Journal of Ornithology

Dispersal constitutes one of the main processes that shape population genetic structure and dynamics. Combining a capture-mark-resighting methodology and molecular genetics analyses, we studied the natal dispersal behaviour of House Wrens (Troglodytes aedon bonariae) inhabiting a naturally fragmented habitat in south temperate Argentina. Based on data collected over 12 breeding seasons (2005–2016), we tested if males and females differ in natal dispersal behaviour at different spatial scales. At local scale (within study sites), both resighting of banded individuals and genetic analysis showed that females dispersed greater distances than males. At a broader spatial scale (between study sites) resighting of banded individuals could not verify that females were the dispersing sex since long-distance dispersal was rare. However, genetic analyses revealed paradoxical evidence: while the females of populations separated by more than 5 km showed slight but significant genotypic differences among them, males showed genetic differences at a greater distance (> 16 km). Given that genetic analyses can provide evidence of both historical and present-day dispersal the observed genetic differentiation does not necessarily imply that the sex dispersal pattern is reversed at a regional scale. We propose that females have a higher probability of acquiring a partner/territory at closer distances due existing male-biased population sex ratio caused but higher female mortality. Also, although males are less likely to disperse, when they do, they must travel greater distances to find a suitable territory or mate. Such movements would prevent the occurrence of genetic differences among male populations.

Seventy-three of the 280 species of Galliformes are at risk of extinction, and all of them are threatened by human factors (mainly hunting and deforestation). Reintroduction is increasingly proposed as a conservation measure, although there is limited post-release monitoring to determine success. The science of reintroduction biology is still in its infancy in Brazil, mainly because most of the projects involving release of animals seldom include post-release monitoring, data collected are not published, and release areas are frequently chosen without any criteria. The Red-billed Curassow Crax blumenbachii reintroduction program in Brazil can be considered a good model for developing future Brazilian reintroduction projects. Systematic radio-tracking of released Red-billed Curassows has allowed detailed information on the ecology and behavior of the species. The information obtained through post-release monitoring will guide future management of the species, and it is a good example of the use of reintroduction as a conservation tool for threatened Galliformes.

Reproduction of Tickell’s Leaf Warblers Phylloscopus affinis was studied in an alpine valley (29°27′N, 91°40′E, 3,980–5,600 m) in the Lhasa mountains, Tibet, at the upper elevational limit of the species’ breeding range. This species is a summer breeder, and is the only breeding Phylloscopus species in the valley. It nested in all types of shrubby vegetation across the altitudinal range of the valley. Most nests were placed close to the ground (<1 m) in low thorn bushes. Egg-laying dates fell between late May and early July, most within the first 3 weeks after the commencement of breeding. Mean clutch size was 4.0 (3–5) and mean brood size at fledging 3.4 (2–5). Incubation was by the females and lasted 13–14 days, and both parents cared for the young for 14–17 days. Nestlings ready to leave the nest were 13% heavier than the adults. Overall, 76% of nesting attempts produced at least one fledged young. Some aspects of the breeding biology of this high-altitude warbler were compared with those of lower-altitude Phylloscopus species.

Recent studies show that traits long recognized as sexually selected ornaments, such as the bright plumage colors and melodious vocal displays of songbirds, have evolved in surprising ways. Male plumage colors are generally more elaborate and diverse than female colors, and in many species only males sing, so both of these dimorphisms are widely presumed to have evolved through sexual selection on males. Yet, in multiple widely divergent songbird clades, sexual differences in colors and songs have evolved through losses in females rather than gains in males. Indeed, changes in female phenotypes may be the principle driving factor affecting such sexual dimorphisms in most songbirds. Sexual dichromatism and song dimorphism also tend to be associated with life history traits other than mating system, such as seasonal migration or territorial behaviors. Altogether, these recent findings support the view that sexual dimorphism is an evolutionary byproduct of multiple, different selection pressures acting on each sex rather than just sexual selection on males. Researchers should therefore be cautious to avoid assuming that dimorphism itself is a character solely reflecting levels of sexual selection in species.

Males in many bird species develop elaborate carotenoid-based plumage ornaments which often play an important role as signals of individual quality in intra- or intersexual selection. However, knowledge of the pattern of age-related variation in plumage traits is crucial to interpret results on associations between plumage signals and reproductive performance. We investigated how age is related to brightness and carotenoid saturation of the orange-red breeding plumage in males of known age in the Red Bishop (Euplectes orix), a polygynous and sexually dimorphic weaverbird species. We found that the relationships of both plumage brightness and carotenoid saturation with age were best explained by a quadratic function, with males in their prime (i.e. 3–5 years old) having a brighter and more carotenoid-saturated plumage than both very young and very old males. The implications of our results for studies in the context of animal signalling are discussed.

Field margin management is a common measure employed in Europe to support farmland bird populations. In this study we found and analysed 237 nests of the Skylark Alauda arvensis in the Netherlands over a period of 6 years to determine the effects of arable field margins and breeding crop on nest-level reproductive success. Additionally, the effect of field margins on predation was investigated and food availability in crops and field margins was compared. Neither clutch size, nest survival nor nestling body weight were improved by field margin availability, irrespective of the breeding crop used. However, the choice of breeding crop had important effects. Nestling weight was significantly lower in cereals than in grassland and lucerne, corresponding with the low prey densities present in cereals. Nest survival was lowest in grassland due to frequent silage cutting. Predation rates were highest in cereals but were not affected by field margin proximity. The highest reproductive success was achieved in lucerne, which was mown twice a year and retained a suitable height for breeding throughout the breeding season. We conclude that field margins are not sufficient to maintain a Skylark population in this intensively farmed area. The presumably more subtle effects of increased food availability cannot compensate for the high nest failure rates resulting from agricultural operations and predation. In this and similar areas, the provisioning of safe nesting habitat throughout the breeding season is essential to improve breeding performance. Our research suggests that this can be achieved by reducing the frequency of silage cutting on grassland and by increasing the surface area of lucerne.