Journal of Avian Biology最新文献

Behaviors associated with breeding can increase mortality risk. This increased risk can be thought of as a cost of reproduction. Increased movements prior to breeding are common as individuals search for food and breeding sites. These increased movements are thought to entail greater predation risks as individuals travel through unfamiliar areas but few studies have looked at how these prebreeding movements affect survival, especially at a fine temporal resolution. Costs of reproduction may also occur during reproduction. For birds, incubation and brood-rearing can increase predation risk because individuals spend most of their time at nest sites or with broods, which may make them more easily detected and captured by predators. Using time- and individual-specific predictors of survival, I examined the relationship between survival, movements, habitat use and breeding status of northern bobwhites Colinus virginianus in Colorado, USA. I found that prebreeding ranges were larger for breeders (29 ha) than non-breeders (18.7 ha) but daily movement distance was not different (163 m). Range size did not affect survival; however, longer recent daily movement distances (within 10 days) resulted in higher survival. Breeding status also affected survival; laying individuals experienced the highest daily survival rates followed by incubating, non-breeding and brood-rearing individuals. Overall, there appears to be a survival cost of reproduction for individuals during brood-rearing, but I found no evidence that increased movements results in decreased survival.

Gut microbiota are increasingly recognized as important drivers of host health and fitness across vertebrate taxa. Given that gut microbial composition is directly influenced by the environment, gut microbiota may also serve as an eco-physiological mechanism connecting host ecology, such as diet, and physiology. Although gut microbiota have been well-studied in mammalian systems, little is known about how gut microbial diversity and composition impact morphological and physiological development in wild birds. Here, we characterized both diet and gut microbial diversity of free-living American kestrel Falco sparverius nestlings throughout development to test whether gut microbial diversity predicts host morphological and physiological traits in either contemporary or time-lagged manners. Gut microbial alpha diversity on day 21 of nestling development was positively correlated with diet alpha diversity representative of the majority of nestling development (days 5–20). Gut microbial alpha diversity early in development was negatively correlated with body mass in both contemporary and time-lagged manners. Gut microbial alpha diversity early in development was positively correlated with blood glucose later in development. As nestlings experience rapid growth demands in preparation to fledge, these time-lagged associations may indicate that gut microbial diversity at early critical developmental windows may determine the future trajectory of morphological and physiological traits underlying metabolism that ultimately impact fitness.

The knowledge of migratory connectivity is important for understanding the potential drivers of populations and it is thus important for conservation implications. Migratory connectivity of species can be studied using exogenous, such as rings and transmitters, or endogenous markers, such as stable isotopes and trace elements. The use of trace elements has been much less frequently studied compared to stable isotopes. Trace elements can be studied from the feathers of birds and this does not necessarily require trapping of individuals. Here we studied the variation of 18 different trace elements in feathers of two long-distance trans-African migrants, willow warblers Phylloscopus trochilus and barn swallows Hirundo rustica, using body feathers of museum specimens of birds from Finnish breeding grounds. The trace elements were measured using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS). We show that trace element concentrations were relatively stable along the rachis within the same feather except in Ni and S, which showed a quadratic pattern. In general, variation within feathers of the same individuals was smaller than in feathers between individuals for most elements. Furthermore, concentrations of 11 trace elements showed significantly higher concentrations in willow warbler feathers collected in spring than in autumn, moulted in African wintering grounds and European breeding grounds, respectively. Last, concentrations of seven trace elements were significantly higher in the spring feathers of willow warblers compared to barn swallows. This suggests that trace elements could be used to separate moulting grounds of the birds on the larger scale within the same species, but also sampling design should be carefully considered.

