Journal of Avian Biology最新文献

We studied the migration of Magellanic penguins near the southern tip of the breeding distribution, and for the first time found evidence of partial migration for this species within the same colony. Forty-three percent of the penguins studied stayed within ~ 290 km of the colony (residents), while others went northwards as far as 2000 km. All penguins spent the same amount of time at sea and traveled similar total distances, but residents experienced colder waters (2°C lower) and habitats with lower Chlorophyll-a concentrations than migrants. The two habitats are inhabited by different prey items, consequently offering the penguins distinct prey options. We have shown high variability in the non-breeding dispersion behavior of Magellanic penguins within the same colony; nonetheless, further research is required to understand the proximate and ultimate causes, and the consequences, of this behavior.

Vocalisations are widely used to signal behavioural intention in animal communication, but may also carry acoustic signatures unique to the calling individual. Here, we used acoustic analysis to confirm that Manx shearwater Puffinus puffinus calls carry individual signatures, and discerned which features made the calls individual. Manx shearwater are nocturnal seabirds that breed in dense colonies, where they must recognize and locate mates among thousands of conspecifics calling in the dark. There is evidence for mate vocal recognition in two shearwater species, but quantitative data on the vocalisations are lacking. We elicited vocal responses to playback of conspecific calls in Manx shearwaters, and measured spectral and temporal parameters of the calls. We then applied linear discriminant analysis with leave-one-out cross-validation and could confirm the presence of individual vocal signatures. We then calculated among-individual repeatability of 34 features describing the vocalisation to determine the extent to which these features may contribute to individual signature coding. We found that calls cluster by individual in both temporal and spectral characteristics, suggesting these traits are contributing to Manx shearwaters' unique call signatures.

Breath-hold diving presents air-breathing vertebrates with the challenge of maintaining aerobic respiration while exercising underwater. Adaptive increases in the oxygen (O₂) storage capacity in the lungs, blood, or muscle tissues can enhance these reserves and greatly extend aerobic foraging time underwater. Here, we report blood- and muscle-O₂ storage parameters (blood hemoglobin concentration ([Hb]), hematocrit, and myoglobin concentration ([Mb]) in the pectoralis and gastrocnemius) for 16 species of diving and dabbling ducks found in North America, and investigate which parameters are correlated with the diving behaviors reported in both the sea ducks (Mergini) and the pochards (Aythini). Both [Hb] in the blood and [Mb] in the gastrocnemius, a major leg muscle used in propulsion for these predominantly leg-propelled divers, were significantly higher in the sea ducks compared to the dabblers (Anatini). The pochards also showed a significant increase in [Hb] and were intermediate between the sea ducks and the dabblers in hematocrit and [Mb] in the gastrocnemius. Among these four variables and total body mass, [Mb] in the gastrocnemius was the most significant predictor of mean species dive time, and these two variables were correlated across the phylogeny. Our results indicate that the observed changes in O₂ storage capacity in the blood and muscles are positively correlated with diving behavior in two clades of ducks, such that larger increases are correlated with longer dive times.

Measuring parental care behaviour in the wild is central to the study of animal ecology and evolution, but it is often labour- and time-intensive. Efficient open-source tools have recently emerged that allow animal behaviour to be quantified from videos using machine learning and computer vision techniques, but there is limited appraisal of how these tools perform compared to traditional methods. To gain insight into how different methods perform in extracting data from videos taken in the field, we compared estimates of the parental provisioning rate of wild house sparrows Passer domesticus from video recordings. We compared four methods: manual annotation by experts, crowd-sourcing, automatic detection based on the open-source software DeepMeerkat, and a hybrid annotation method. We found that the data collected by the automatic method correlated with expert annotation (r = 0.62) and further show that these data are biologically meaningful as they predict brood survival. However, the automatic method produced largely biased estimates due to the detection of non-visitation events, while the crowd-sourcing and hybrid annotation produced estimates that are equivalent to expert annotation. The hybrid annotation method takes approximately 20% of annotation time compared to manual annotation, making it a more cost-effective way to collect data from videos. We provide a successful case study of how different approaches can be adopted and evaluated with a pre-existing dataset, to make informed decisions on the best way to process video datasets. If pre-existing frameworks produce biased estimates, we encourage researchers to adopt a hybrid approach of first using machine learning frameworks to preprocess videos, and then to do manual annotation to save annotation time. As open-source machine learning tools are becoming more accessible, we encourage biologists to make use of these tools to cut annotation time but still get equally accurate results without the need to develop novel algorithms from scratch.

