Ibis最新文献

Species distributions are often indicative of historical biogeographical events and contemporary spatial biodiversity patterns. The Harlequin Duck Histrionicus histrionicus is a sea duck of conservation concern that has a disjunct distribution, with discrete portions of its range associated with northern Pacific and Atlantic Ocean basins. Movement data indicate migratory connectivity within regions of each ocean basin but not cross-continent dispersal, suggesting that genetic structuring could exist at multiple spatial scales. Little is known regarding the impacts of past vicariance events on the species phylogeographical structure and historical demography, or rates of gene flow at different spatial scales. We used data from microsatellite loci and mitochondrial DNA (mtDNA) sequences to quantify levels of genetic diversity within, and the extent of spatial genetic differentiation among locations sampled at multiple spatial scales across the species range. Samples were collected at nonbreeding locations, which represent groupings appropriate for characterizing genetically differentiated subgroups at regional and continental scales. Collectively, genetic data and coalescence modelling suggested that individuals colonized regions currently occupied within both ocean basins in the Holocene from a single refuge in the Atlantic. Further, it seems likely there was secondary contact with lineages derived from populations in Asia, based on the shallow species-wide mtDNA phylogeny and high incidence of recently derived private mtDNA haplotypes. Estimates of inter-location variance in microsatellite allele and mtDNA haplotype frequency were moderate and significant between western (Pacific – North America) and eastern (Atlantic – North America, Greenland and Iceland) ocean basins and among sampling groups within each ocean basin. Genetic differentiation among sampling groups was particularly evident at the species distributional margins in the Atlantic (Iceland) and the Pacific (Shemya Island) Ocean basins. Coalescent modelling results suggest that contemporary spatial genetic patterns in the species arose through the combined influences of secondary contact, shared ancestry and gene flow after the last glacial maxima.

Assessing habitat quality is critical for migrating birds, with implications for fuel loading, predation risk and timing of departure. To efficiently distribute within stopover sites, migrants rely on various cues that facilitate habitat quality assessment. In this study, we conducted a playback experiment at a mid-route stopover site to test the effects of vocal cues, specifically bird songs, on habitat redistribution during spring migration. To estimate the effect of bird songs on bird abundance we mist-netted and ringed birds for 60 days on alternating playback treatment (playing songs of three sylviid warbler species) and no playback (control) days. A nearby site was used to control for fluctuations caused by migration waves. Overall, total bird abundance was significantly increased by the playback treatment. This increase resulted from the attraction of conspecifics (species whose songs were played) rather than of other species – sylviids or others. Correspondingly, species richness was seemingly unaffected. To investigate the relationship between internal-state factors and the attraction to playback in the most abundantly attracted species, Eurasian Blackcap Sylvia atricapilla, we tested associations with age, sex and body condition index but found no significant effects, possibly because of the limited sample size. Our findings challenge established ideas regarding heterospecific attraction and contradict previous studies. Attraction to bird song is discussed in the context of geographical location, timing and internal drivers. Vocal cues, specifically bird songs, may affect micro-habitat selection by migrating songbirds during stopovers. Consequently, we call for consideration of the influence of the acoustic environment on birds during migratory stopover in future studies, habitat management and conservation efforts.

The over-exploitation of wild birds and the products derived from them can be a key threat driving changes in bird species richness and abundance. However, inadequate information on harvest levels combined with irregular population monitoring often means that the role of harvesting in population decline is difficult to quantify. Historically, the pan-tropical Sooty Tern Onychoprion fuscatus has been subjected to extensive egg harvesting, yet the role of sustained harvesting in population change and future population viability remains unclear. In this study, we used published and new estimates of key demographic rates for a large, harvested Sooty Tern population in Seychelles, western Indian Ocean, to run a series of population viability analyses. We retrospectively assess the impact of historical levels of egg harvesting, and also predict how this population may respond under different future harvesting regimes, assuming no additional environmental change. We provide evidence that egg harvesting has played a substantial role in driving the population decline of Sooty Terns to date and demonstrate that continued harvesting will probably lead to further, possibly dramatic, declines in population size. These results indicate that recent levels of egg harvesting in Seychelles are not sustainable. We also show that the life-history strategy of Sooty Terns, including a delayed age of first breeding, means the current 2-year local moratorium on egg harvesting is unlikely to generate an observable population-level response in Seychelles. Instead, we recommend that the current moratorium is extended at least beyond the age of first breeding (i.e. 5 years) to support appropriate evaluation. We additionally show that harvesting Sooty Tern eggs at much lower levels, i.e. 10% of the population size, is unlikely to reverse population decline. Therefore, long-term egg harvesting strategies require careful evaluation to maintain a balance between the social, commercial, cultural and biodiversity significance of Sooty Terns in Seychelles.

