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Understanding habitat selection patterns in congeneric species has raised special interest due to its importance when designing conservation strategies for the species. We analysed reproductive habitat selection of three coexisting warbler species in the eastern Iberian Peninsula. We detected the individuals by their vocalizations at 40 listening points in two study areas (Carcaixent and Alcoy). We used satellite images to identify different vegetation types and their availability. Reproductive habitat selection was analysed by the Ivlev selectivity index and a compositional analysis. In addition, we determined the effect of different habitat variables (dominant vegetation, vegetation height, cover and site) on the presence of the species fitting a binomial GLM with logistic linking function. We found that the Sardinian Warbler (Curruca Melanocephala) selected scrub-dominated areas; while the Dartford Warbler (C. undata) preferred areas with low (<50%) vegetation cover; and the Subalpine Warbler (C. cantillans) was present in areas with scrubs and low (<50%) vegetation cover, avoiding crops. The compositional analysis showed that the species used different vegetation types, in relation to their availability and that the selection differed between species. The Sardinian Warbler was the only species which showed spatial variation in reproductive habitat selection. Our results evidence that the studied warbler species select and avoid different types of vegetation in relation to their specific requirements and the present habitat structure. This represents valuable information to understand the composition of local communities and the reproductive habitat selection of the studied species. [ABSTRACT FROM AUTHOR]

This study aimed to monitor the demographic changes of some closely related species based on bird ringing data from the CES (Constant Effort Sites) program in Hungary between 2007 and 2018, and to explore the reasons for these demographic changes. The CES program tracks breeding bird populations with standard methods. The studied species breeding in Hungary were from genera Sylvia, Curruca, and Phylloscopus. Among these species, the trends of some forest birds, like Eurasian Blackcap (Sylvia atricapilla), Lesser Whitethroat (Curruca curruca), Common Chiffchaff (Phylloscopus collybita) and Willow Warbler (Ph. trochilus) showed no substantial changes, and one of the open-habitat species, the Barred Warbler (Curruca nisoria) – a long distant migrant – showed decreasing trends. The Garden Warbler (Sylvia borin) – a trans-Saharan migrant but forest dweller – also experienced population declines. Short-distance migrants maintained stable populations. Common Whitethroat productivity displayed an increasing trend to compensate for population decline. Upon examining the Eurasian Blackcap, this study detected a strong relationship between the number of adult birds, productivity, and the number of adults captured the following year. [ABSTRACT FROM AUTHOR]

In migratory birds, constraints due to breeding are relaxed during the non-breeding season and thus, social behaviours and spatial associations are potentially more directly coupled to food resources and habitats. Use of space and territorial behaviour has rarely been studied in Afro-Palearctic migrants. Variation in strategies could exist among species within the same habitat because of differences in foraging, diet and microhabitat. We compare use of space and association with conspecifics in Common Chiffchaffs Phylloscopus collybita and Subalpine Warblers Sylvia cantillans at a non-breeding site in northern Senegal using radio telemetry and playback experiments. Home ranges of Chiffchaffs were larger and overlapped more than those of Subalpine Warblers. Though Chiffchaffs were often close together, we found no signs of spatial association among individuals in either species. Chiffchaffs showed no clear pattern of territorial response to conspecific song; whereas, playback elicited a territorial response in most Subalpine Warblers. Our results suggest species-specific differences in use of space that might reflect differences in foraging ecology and microhabitat. [ABSTRACT FROM AUTHOR]

