La estacionalidad afecta a la distribución de especies de aves, pero no a los patrones de diversidad y anidamiento en los parques urbanos de Vitoria–Gasteiz (España)

Environmental seasonality leads to variation in the composition and structure of bird communities over the year that might alter biodiversity and nestedness patterns in urban parks and other frag-mented habitats. These changes could have important implications in the management and conservation of urban green areas and their populations, but they are largely unexplored. In this study, the composition, diversity and nestedness of the breeding and wintering avian communities in 31 urban parks of Vitoria–Gasteiz (Spain) were analysed. Avian diversity was significantly greater during breeding than during the winter period, although the most diverse parks during breeding were also the most diverse during winter. Most of the among–park variation in diversity was explained by park size, while tree density had a marginal contribution that was only significant during winter. Avian communities showed a significant nested subset pattern that was similar between seasons, with these patterns being mainly mediated by park size. Although the distribution of seven out of the 16 species occurring all–year–round changed significantly from one season to the other, the park ranks in the nestedness matrices were strongly correlated between seasons. This was caused by the reduction in the park distribution of some species from one season to the other that was compensated by the expansion of other species that were initially less common. These results support the idea that, in small and medium–sized cities, park size is the main constraint on avian diversity, and the presence of relatively large parks (> 10 ha) should be encouraged to promote a rich avifauna all year round.La estacionalidad afecta a la distribución de especies de aves, pero no a los patrones de diversidad y anidamiento en los parques urbanos de Vitoria–Gasteiz (España). La estacionalidad ambiental causa variaciones en la composición y estructura de las comunidades de aves a lo largo del año que podrían alterar los patrones de biodiversidad y anidamiento en los parques urbanos y otros hábitats fragmentados. Estos cambios podrían tener importantes implicaciones en la gestión y conservación de las áreas verdes urbanas y sus poblaciones de aves, que se han estudiado poco. En este estudio se analizaron la composición, la diversidad y el anidamiento de las comunidades de aves reproductoras e invernantes en 31 parques urbanos de Vitoria–Gasteiz (España).La diversidad de aves fue significativamente mayor durante la época reproductiva que en el período invernal, aunque los parques más diversos durante la reproducción también fueron los más diversos en invierno. La mayor parte de la variación de la diversidad entre parques se explicó por el tamaño del parque, mientras que la densidad del arbolado tuvo una contribución escasa que solo fue significativa en invierno. Las comunidades de aves mostraron un patrón de anidamiento significativo y similar en ambas estaciones, que estaba fundamentalmente determinado por el tamaño del parque. A pesar de que la distribución de siete de las 16 especies que están presentes todo el año cambió significativamente de una estación a otra, las posiciones de los parques en las matrices de anidamiento estuvieron estrechamente correlacionadas entre estaciones. Ello es debido a que la reducción de algunas especies en los parques de una estación a otra se vio compensada por el aumento de otras especies que inicialmente eran menos comunes. Estos resultados apoyan las ideas de que, en ciudades de pequeño y mediano tamaño, la superficie del parque es el principal factor limitante de la diversidad de aves, y que debería fomentarse la existencia de parques relativamente grandes (> 10 ha) para favorecer una rica avifauna durante todo el año

Early arrival is not associated with more extra-pair fertilizations in a long-distance migratory bird

When assessing the benefits of early arrival date of migratory birds, a hidden and often ignored component of males’ fitness is the higher chance of early-arriving birds to obtain extra-pair fertilizations. Here we investigated how extra-pair paternity might affect the relationship between male arrival date and number of fertilizations in a model study system, the European pied flycatcher Ficedula hypoleuca. For this purpose, we sampled and genotyped breeding pairs, unpaired males and offspring (including embryos from unhatched eggs when possible) of a Dutch pied flycatcher population. Detailed information on arrival date of males, egg laying date of their social mates and nest success was also recorded. Earlyarriving males had early-laying females and males with early-laying females had a higher probability of siring extra-pair eggs and obtain more fertilizations. However, male arrival date alone did not correlate with the probability to gain extra-pair paternity and neither to the amount of fertilized eggs. Both early- and late-arriving males had a higher probability of losing paternity in their own nest compared to birds with an intermediate arrival date. Finally, late-arriving males were more likely to remain unpaired but, interestingly, a few of these birds obtained paternity via extra-pair copulations. Because earlier arrival date did not lead to more extra-pair fertilizations and because such relationship seems to be driven mainly by the female’s laying date, we conclude that the contribution of extra-pair paternity to the overall fitness benefits of early male arrival date is relatively small

Feather growth rate and mass in nearctic passerines with variablemigratory behavior and molt pattern

