Ibis最新文献

Studies of the response of high-trophic-level predatory species to environmental gradients contribute to our understanding of adaptation, dependency and risk, both to the predator and its prey. Many such species are of high conservation concern because of a slow life history and a greater susceptibility to threats, not least in organized anthropogenic landscapes that have the propensity to modify or even distort predator–prey dynamics. There are, however, observational difficulties in studying species that are wide-ranging and furtive in their behaviour. All the above characteristics are shared by the Eurasian Goshawk Accipiter gentilis, a highly elusive species for which the movements and habitat associations are poorly quantified at large geographical scales. In Great Britain, this species is of further interest because the population is recovering from the historical impacts of persecution. Here we used remote tracking methods to gather spatially accurate accumulations of data for reliable depictions of movement scale and habitat use in Eurasian Goshawks during the early months of independence from the nest environment (termed ‘first-winter’). The data were taken from two regions of England for good geographical representation of lowland habitats. First-winter Eurasian Goshawks exhibited strongly philopatric characteristics with low levels of natal dispersal once settled. They adopted sedentary and localized foraging patterns, averaging less than 5 km in diameter for approximately 90% of the time, located on the periphery of breeding habitat and centred on farmland or farmland edge, unlike the more forest-centric adults. The use of farmland was especially the case for the first-winter males compared with females, which we speculate may be driven by competitive exclusion or hunting advantages. The results are discussed in the context of future population recovery and colonization, while recognizing existing and emerging threats, including diseases such as highly pathogenic avian influenza and trichomonosis. The study also serves as a methodological demonstration of the capacity for tracking technology to contribute more to our understanding of predators and, by extension, predation as a response to change (such as land-use practice), that can shape observed patterns of conflict.

Black-tailed Godwit Limosa limosa limosa clutches have been collected for headstarting, a captive rearing intervention where eggs are taken from the wild and artificially incubated, and chicks are reared in captivity to fledging, before being released into the wild. This conservation measure has reduced local extinction risk for the UK population, but it may have impacts on genetic diversity and population viability, especially when wild-sourced eggs must be collected from a small population. Comparing the UK population of 42 pairs with the much larger breeding population in the Netherlands (~30 000 pairs), we found that levels of heterozygosity and inbreeding are not currently compromised, and allelic richness in the UK population was not significantly different from the Dutch population, but relatedness estimates suggest that 6.1% of the individuals in the UK are closely related, at the level of half-sibling and up, compared with 1.9% in the Dutch population. Increasing levels of relatedness could further deplete genetic variation, in the absence of immigration or the introduction of wild-sourced eggs from other populations.

Ecological theory predicts that coexisting species should exhibit realized niche differentiation to minimize competition. However, little is known about patterns of niche differentiation when ‘newcomer’ species spontaneously colonize a new region, leading to novel sympatric conditions. Over the past 15 years, three closely related and ecologically similar falcon species (Common Kestrel Falco tinnunculus, Lesser Kestrel Falco naumanni and Red-footed Falcon Falco vespertinus) have expanded their ranges as the result of land-use and climate changes in the intensively cultivated agroecosystems of the Po Plain (Northern Italy). This is a unique condition in the European range of these species and provides an excellent opportunity to investigate patterns of foraging and trophic niche partitioning during the initial phases of sympatry. We assessed species-specific patterns of foraging habitat selection and interspecific differences in diet composition. Our findings showed that falcons selected largely overlapping foraging habitats, yet exhibited significant differentiation among species regarding vegetation height, structure and crop types. Overall, diet composition was similar, though some degree of trophic niche differentiation was detected. In line with the niche partitioning hypothesis, the three species slightly partitioned their foraging and trophic niches, probably playing a key role in making syntopic coexistence possible. Our study provides insights into the mechanisms of niche partitioning when ‘newcomers’ appear in a guild, a process that is likely to become increasingly relevant because of the rapid and often uneven distributional shifts caused by global change.