The evolution of migration in birds and its causes are still subject of debate. Recent studies tracking current bird migration have identified peaks in net primary productivity (NPP) as a main driver of bird migratory behaviour. However, it is unclear which variables may have played a major role in the evolution of bird migration at deeper phylogenetic levels. Here, we used phylogenetic comparative methods to assess whether the evolutionary patterns of migratory distances, as a proxy for migratory behaviour, are correlated with several biometric, climatic and productivity variables in a phylogenetic context, using Sylvia warblers as a case study. Our results recover NPP in the breeding range and during the breeding season as the variable with stronger positive correlation with migratory distances, being always included in the best models considering all potential variables. Several climatic variables show a correlation with the evolution of migration, but those are also tightly correlated with NPP. Among morphological variables, migratory lineages tend to have longer wings than sedentary ones. Although NPP has been identified as a driver of migratory behaviour in current species, in a phylogenetic scale it is not possible to disentangle if it was a main driver in the evolution of bird migratory behaviour or a consequence of it, yet migration and NPP seem to be tightly related today and along the long evolutionary history of these passerines. The evolution of migration in birds and its causes are still subject to debate. It is unclear which variables may have played a major role in the evolution of bird migration at deeper phylogenetic levels. Here, we used phylogenetic comparative methods to assess whether the evolutionary patterns of migratory distances, as a proxy for migratory behaviour, are correlated with several biometric, climatic and productivity variables in a phylogenetic context, using Sylvia warblers as a case study. Our results recover Net Primary Productivity (NPP) in the breeding range and during the breeding season as the variable with stronger positive correlation with migratory distances. Migration and NPP seem to be tightly related today and along the long evolutionary history of these passerines. [ABSTRACT FROM AUTHOR]

Aim The ecological niche of a species is dynamic at a variety of spatial and temporal scales; embracing this complexity is required for accurate assessment of species' niche requirements and to forecast how species will respond to novel and dynamic climates. In the context of recent advances in species distribution modelling, however, both the environment and the ecological niche of a species have often been treated and quantified as static entities. Here, our aim was to explore how species' realized niches and geographical ranges are dynamically shaped by the decoupled spatio-temporal availability of different environmental conditions, using the migration of Sylvia warblers as an example. Location Palaearctic, Afrotropical and Indo-Malay ecozones. Methods We used a species distribution modelling approach to evaluate the niche characteristics of Sylvia warblers under their actual migration strategies as well as null models assuming resident behaviour. We focused on climate and land cover as niche dimensions, taking into account the spatial availability of environmental conditions during the peak breeding and non-breeding season for each Sylvia species. Results Migration did not increase the overlap between breeding and non-breeding niches compared with breeding and non-breeding niche overlap in resident null models. Sylvia warblers did not compensate for the costs of a longer migratory journey by tracking their climatic niche or land-cover niche more closely. Instead, Sylvia warblers migrated further than the closest available area with suitable climate and land cover. Main conclusions Climatic niche tracking is unlikely to be the main driver of migration in Sylvia warblers. We suggest that taking dynamic environments into account and comparing actual niche characteristics to those resulting from alternative possible range dynamics enhances our understanding of the drivers behind organisms' movements and distributions. [ABSTRACT FROM AUTHOR]

Aim As global temperatures have increased, many species distributions have exhibited polewards shifts, a trend that is predicted to continue in future decades. However, the mechanisms underlying such shifts are not well understood. Here we quantify the impact of large-scale variation in temperature on reproductive output within a group of migratory birds to assess the potential for future range changes. Location Western Europe. Methods We use data from captures of 350,000 individual birds, collected under constant effort ringing protocols from 1994-2006, to estimate productivity (percentage of juveniles caught) for seven species of migrant warblers (family Sylviidae) breeding in Europe in relation to spring temperature and latitude by fitting generalized linear mixed models. Results Productivity was highest at mid-latitudes for six of our seven study species and did not change significantly over the study period. Only one species (reed warbler, Acrocephalus scirpaceus) showed increased productivity at northern sites as expected. Six of the seven species also showed evidence for local adaptation, with productivity decreasing as temperatures diverged from the local mean. However, for three of these species the 'optimum' temperature was greater than the local mean temperature at the majority of sites. Main conclusions These results indicate that latitudinal gradients in productivity are likely to influence large-scale abundance patterns, but that adaptation to local climate conditions has the potential to constrain the rate of northward range shifts in many species. [ABSTRACT FROM AUTHOR]