Search

Above all, bird ringing must be safe for birds, for ethical reasons but also to ensure that data collection is not biased by marking effects. Bird ringing schemes are responsible for determining the size of the rings used to mark birds individually. This paper critically reviews the recommended ring sizes in the Aranzadi Ringing Scheme and proposes an objective criterion for ringers. A morphological analysis of tarsus width (MTW) and the width of the tibia–tarsus articulation (MAW), over a sample of more than 4000 individuals of 74 species of both passerines and non-passerines captured in Spain, revealed that the mean difference between the internal diameter of the recommended ring (IDR) and MTW was 32% in relation to MTW (sd 15.8%, 95% confidence interval 28–35%). Experience demonstrates that this clearance is adequate, but recommendations for rings with clearances either too narrow (<6%) or too wide (>50–60%) should be reviewed and changed, if possible, to bring them closer to a 32% standard. [ABSTRACT FROM AUTHOR]

River systems are some of the habitats most drastically affected by climate change. Consequently, many riparian species are amongst the most threatened living organisms worldwide, making riparian areas a conservation priority. Demographic analyses destined to improve our comprehension of the population dynamics of riparian species are crucial in this context. The present work analyses the spatio-temporal demographic dynamics of a presumably well-preserved White-throated Dipper (Cinclus cinclus) population from northern Spain. Using multistate models where we considered the effects of factors such as mean water flow in winter, age, sex, hydrographical basin of origin and hatching date, we found that the population had a constant annual dispersal rate (ψ = 0.038; 95% CI: 0.022-0.065). The mean apparent survival of Dippers from first-order clutches was 0.18 (95% CI: 0.12-0.22), whereas for those hatched in second-order clutches was 0.07 (95% CI: 0.03-0.15). The mean annual apparent survival for adults was 0.64 (95% CI: 0.56-0.70). Although apparent survival varied from year to year, we found no effect of the average winter flow on this parameter. Recapture probability (p) varied among basins, probably reflecting a heterogeneous sampling effort. In conclusion, using multistate models were found that Dippers from three adjacent river basins in northern Spain had a very short-range natal dispersal rate, and a breeding dispersal close to zero, a trait that could be different from findings in other zones of Spain, where dispersal rates seem to be much higher. [ABSTRACT FROM AUTHOR]

Copyright of Ibis is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During migration, landbirds normally need to stop-over in order to rest and/or acquire fuel stores that power their flight. Refuelling strategies become particularly evolutionarily relevant when birds must cross broad geographic barriers, where the chance to land and get food is nil, such as when crossing oceans. Our objective was to learn more about the use of the small islands located close to the mainland coast as stopover areas by small migratory birds that cross the Bay of Biscay. Using data collected in a constant-effort mist-netting programme conducted on Izaro Island (northern Spain) during autumn migration (years 2018 to 2021), we aimed to determine (1) which species land on the island and for how long they stay there, and (2) their fuel load and fuel deposition rate. Structurally, the assemblage was dominated by Willow Warblers Phylloscopus trochilus, which on average accounted for 84% of the abundance. Clustering analyses reveal that the assemblage was rather homogeneous across the four study years. Most birds probably stayed on the island for less than 24 hours, with fewer than 5% being recaptured one or more days after their first capture. The first-capture-event body mass of Willow Warblers captured only once (8.0g, 95%CI 7.8-8.4g) did not differ from the initial body mass of those captured two or more times within a season (8.0g, 95% CI 7.0-9.0g), and those stopping over on Izaro had a negative mean fuel deposition rate of –0.2g/day (SE = 0.1g/d). Overall, Izaro was used as an emergency stopover site during the course of this study, where exhausted birds landed after sea-crossings. From a conservation standpoint, and as compared to other stopover sites used as 'emergency' stopover sites, results suggest that Izaro is of little value for replenishing the fuel stores of these small birds during autumn migration.—Betanzos-Lejarraga, L., Guzmán, I., Escandell, R., Unamuno, E. & Arizaga, J. (2023). Stopover ecology of passerine birds on an islet in the Bay of Biscay in autumn reveals a pattern similar to their use of small Mediterranean islands in spring. Ardeola, 70: 241-255. Durante la migración, las aves terrestres normalmente necesitan detenerse para descansar o adquirir las reservas que después consumirán durante el vuelo. Las estrategias para ganar estas reservas se vuelven particularmente relevantes desde el punto de vista evolutivo cuando las aves han de cruzar grandes barreras geográficas en las que la posibilidad de aterrizar y alimentarse es nula, como ocurre al atravesar océanos. El objetivo de este artículo es profundizar en el uso de las pequeñas islas situadas cerca de la costa por las pequeñas aves migratorias que cruzan el golfo de Vizcaya. Utilizando los datos que fueron recolectados mediante un programa de anillamiento científico desarrollado en la isla de Izaro (norte de España) durante el periodo de paso posnupcial (años 2018 a 2021), se pretendió identificar (1) cuáles son las especies que usan la isla y cuánto tiempo permanecen allí, y (2) cuál es su cantidad y tasa de deposición de reservas. Estructuralmente, el ensamblado estuvo dominado por el mosquitero musical Phylloscopus trochilus, que en promedio representó el 84% de la abundancia. Los análisis de clusters revelaron un ensamblado muy homogéneo a lo largo de todo el periodo de estudio. En general el periodo de estancia en la isla fue de un día para la mayoría de los ejemplares capturados para anillamiento, y de ellos menos del 5% fueron recapturados uno o más días después de su primera captura. La masa corporal de la primera captura no varió entre mosquiteros musicales capturados una sola vez en la isla (8,0 g, IC 95 % 7,8-8,4 g) y capturados dos o más veces en la temporada (8,0 g, IC 95 % 7,0-9,0 g). La tasa de ganancia de reservas de los recapturados fue negativa (–0,2 g/d; SE = 0,1 g/d). En general, nuestros resultados sugieren que Izaro es usada como punto de parada migratoria de emergencia por las aves que, tras cruzar el Cantábrico, llegan exhaustas a la costa del norte de España. Desde el punto de vista de la conservación, y en comparación con otros sitios de parada migratoria utilizados, Izaro parece tener poco valor como punto de ganancia de reservas durante el periodo de paso posnupcial. —Betanzos-Lejarraga, L., Guzmán, I., Escandell, R., Unamuno, E. y Arizaga, J. (2023). La ecología de parada de descanso migratorio de las aves paseriformes en un islote del golfo de Vizcaya en otoño revela un patrón similar al uso de las pequeñas islas mediterráneas en primavera. Ardeola, 70: 241-255. [ABSTRACT FROM AUTHOR]

