that residents of coastal lagoons would display characteristics of r-selected species. The r-strategy involves increased reproductive effort through early reproduction, small and numerous offspring with a large dispersive capability, short lifespan and small adult body size. Together, these traits provide a selective advantage in such unpredictable or short-lived environments. Alternatively, immigrants to coastal lagoons should mostly be K-strategists, with a competitive advantage over the r-strategists, at least on a temporary time scale. These hypotheses were explored using a dataset from 73 Atlanto-Mediterranean sites: 27 estuaries, 42 coastal lagoons and 4 from the sea, obtained from published sources. A detailed analysis of the distributions of the different resident fish species according to lagoon characteristics indicated that in lagoons with a higher marine influence the families Gobiidae, Blenniidae and Syngnathidae were common, while lagoons with freshwater influence are characterized by Cyprinidae and other freshwater species. In analyzing the biological strategies of lagoon species we found that fish assemblages inhabiting marine influenced lagoons were characterized by solitary, necto-benthonic sedentary species. These species are often hermaphroditic, with benthic broods and many exhibit brooding behaviour. This suggests that marine influenced lagoons are dominated by K-strategist species, while r-strategy species will be more common in freshwater lagoons and among marine migrant species.

A Novel Mode of Colony Formation in a Hydrozoan through Fusion of Sexually Generated Individuals

Coloniality, as displayed by most hydrozoans, is thought to confer a size advantage in substrate-limited benthic marine environments and affects nearly every aspect of a species' ecology and evolution. Hydrozoan colonies normally develop through asexual budding of polyps that remain interconnected by continuous epithelia. The clade Aplanulata is unique in that it comprises mostly solitary species, including the model organism Hydra, with only a few colonial species. We reconstruct a multigene phylogeny to trace the evolution of coloniality in Aplanulata, revealing that the ancestor of Aplanulata was solitary and that coloniality was regained in the genus Ectopleura. Examination of Ectopleura larynx development reveals a unique type of colony formation never before described in Hydrozoa, in that colonies form through sexual reproduction followed by epithelial fusion of offspring polyps to adults. We characterize the expression of manacle, a gene involved in foot development in Hydra, to determine polyp-colony boundaries. Our results suggest that stalks beneath the neck do not have polyp identity and instead are specialized structures that interconnect polyps. Epithelial fusion, brooding behavior, and the presence of a skeleton were all key factors behind the evolution of this novel pathway to coloniality in Ectopleura.

Ocean climate variability links incubation behaviour and fitness in Ancient Murrelets (Synthliboramphus antiquus)

Large-scale interannual and decadal variation in ocean conditions, including sea-surface temperature (SST) has been shown to affect the breeding behaviour of marine birds in the North Pacific. However, as individual species respond differently to changing food supplies, our understanding of the role of climate variation in seabirds is limited. To examine the effect of ocean conditions on breeding behaviour, we measured incubation shift lengths of Ancient Murrelet ( Synthliboramphus antiquus (Gmelin, 1789)), a small marine bird with exceptionally long incubation shift length, in seven, nonconsecutive years. We compared variation in shift length with interyear variation in regional SST. Incubation shifts were longer in years when March–May SST was higher. In years with longer shift length, birds have lower reproductive success. Our results suggested that Ancient Murrelets on Haida Gwaii can adjust their incubation patterns by extending their shift length in relation to SST fluctuations during breeding season.