Bird species vary greatly in the duration of their annual complete feather molt. However, such variation is not well documented in birds from many biogeographic areas, which restricts our understanding of the diversification of molt strategies. Recent research has revealed that molt duration can be estimated in passerines from ptilochronology-based measurements of the growth rate of their tail feathers. We used this approach to explore how molt duration varied in 98 Nearctic species that have different migratory strategies and molt patterns. As previously documented for Palearctic species, migration was associated with a shortening of molt duration among species that molted during summer on their breeding range. However, molts of winter-molting migratory species were as long as those of summer-molting sedentary species, which suggests that winter molt also allows Nearctic migrants to avoid the temporal constraints experienced during summer. Our results also suggest that migratory species that undergo a stopover molt within the Mexican monsoon region have the shortest molt duration among all Nearctic passerines. Interestingly, and contrary to expectations from a potential tradeoff between molt duration and feather quality, observed variation in feather growth rate was positively correlated with differences in tail feather mass, which may be caused by differences among groups in the availability of resources for molting. We encourage the use of similar approaches to study the variation in molt duration in other geographic areas where knowledge of the evolution of molt is limited.

Conservación de poblaciones singulares ante el cambio climático: el caso de las currucas capirotadas ibéricas

Depto. de Biodiversidad, Ecología y EvoluciónFac. de Ciencias BiológicasTRUEpu

Stopover ecology of autumn-migrating Bluethroats (Luscinia svecica) in a highly anthropogenic river basin

Wetlands are highly productive habitats used by many avian species as stopover sites during their migrations. However, these habitats are highly threatened by anthropogenic activities, such as land-use changes, the introduction of exotic species, and global warming. Further understanding on the spatiotemporal use of wetlands and their surrounding areas by migrating birds is essential to predict how these changes might affect avian en route ecology. We selected a habitat-generalist passerine, the Bluethroat Luscinia svecica, as model of how migratory birds exploit a highly anthropogenic river basin in southwestern France (i.e. Barthes de la Nive) during autumn migration. We captured and radiotracked 29 young Bluethroats in this region to shed light on different aspects of their stopover ecology and behavior such as stopover duration, habitat selection, and home-range size. We also characterized Bluethroat diet and arthropod availability in different habitats. Bluethroats positively selected pure or mixed reed beds (associated with sedge), hydrophilous tall grasslands, and corn crops. Birds staying more than one day, 8.4 days on average, used preferably corn crops. Home-range sizes were on average 5.8 ha (fixed kernels K95) and high-occupancy area (K50) was 1.36 ha with large individual variation. Bluethroats stopping over with low fuel loads tended to have larger home ranges and used preferentially corn crops, wet, or mesotrophic grasslands and rural paths. Reed beds were typically used as roosting habitat for the majority of birds, being on average 397 m apart from their daytime core areas. Short-staying birds tended to show higher fuel loads and restricted their activities to a smaller home range (1 ha) in pure and mixed reed beds. The diet of Bluethroats was dominated by ants, spiders, and beetles that were particularly abundant in corn crops. The use of corn crops by autumn-migrating Bluethroats in our study site seems to be a reasonable solution in a highly altered environment. Reducing the use of insecticides in these crops and delaying the harvesting time after mid-October are two supplemental measures that, together with a good management of the remaining wetland patches, could greatly favor Bluethroats and other migratory species in this region

Atracción de otras especies por reproducciones del canto del Pechiazul Luscinia svecica durante la migración otoñal: un test experimental empleando datos de anillamiento

Song playback of a particular avian species is well-known to have the potential to bias the sample of conspecifics that can be captured during mist-netting sessions, with respect to sex, age or body condition. However, the possibility that playback affects heterospecific captures has been less explored and lacks solid experimental evidence. In this study, we used an experimental approach to test whether Bluethroat Luscinia svecica song playback altered the overall number of individuals of other species captured during autumn migration in a wetland in southwestern France. We found that playback increased the capture rates of species that were not the direct target of the playback. This heterospecific attraction effect should be assessed and carefully considered when designing any avian monitoring programme.El uso de reproducciones sonoras de una especie de ave concreta es bien conocido que tiene el potencial de sesgar la muestra de conespecíficos (con relación al sexo, edad o condición corporal) que pueden ser capturados durante las sesiones de anillamiento con redes japonesas. Sin embargo, la posibilidad de que los reclamos sonoros afecten a las capturas de heterospecíficos ha sido menos explorada y carece de evidencias experimentales sólidas. En este estudio testamos experimentalmente si el uso de reclamos de pechiazul Luscinia svecica alteraba el número total de heterospecíficos capturados durante la migración otoñal en una zona húmeda localizada en el suroeste de Francia. Nuestros resultados muestran que el uso de reproductores sonoros incrementa las tasas de capturas de especies que no fueron el objetivo directo del reproductor. Este efecto de atracción por heterospecíficos debería ser evaluado y considerado cuidadosamente a la hora de diseñar cualquier programa de seguimiento de aves