Noise pollution, one of the most prominent features of urbanization, is an important factor influencing the vocal behavior of urban wildlife. Studies have reported that many songbirds raise their song minimum frequencies in response to urban noise. It has been proposed that this increased minimum frequency (IMF) of songs is an adaptation that allows urban populations to cope with the masking effect of noise pollution. However, urban populations of some songbirds do not exhibit significant IMF compared with non-urban populations; thus, the notion that IMF is an adaptation to urban noise has been questioned. Furthermore, the effects of IMF might be influenced by both noise levels and the acoustic structures of songs. Here, we employed dichotomous and gradient effect size approaches to investigate IMF regarding two distinct acoustic structures (whistled and harmonic) in songs of six grey-cheeked fulvetta Alcippe morrisonia morrisonia populations in Taiwan, three with high noise pollution and three with low noise pollution. We found that when using the dichotomous approach, paired populations with significant divergence in noise levels exhibited weak or insignificant divergence in the minimum frequencies for both whistled and harmonic phrases. In contrast, we found that when using the gradient approach, the effect size of noise-level divergence was strongly correlated with the effect size of divergence in the minimum frequency of the harmonic phrase and only moderately correlated with the effect size of divergence in the minimum frequency of the whistled phrase. These findings suggest that noise pollution has a more pronounced effect on the divergence in the minimum frequency of harmonic phrases used in short-range communication, compared to the whistled phrases used in long-range communication. For population comparisons on the IMF, adopting a gradient approach could provide insights into the impact of noise pollution on the acoustic structures of songs across various communication ranges.

Habitat loss and fragmentation are considered the greatest threats to ecosystems worldwide. Movement reveals how individuals meet their habitat requirements and respond to environmental heterogeneity, and thus can provide a powerful tool for investigating how animals respond to changes in landscape configuration. In our study, we examined the effects of landscape configuration on the space use and movement strategies of four endemic Hawaiian forest bird species spanning a range of foraging guilds (i.e. frugivore, nectivore, generalist). We used a landscape-level automated radio tracking system to measure location data of 127 individuals tracked on Hawaiʻi Island in a naturally fragmented landscape created by volcanic activity in the mid- to late-1800s and a nearby continuous landscape. We found that landscape configuration had a strong effect on movement patterns and space-use of all four species. In the fragmented landscape, all species predominately occupied a single forest patch, displayed a high degree of area-restricted search behavior, with few long-distance movements away from their primary forest patch. These patterns contrasted significantly with those of conspecifics in the continuous landscape which exhibited relatively unconstrained movements across the forested landscape and had 3- to 12-fold larger home ranges. Our findings indicate that landscape structure plays a strong role in shaping movement behavior of a tropical bird community and provides valuable insights into the behavioral mechanisms that may be important for species to persist within fragmented landscapes.

The question of why socially monogamous females engage in extra-pair behaviour is long-standing in evolutionary biology. Due to a lack of empirical support among passerine birds, recent work has moved away from the indirect-benefits hypothesis to explain extra-pair mating behaviour by females, instead favouring the hypothesis that this is the result of a pleiotropic effect. That is, a trait under strong positive selection in either or both sexes are genetically linked with another, potentially unrelated, trait. For example, genes beneficial to female fecundity (that promote within-pair solicitation of mating from a male partner) might also lead to extra-pair behaviour (by also promoting solicited copulations from extra-pair males). Here, we test two predictions from this hypothesis: We test the prediction that female divorce, measured as the number of social mates within a given year, is linked with 1) the number of extra-pair males engaged by the female and 2) the proportion of the female's offspring that are extra-pair. Our results show that females who divorce their social partner are more likely to produce extra-pair offspring than those who maintain social monogamy, supporting the pleiotropy hypothesis. However, those females did not also have a higher proportion of extra-pair offspring. The number of broods initiated was also positively correlated with the number of extra-pair males that sired a female's offspring, probably through increased opportunity for extra-pair males to sire offspring over a longer breeding season. Our results support the intrasexual pleiotropy hypothesis as a driver of female extra-pair behaviour.