Irruptions by boreal seed-eating and frugivorous birds are assumed to be driven by the production of seeds and fruits, crops of which are highly variable between years. Using data from Sweden, we tested whether irruptions of Common Crossbills Loxia curvirostra were correlated with low Norway Spruce Picea abies seed production in the same year as the irruption and/or high seed production in the year prior to an irruption. Similar tests were made for Parrot Crossbill Loxia pytyopsittacus irruptions in relation to Scots Pine Pinus sylvestris seed production. In northern Europe, these conifers represent the key food species of the two crossbill species, respectively. Despite differing times that seeds take to mature and asynchronous seed production between the two conifer species, including a 3-year cycle for Norway Spruce, the two crossbill species often irrupted in the same year as one another. Analyses showed that irruptions into Britain and other parts of western Europe by both crossbill species were correlated with low seed production by Norway Spruce in Sweden. Low seed production by Scots Pine had a marginally non-significant additive effect on both crossbill species. In a second set of analyses, the best-fitting model was one in which low seed production by both conifers in a given year and high seed production in the previous year were each correlated with large numbers of irrupting Common and Parrot Crossbills. The models indicate that the incidental co-occurrence of low seed production of Norway Spruce and Scots Pine in a given year, after a year of high seed production, may result in an irruption. The seed production of Norway Spruce and Scots Pine in Sweden was correlated with production by the same species in Finland, indicating widespread synchrony of cropping across northern Europe.

Understanding how diverse assemblages of scavengers can coexist on shared ecological resources is a fundamental challenge in community ecology. However, current approaches typically focus on behaviour at carcass provisioning sites, missing how important differences in movement behaviour and foraging strategies can facilitate sympatric species coexistence. Such information is particularly important for vultures – obligate scavengers representing the most endangered avian foraging guild. Their loss from ecosystems can trigger trophic cascades, mesopredator release and disease outbreaks. We provide the first-ever analyses of GPS location data from wild King Vultures Sarcoramphus papa and Greater Yellow-headed Vultures Cathartes melambrotus, coupled with trait data (from both wild-living and museum specimens) and visitation data from camera traps deployed at provisioned carcasses, to characterize vulture flight behaviour and strategies in the Peruvian Amazon. We found marked species differences in several key movement characteristics, including: King Vultures having home-ranges five times larger, average flight heights four times greater and ground speeds 40% faster than those of Greater Yellow-headed Vultures. Despite these differences, both species flew similar distances each day (on average), probably due to King Vultures taking 50% fewer flights and spending 40% less time in the air per day. Consistent with these patterns, King Vulture body mass was more than double that of the Greater Yellow-headed Vulture, with a substantially larger hang wing index (a measure of long-distance flight efficiency). At carcasses, Greater Yellow-headed Vultures typically arrived first but were rapidly outnumbered by both King and Black Vultures Coragyps atratus. We find that the movement behaviour of obligate apex scavengers in the western Amazon is linked to their ability to coexist – Greater Yellow-headed Vultures, a smaller stature ‘scouting’ species adapted to fly low, forage early and arrive first at carcasses, are ultimately displaced by larger-bodied, wider ranging King Vultures at large ephemeral carrion resources. Expansion of future GPS tracking initiatives could facilitate the exploration of direct facultative interactions from animal movement data and give further insight into how diverse communities assemble and interact.

Societies are all about people. People join them to meet other people with shared interests. Some people go on to help run the society, to help deliver the activities and services that members want. And some people embed themselves within a society, quite often going unnoticed, becoming part of the fabric that gives a society their place, their identity. The Janet Kear Union Medal celebrates such people.

If you look back through BOU annual reports from the mid-2000s onwards, one of the most frequently mentioned and thanked members is Dr Helen Baker. Already an engaged member and conference attendee, Helen began her 14-year stay on BOU committees and Council when she joined the Meetings Committee in 2008. This was an ideal starting point for Helen to operate from ‘within’ the BOU, having already contributed to various conference scientific committees and working groups, by putting her first-hand event experience to great use and delivering an important science and conservation policy angle to many conferences.

In 2013 Helen was elected as an Ordinary member of Council as the pre-cursor to being elected Honorary Secretary in 2014, a position she served for two terms until 2022. As ‘Hon Sec’ Helen joined the BOU's Management Group and took a hands-on role in managing and supporting the Union's two permanent staff. She helped to further develop and undertake the annual staff reviews, ensuring that staff were fully supported in their roles in delivering across all BOU activities, a contribution which also enabled her to have critical oversight of all that the Union delivered. During this time, she built a strong relationship with Chief Operations Officer, Steve Dudley, and with both being Peterborough-based, Helen was able to provide Steve with much-needed face-to-face mentoring and support in his key role of running the BOU as a remote worker.

On arriving on Council in 2013, Helen championed the BOU's recent take-up of social media, particularly Twitter, to not just promote and drive BOU activities, but to be a unifying voice for ornithology and the drive to build an actively engaged online community. More than many at the time, Helen recognized that for a small society with a global membership, social media overcame a previous inability to engage with both members and the wider ornithological community much more regularly and effectively. Such a strong voice of support was not just critical around the Council table but more importantly it helped to drive the BOU's aim of establishing the Union as a truly global society both on- and off-line.