Habitat distribution of migratory and sedentary blackcaps Sylvia atricapilla wintering in southern Iberia: a morphological and biogeochemical approach

In migratory species, the way in which conspecifics from different breeding populations 3 are distributed during the non-breeding period is important from and ecological, 4 evolutionary and conservation perspective, but such knowledge is still limited for most 5 species. Migratory and sedentary blackcaps Sylvia atricapilla wintering in southern Spain 6 can occupy two habitat types: forests and shrublands. According to earlier studies, 7 blackcaps prefer forests over shrublands, and residents remain nearly restricted to forests. 8 However, whether migrants with different breeding origin occupy the two habitats 9 differently is unknown. We used morphological and biogeochemical data (hydrogen isotope ratios measured on feathers: δ2 10 Hf), which show variation along the breeding range 11 of the species, to answer this question. Isotope analyses supported the reliability of 12 morphology as a method for distinguishing between migratory and sedentary blackcaps in 13 sympatry, showing that sedentary individuals are rare in shrublands while migratory ones are abundant in both habitat types. However, migratory blackcaps scored similar δ2 14 Hf 15 values in forests and shrublands, and neither did vary in structural size or flight 16 morphology between habitats. Our study suggests that migrants from a wide range of 17 breeding origins end up mixing between forests and shrublands, which may explain the 18 patterns of variation in space and time in the abundance of blackcaps in this area, and 19 supports the view that inequalities may arise among migrants with the same origin but 20 wintering in different habitats. Such inequalities might carry over into other stages of 21 blackcaps’ life cycle contributing to the regulation of its migratory population

Timing manipulations reveal the lack of a causal link across timing of annual-cycle stages in a long-distance migrant

Organisms need to time their annual-cycle stages, like breeding and migration, to occur at the right time of the year. Climate change has shifted the timing of annual-cycle stages at different rates, thereby tightening or lifting time constraints of these annual-cycle stages, a rarely studied consequence of climate change. The degree to which these constraints are affected by climate change depends on whether consecutive stages are causally linked (scenario I) or whether the timing of each stage is independent of other stages (scenario II). Under scenario I, a change in timing in one stage has knock-on timing effects on subsequent stages, whereas under scenario II, a shift in the timing of one stage affects the degree of overlap with previous and subsequent stages. To test this, we combined field manipulations, captivity measurements and geolocation data. We advanced and delayed hatching dates in pied flycatchers (Ficedula hypoleuca) and measured how the timing of subsequent stages (male moult and migration) were affected. There was no causal effect of manipulated hatching dates on the onset of moult and departure to Africa. Thus, advancing hatching dates reduced the male moult–breeding overlap with no effect on the moult–migration interval. Interestingly, the wintering location of delayed males was more westwards, suggesting that delaying the termination of breeding carries over to winter location. Because we found no causal linkage of the timing of annual-cycle stages, climate change could shift these stages at different rates, with the risk that the time available for some becomes so short that this will have major fitness consequences

Feather traits in four southern populations of the Eurasian blackcap Sylvia atricapilla: do altitudinal movements explain the differences?

Moult of birds is shaped by environmental and genetic drivers whose relative contribution to the structure of feathers may differ within and between populations. In this study, we compare some traits of tail feathers (growth bars, mass, rachis width and barb length) between four populations of the Eurasian blackcap Sylvia atricapilla breeding at different elevations within the southwestern Palaearctic. We tested if these traits were related to the primary productivity of habitats (a surrogate of food availability) or were better explained as an adaptation to altitudinal movements. The distribution of primary productivity was positively related to blackcap abundance suggesting that the species tracked the most productive areas to breed. In this environmental setting, wing morphology (wing length, concavity and pointedness) suggested that lowland blackcaps were sedentary while blackcaps from highland areas were involved in altitudinal movements. The feathers of blackcaps inhabiting the highlands showed wider growth bars and rachis than those of the most productive lowland areas but did not differ in feather mass and barb length. Fast feather growth has been related to time constraints to moult and wider rachis to improve flight efficiency in migratory birds. Our results therefore suggest that differences in feather characteristics between southern populations of the Eurasian blackcap are better interpreted as an adaptive response to altitudinal migration than as a consequence of regional food availability