The ability to meet the high energetic costs of long-distance migration can be a key factor in the survival of individual birds. The use of stopovers, where individuals pause to rest and feed, is a common strategy in many migratory bird species. In this study, we explore migration timing of 28 satellite-tracked (17 GPS and 11 Argos) adult migratory Ospreys Pandion haliaetus from northeastern Germany. For 15 of the GPS-tracked birds that migrated to Africa, we used Generalized Linear Mixed-effects Models to analyse the effects of sex, migration period, departure date and other factors on the number of stopovers per season, and the individual and total lengths of stay at stopover sites. Female long-distance migrants arrived at breeding sites earlier than male long-distance migrants in spring, contradicting common theory. Females left the breeding sites on autumn migration more than a month before males. The number of stopovers was not affected by the variables tested, but more stopovers led to longer total stays per individual migration period. Autumn stopovers were longer in total (males: mean = 58.1 h (95% CI = 31.1–85.0); females: mean = 164.0 (98.3–229.6)) than spring stopovers (males: mean = 50.9 h (0.0–114.6); females: mean = 39.9 (11.9–67.9), especially with early autumn departure dates. Ospreys spent long periods at stopovers mainly at high latitudes (in Europe), but relatively long stopovers were also observed in North Africa (between the Mediterranean and the Sahara), so stopover length did not vary with latitude. Seasonal fidelity to stopover sites between years was low, except for five females. This flexibility complicates the establishment of protected areas for migrating Ospreys along the migratory flyway.

The Great Plains contains many contact zones between eastern and western North American bird species. In these contact zones, closely related lineages or species vary widely in both the geographical and the genomic extent of their hybridization. Two phenotypically similar sister species of flycatchers – the Eastern Wood-Pewee Contopus virens and the Western Wood-Pewee Contopus sordidulus – have sparse geographical overlap in the Great Plains, including a few isolated planted forest stands and along forested riparian corridors of the Niobrara and Platte rivers in central Nebraska, USA. Our previous genetic work found low levels of genetic differentiation between these two flycatcher species, along with several putatively admixed individuals in this zone of sympatry in Nebraska. Here, we used whole-genome sequencing to confirm the presence of admixed individuals and quantify nonrandom gene flow, both in direction between taxa and location in the genome. We confirm the presence of both early-generation hybrids and highly backcrossed individuals in this contact zone. We found moderate levels of genetic differentiation between the two species, with the highest differentiation on the Z chromosome. In addition, all individuals in sympatry contained at least some minor parental genomic ancestry, suggestive of bidirectional introgression. There was evidence of introgression in sympatric individuals across the entire genome, except for approximately half the Z chromosome, suggesting that there is some selection and resistance to admixture in this genomic region.

Our understanding of the functional importance of olfaction to birds has improved over the past 60 years, largely as the result of experimental studies testing how birds use their sense of smell in different contexts. As it is impossible to measure directly which odours birds can detect, we rely on measuring behavioural responses to scent cues or manipulations which diminish their olfactory acuity. Here, we review the findings of these studies structured by when and how birds used their sense of smell: during foraging, navigation, social interactions with con- or hetero-specifics, nesting or for predator detection. Most studies investigated how birds use their olfactory sense during foraging (n = 52) and nesting (n = 42), but fewer examined how birds use olfaction during social interactions (n = 38), navigation (n = 20) or predator recognition (n = 21). Knowledge is mainly restricted to certain Orders (e.g. Procellariiformes). Although the diversity of neuroanatomical and molecular structures underlying olfaction suggests that olfactory acuity varies considerably among extant bird species, an understanding of which ecological factors drive selection for olfactory acuity in birds is mostly lacking. How experiences expand a bird's chemosensory knowledge over time and whether birds can learn to recognize odours associated with foraging opportunities or danger from predators is still poorly understood. Finally, there is a lack of knowledge about how long some volatiles remain useful to birds before they have decayed, and which volatiles, or combinations of volatiles, contained within some olfactory cues are being detected by birds. We encourage ornithologists to tackle these broader questions to better understand the functional importance of olfaction to birds.