Helen was also a staunch supporter of the BOU widening its equality and diversity commitments, taking the Union's work beyond gender issues by making the BOU a welcoming society for all those working in ornithology, including giving LBGTQ+ ornithologists a louder presence and voice via the BOU Rainbow Blog, the establishment of the BOU's Equality and Diversity Working Group and the dev

Population responses to environmental changes can often vary geographically and between environments, potentially as a consequence of differing niche dynamics. The Eurasian Skylark Alauda arvensis is an open-habitat passerine bird that is declining throughout Europe, mainly due to agricultural intensification. We compared population trends (1992–2021) of the species across three sub-regions of northern Italy characterized by different environmental conditions and human pressures: the Alpine sub-region (less anthropized mountains), the Plain (strongly anthropized and intensively cultivated) and the Oltrepò (less intensively cultivated hills), with changes in the realized Grinnellian niches over three decades. In each sub-region, niche comparisons did not show divergence over the study. However, we found an overall reduction in niche occupancy over time. In the Alpine sub-region, a reduction in niche occupancy in hayfields and pastures was not associated with population decline; indeed, we found an increasing population (+164%), probably because high availability of natural grasslands counteracted niche contraction. Conversely, in the Plain and Oltrepò sub-regions, the observed population declines (−99% and −36%, respectively) are associated with a general reduction of niche occupancy in arable lands that represented the core of the niche in these ranges. In the Plain, the lack of alternative suitable habitats might have limited any opportunity for the species to colonize new environments. Conversely, in the Oltrepò, the less severe population decline is combined with increased niche occupancy in hayfields and pastures at higher elevations. The joint application of population trend analysis and niche modelling as well as the decomposition of population changes across different environmental contexts can contribute to a better understanding of ecological processes affecting population dynamics, supporting policy-makers to implement targeted conservation strategies.

We describe new specimens and species of apodiform birds from the early Eocene London Clay of Walton-on-the Naze (Essex, UK). In addition to multiple partial skeletons of Eocypselus vincenti Harrison, 1984, three new species of Eocypselus are described as Eocypselus geminus, sp. nov., Eocypselus paulomajor, sp. nov. and Eocypselus grandissimus, sp. nov. The previously unknown quadrate of Eocypselus shares a characteristic derived morphology with the quadrate of the Aegothelidae, Hemiprocnidae and Apodidae, whereas the quadrate of the Trochilidae is very different. We also report a striking disparity of the shapes of the axis vertebra of apodiform birds, which is likely to be of functional significance. Eocypselus and extant Hemiprocnidae and Cypseloidini (Apodidae) exhibit the plesiomorphic morphology, whereas a derived shape characterizes extant Aegothelidae, Apodini and Trochilidae. Furthermore, we describe the first partial skeleton of the earliest aegialornithid species, Primapus lacki Harrison & Walker, 1975, which was previously only known from the humeri of the type series that stem from different sites of the London Clay. The apodiform birds from Walton-on-the-Naze show a considerable taxonomic and ecomorphological diversity, and whereas Eocypselus may have inhabited forest edges and caught insects by sallying flights from perches, Primapus probably was a fast-flying and more aerial bird.

Given the frequency with which translocation is implemented as a conservation tool, remarkably little research has assessed the sustainable management of translocation source populations. We sought to make an a priori estimate of the impact of multiple alternative harvesting scenarios on five passerine species endemic to Norfolk Island which may benefit from future translocation. Population parameters for our five focal taxa were quantified using distance sampling at 298 point surveys conducted in 2019. Intensive nest monitoring between 2018 and 2020 was used to estimate reproductive rates. We modelled population trajectories for all five taxa under alternative harvesting scenarios in forward projections over a 25-year period to assess the likelihood that focal populations could recover from a harvesting event. We used sensitivity analysis to assess the robustness of models to uncertainty around some population parameters. We estimate that Norfolk Island National Park supported 1486 Norfolk Robins Petroica multicolor (95% confidence interval (CI) 1017–1954), 7184 Slender-billed White-eyes Zosterops tenuirostris (95% CI 5817–8551), 2970 Norfolk Grey Fantails Rhipidura albiscapa pelzini (95% CI 2094–3846), 3676 Norfolk Gerygones Gerygone modesta (95% CI 2869–4482) and 1671 Norfolk Golden Whistlers Pachycephala pectoralis xanthoprocta (95% CI 1084–2259) in 2019. All five species were predicted to recover from the harvest of 50, 100 or 150 individuals within 10 years. Despite considerable variation in population parameters, we demonstrate that all five focal taxa have the potential to sustain harvesting at rates required for future conservation translocations. We provide a clear comparison of differing intensity harvesting strategies for on-ground managers. More broadly, we provide a rare example of an a priori assessment of the impact of harvesting for translocation.