The Arctic Coastal Plain is one of the most important avian breeding grounds in the world; however, many species are in decline. Arctic-breeding birds contend with short breeding seasons, harsh climatic conditions, and now, rapidly changing, variable, and unpredictable environmental conditions caused by climate change. Additionally, those breeding in industrial areas may be impacted by human activities. It is difficult to separate the impacts of industrial development and climate change; however, long-term datasets can help show patterns over time. We evaluated factors influencing reproductive parameters of breeding birds at Prudhoe Bay, Alaska, 2003–2019, by monitoring 1265 shorebird nests, 378 passerine nests, and 231 waterfowl nests. We found that nest survival decreased significantly nearer high-use infrastructure for all guilds. Temporally, passerine nest survival declined across the 17 years of the study, while there was no significant evidence of change in their nest density. Shorebird nest survival did not vary significantly across years, nor did nest density. Waterfowl nest density increased over the course of the study, but we could not estimate nest survival in all years. Egg predator populations varied across time; numbers of gulls and ravens increased in the oilfields 2003–2019, while Arctic fox decreased, and jaeger numbers did not vary significantly. Long-term datasets are rare in the Arctic, but they are crucial for understanding impacts to breeding birds from both climate change and increasing anthropogenic activities. We show that nest survival was lower for birds nesting closer to high-use infrastructure in Arctic Alaska, which was not detected in earlier, shorter-term studies. Additionally, we show that Lapland longspur nest survival decreased across time, in concert with continent-wide declines in many passerine species. The urgency to understand these relationships cannot be expressed strongly enough, given change is continuing to happen and the potential impacts are large.

Reliable estimates of adult survival for many shorebird species are lacking. We used Cormack–Jolly–Seber (CJS) methods to provide an estimate of apparent, or local, survival (φ) of a population of whimbrels, Numenius phaeopus, breeding in the subarctic Churchill, Manitoba region. We used data collected in two time-periods: 1973–1976 and 2010–2014. We also quantified nest-site fidelity in 2010–2014 to provide context to our apparent survival estimates because mark-recapture analyses cannot distinguish between mortality and permanent emigration. The most parsimonious CJS model did not include effects of sex or time on apparent adult survival in either period (φ = 0.76 ± 0.13 SE; φ = 0.75 ± 0.04 SE, 1973–1976 and 2010–2014, respectively). Additionally, observations of marked whimbrels between 2010 and 2019 (n = 124) showed that 61 of the 105 marked individuals (58.1%) were resighted. These estimates of return rates are, as expected, much lower than estimates of apparent survival. The median year-to-year distance between nests (n = 139) in 2010 to 2014 was 198 m ± 88 SE and did not differ significantly (p = 0.84) between females (x̄ = 721.9 m ± 119.8 SE) and males (x̄ = 720.3 m ± 83.1 SE). If our apparent survival estimate is indicative of true survivorship, then adult mortality during the non-breeding season has remained constant over the last five decades, implying that the recent decline in whimbrel populations may stem largely from reduced fecundity, including egg or juvenile survival, rather than primarily from reduced adult survival.

Variation in developmental conditions is known to affect fitness in later life, but the mechanisms underlying this relationship remain elusive. We previously found in jackdaws Corvus monedula that larger eggs resulted in larger nestlings up to fledging. Through a cross-foster experiment of complete clutches we tested whether this association can be attributed to egg size per se, or to more proficient parents producing larger eggs and larger nestlings, with the latter effect being more or less independent of egg size. Due to other manipulations post-hatching, we primarily investigated effects on nestling mass on day 5, which we show to predict survival until fledging. We introduce a new statistical approach to compare the competing hypotheses and discuss the multiple advantages of this approach over current practice of which we report the results for comparison. We conclude that 92% of the slope of the association between egg size and nestling mass can be attributed to a direct effect of egg size. The remaining 8% of the slope can be attributed to aspects of parental chick rearing ability as reflected in egg size, but this component did not deviate significantly from zero. Intriguingly, the effect of egg size on day 5 nestling mass was steeper (1.7 g cm⁻³) than the effect of egg size on day 1 hatchling mass (0.7 g cm⁻³). Early growth is exponential, and the difference in effect size may therefore be explained by hatchlings from large eggs being further in their development at hatching. The direct effect of egg size on nestling mass raises the question what causes egg size variation in jackdaws.

Sex ratio theory suggests that females should bias offspring sex ratios based on maternal condition and the availability of critical food resources. Work in birds indicates that females do, indeed, bias sex ratios according to maternal condition and food quality and quantity. Yet it is unknown whether these sex ratio skews occur due to fluctuations in particular micro- or macro-nutrients, caloric content overall or even the perception of food availability. We hypothesized that dietary fats may drive biases in offspring sex ratios, because measures of maternal condition often reflect fat reserves, and fats are critical for the process of egg-laying in birds. To test this, we provided breeding Japanese quail, a species that biases sex ratios in response to maternal condition, with either a control breeding diet or a diet supplemented with two oils (safflower oil and flaxseed oil). These oils were chosen for their high omega-3 and omega-6 fatty acid content as well as their importance in mammalian sex allocation. We then measured influences of these diets on the sex ratio of offspring, the change in maternal weight, and the laying rates of female quail. The dietary oil supplements increased weight gains in quail but decreased the number of eggs laid during the experiment. There was no influence of the oil supplements on offspring sex ratios. This indicates that fat may not be a macro-nutrient involved in the process of sex ratio adjustment in quail.