Moult is an essential part of birds' annual cycle, and requires sufficient intake of energy and nutrients, but we understand little about how such nutritional requirements are met by wild birds. Using faecal metabarcoding, we analysed the diet of moulting and non-moulting Common Bulbuls Pycnonotus barbatus, captured in Cameroon. We found that the diet of moulting birds was more diverse than that of non-moulting birds, with approximately 1.5 times more arthropod and plant taxa, plus evidence of dietary composition differences between groups. Our results provide novel insight of a likely strategy used by wild birds to fuel the essential self-maintenance task of moult.

Ornithologists use many methods to advance understanding of birds and inform conservation strategies. These include field methods (e.g. censusing, ringing), laboratory analysis (e.g. molecular taxonomy, microbiology) and computational approaches (e.g. population modelling, habitat suitability mapping). Indirect metrics can also be important: for example, ptilochronology as a proxy for food availability and dominance hierarchies, stable isotopes as a proxy for diet and first egg dates as a proxy for phenological responses to climate change. Recently, the potential to use palynology – the study of pollen and spores – in ecology has become increasingly recognized, but there has been no specific appraisal of the utility of palynology in ornithology. In this scoping review, we synthesize research undertaken over 70 years across all seven continents covering the many diverse ways in which studying pollen associated with birds can advance ornithological understanding and inform conservation strategies. We critique the use of palynology both directly and as a proxy to study avian habitat use, migration ecology, diet and feeding strategies, and population dynamics, offering constructive suggestions for future research at the end of each thematic section. We also explore the potential for analysing pollen on birds (or within avian deposits such as guano) to answer wider questions, especially in relation to pollination and environmental reconstruction, thereby offering cross-disciplinary collaborative research ideas. We conclude that the potential for uniting ornithology and palynology within the research and conservation contexts is as extensive as it is exciting and urge avian biologists to think broadly about new opportunities.

Cooperative breeding in birds is thought to be more common in altricial species, with few described cases in precocial species. However, cooperative breeding may also be more difficult to detect in precocial species and could have been overlooked. We investigated whether precocial Vulturine Guineafowl Acryllium vulturinum breed cooperatively and, if so, how care is distributed among group members. We collected data from 51 uniquely marked individuals (27 males, 24 females), of which 13 females bred at least once over three different breeding seasons. We found that broods had close associates comprising both adults and subadults that exhibited four distinct cooperative breeding behaviours: babysitting, chick guarding, covering the chicks and calling the chicks to food. Further, we found that offspring care is significantly male-biased, that non-mother individuals provided most of the care that each brood received, that breeding females differed in how much help they received and that carers pay a foraging cost when providing care. In line with many other birds, we found that females received help from their sons. Our results confirm that Vulturine Guineafowl are cooperative and plural breeders and add to growing evidence that cooperative breeding may be more widespread among species with precocial young than previously thought, thereby providing a counterpoint to the altriciality–cooperative breeding hypothesis.

The post-fledging dependence period (PFDP) is a fundamental stage in the life cycle of altricial birds that influences their long-term survival and fitness. However, research on the duration of this period in raptors, and on the factors affecting it, is scarce. We performed the first literature review on the length of the PFDP in Accipitridae, the largest family among diurnal raptors, and a meta-analysis examining the effects of breeding latitude and hemisphere, body weight and migratory status, controlling for species phylogeny. Hypotheses were tested at the levels of both species and populations. The length of the PFDP is known for less than half of Accipitridae species, with no data for two-thirds of the threatened and near-threatened species. Larger species and individuals breeding at lower latitudes showed a longer PFDP, as did non-migrants and southern-hemisphere breeders. The effect of latitude was more marked in larger species, in resident populations and in southern-hemisphere breeders. This extended PFDP in larger and tropical raptors may promote juvenile survival. Migration timing and the effects of continentality in the northern hemisphere constrain the PFDP. These findings highlight the importance of encouraging the study of this key, but poorly known, life-cycle stage of raptors.