Trans-Saharan migrants often spend a large proportion of their annual cycle wintering in the Sahel. Advances in fieldwork and tracking technology have greatly enhanced our ability to study their ecology in these areas. Using GPS-tracking we aimed to investigate the little known non-breeding movements of the lesser kestrel Falco naumanni in sub-Saharan Africa. We segment non-breeding tracks (n = 79 tracks by 54 individuals) into staging events (131 ± 25 days per non-breeding cycle), itinerant movements between staging sites (11 ± 10 days), and non-directed exploratory movements (6 ± 5 days). We then describe timing and directionality of itinerant movements by male and female kestrels throughout the non-breeding season. Regardless of sex, lesser kestrels spent on average 89% of the non-breeding season staging at two (range = 1–4) sites in West Africa. At the end of September, kestrels arrived along a broad front throughout the northern Sahel. By December, however, they congregated into two distinct clusters in Senegal and along the Malian–Mauritanian border. The birds stayed for longer periods and showed greater daily activity in the latter areas, compared to their first and intermediate ones. Among 24 individuals tracked along multiple annual cycles, 20 individuals consistently used the Senegalese or Malian–Mauritanian cluster. The remaining four birds either used these clusters in the 2nd or 3rd year of tracking or alternated between them across different years. The eastward and westward itinerant movements of lesser kestrels during the non-breeding season, coupled with their tendency to cluster geographically towards the end, differ from the southward movements of other insectivorous raptors in West Africa. While 31% of Spanish lesser kestrels converged in Senegal, where roosts of > 20 000 birds are known, 68% moved into the Malian-Mauritanian border region where more groundwork is needed.

Sperm traits are important in determining fertilisation success and are metabolically expensive to produce. There is little known about how energy acquisition and allocation affect sperm traits in avian taxa. This study assesses the impact of experimentally manipulated diet on long-tailed finch sperm by comparing the length of sperm components (head, midpiece, flagellum and total sperm) between the treatment groups (homogenous diet and diverse diet) and across time points (before and after the experiment). Diet homogeneity was manipulated as this may impact diet quality in a species that is usually fed a diversity of seed species to thrive in captivity. Our results showed no impact of diet on the length of different sperm components. These results contrast with findings of a similar recent study of the zebra finch which found a significant level of diet-affected plasticity in midpiece length. For both diet treatment groups in this study there was a slight but significant increase in head, flagellum and total sperm length over the treatment period. Despite this, all sperm components were highly repeatable, consistent with the finding from observational studies in passerine birds. The efficacy of our dietary manipulation was confirmed by a significant reduction in the saturation of bill colour in the long-tailed finches as a result of the homogenous diet, and a difference in body mass across the treatment groups.

Seabirds within the Alcini subfamily have a unique breeding strategy, with their offspring leaving the colony flightless, at only a quarter of adult body size, accompanied by the father and fledge (become independent) out at sea. In this study we test several hypotheses about this elusive second part of the breeding season, termed swimming migration, for common guillemots Uria aalge and Brünnich's guillemots Uria lomvia by tracking 34 chicks (of which 17 transmitted data) equipped with satellite linked Argos PTTs (Platform Transmitter Terminals) at Bjørnøya, a major colony in the European Arctic. All chicks, presumably accompanied by their fathers, swam actively towards species-specific autumn staging areas, rather than passively drifted away from the colony with a swim speed generally twice that observed of surrounding surface currents. They swam fastest during the first two days after departure. This coincides with the only time they actively crossed a current and the time needed to leave the area of prey depletion around the colony. They otherwise took advantage of available currents, while still swimming actively during the remainder of their migration towards species-specific autumn staging areas. These staging areas corresponded to areas used by breeding adults during their moulting period (as confirmed by complementary light-level logger tracking of adults), rather than being specific nursery areas. Migration duration correlated with distance resulting in species-specific migration periods that were only a fraction of previously reported fledging periods out at sea, indicating that not only the swimming migration, but also known adult autumn staging regions constitute in effect breeding areas. This work has important implications for our understanding of population dynamics within the Alcini subfamily and the management of these species under multiple threats, while providing the foundation to investigate swimming migrations across their distributional range.