The reed bunting, Emberiza schoeniclus (Linnaeus 1758), is the only member of the genus adapted to Mediterranean wetlands, where some subspecies are critically endangered. The first complete mitogenome of the eastern Iberian reed bunting (E. s. witherbyi) is presented here and compared with an unpublished mitogenome obtained in northeast Asia (most likely E. s. pyrrhulina). Genetic distance analyses are consistent with the new reed bunting data corresponding to two distinct lineages of E. schoeniclus. A new fossil-calibrated phylogeny suggests that open forest buntings have suffered two rapid speciation events from Late Miocene to Pleistocene, that seem to be correlated with major climatic changes and habitat shifts. Adaptation to a new ecological niche (i.e. wetlands) could have favoured the reed bunting expansion across the Palearctic. The high intraspecific variation observed today could result from the establishment of resident populations within small areas, potentially acting as a climatic refuge.

The non-breeding season presents significant energetic challenges to birds that breed in temperate or polar regions, with clear implications for population dynamics. In seabirds, the environmental conditions at non-breeding sites drive food availability and the energetic cost of regulatory processes, resulting in variation in diet, behaviour and energetics; however, very few studies have attempted to understand if and how these aspects vary between populations. We investigated whether non-breeding location influenced diet, behaviour and energetics in the common guillemot Uria aalge. We studied guillemots from four UK breeding colonies, two located on the west coast of Scotland and two on the east. We quantified non-breeding distribution, foraging behaviour and activity budgets of 39 individuals from July to March, using geolocation–immersion loggers and time-depth recorders, and used feather stable isotope signatures to infer diet during the post-breeding moult. We calculated energy expenditure and investigated whether the peak (an indicator of the potential vulnerability to marine threats) varied between colonies. Individuals were spatially segregated according to the coastline they breed on, with west coast guillemots distributed off the west coast of the UK and east coast guillemots distributed off the east coast. Diet and behaviour were more similar in guillemots that shared a breeding coastline than those that did not, as west coast guillemots foraged at a lower trophic level, spent less time diving and engaged in more pelagic foraging than east coast guillemots. However, energy expenditure was remarkably similar between colonies, peaking during late February/early March, indicating that, during our study period, there was high synchrony between colonies in the timing of potential vulnerability to marine threats. Therefore, any anthropogenic changes that result in decreased food availability or increased energy expenditure during late winter may have greater impacts on energy balance, with consequences for population dynamics.

Migratory birds typically separate energetically demanding parts of the annual cycle like breeding, moult and migration with some species engaging in so-called moult-migration. Moult-migration is known to occur in starlings from the northern breeding populations, however, little is known about the dynamics of this phenomenon and the costs and benefits for the involved individuals. Here, using state-of-the art multi-sensor geolocators we gathered information about the annual cycles of 10 starlings from two breeding sites in Latvia. We used a novel analytical approach based on atmospheric pressure measurements to reveal that all but one of the tracked individuals migrated to wintering sites in the British Isles. Tracking data exposed two separate migration strategies – 1) departure from the breeding grounds in mid-June soon after chick fledging with long stationary periods at moulting sites approx. 900 km westward (n = 5 of 10); 2) residing in close vicinity of the breeding sites up until the end of October (n = 5 of 10). Accelerometer data revealed significantly higher activity budgets during moult for the individuals exhibiting moult-migration. Furthermore, birds that underwent moult-migration arrived at the breeding sites in the following year on average 10 days later and showed significantly higher activity levels during the pre-breeding period compared to birds without moult-migration. Activity tracking also showed that 67% of all migratory flights were performed during the night, contradicting previous assumptions of starlings being predominantly diurnal migrants. Maximum recorded flight altitudes reached 2500 m a.s.l. and the longest uninterrupted flight lasted 22.5 h. Our results highlight energetic trade-offs of moult-migration in starling, but their downstream consequences remain to be tested.