Simple Summary: Urban areas are constantly increasing, as well as human activities related to them. This can lead to an effect in bird populations due to the alterations caused in nature. According to the latest national censuses in Spain, House Sparrow and Eurasian Tree Sparrow populations are decreasing. In this study, we used ringing station data from Spain to assess the tendency of both populations over a two-decade period of time. We also tried to determine the relation of these two populations and their breeding success with the habitat composition. The data analysis confirmed the decreasing trend in both species. However, Eurasian Tree Sparrow showed signs of increasing presence in urban areas, contrary to our predictions. Furthermore, the productivity of both populations remained stable over the study years. Urban areas are constantly increasing, which can cause an effect in bird populations since human activities lead to nature alterations. Populations of House Sparrow (Passer domesticus) and Eurasian Tree Sparrow (Passer montanus) have been decreasing in Spain according to the latest national censuses in Spain. In this study, we tried to assess the population trend over more than two decades using ringing data from Spanish constant effort sites, as well as to determine the population and breeding success proxy in relation to habitat composition at landscape level. We analysed the data and confirmed the decreasing trend in the two species. However, Eurasian Tree Sparrow showed signs of increasing presence in urban areas. Furthermore, the productivity remained stable over sampling sites and years, meaning that the causes of the decreasing populations are affecting both adult and juvenile individuals. [ABSTRACT FROM AUTHOR]

Carotenoid-based ornaments are often considered reliable (honest) individual condition signals because their expression implies physiological costs unaffordable for low-quality animals (handicap signals). Recently, it has been suggested that efficient cell respiration is mandatory for producing red ketocarotenoids from dietary yellow carotenoids. This implies that red colorations should be entirely unfalsifiable and independent of expression costs (index signals). In a precedent study, male common crossbills, Loxia curvirostra, showing a red plumage reported higher apparent survival than those showing yellowish-orange colors. The plumage redness in this species is due to ketocarotenoid accumulation in feathers. Here, we correlated the male plumage redness (a 4-level visual score: yellow, patchy, orange, and red) and the body morphology in more than 1,000 adult crossbills captured in 3 Iberian localities to infer the mechanisms responsible for color evolution. A principal component analysis summarized morphometry of 10 variables (beak, wing, tarsus length, etc.). The overall body size (PC1) and the length of flight feathers regarding body size (PC3) showed significant positive relationships with plumage redness. Plumage redness was barely correlated with bill shape measures, suggesting no constraint in acquiring carotenoids from pine cones. However, large body sizes or proportionally long flying feathers could help carotenoid acquisition via social competition or increased foraging ranges. Proportionally longer flight feathers might also be associated with a specific cell respiration profile that would simultaneously favor flying capacities and enzymatic transformations needed for ketocarotenoid synthesis. Such a phenotypic profile would agree with the hypothesis of ketocarotenoid-based colors acting as individual quality index signals. [ABSTRACT FROM AUTHOR]

Aim: In temperate mountain ranges, sharp spatial variations in habitat heterogeneity and climate provide a perfect study setup to assess genetic and phenotypic differentiation in bird populations. In this paper, we analysed morphological divergence patterns across geographical and environmental gradients, in correlation with genetic differentiation and geographical isolation, in the breeding grounds of a long‐distance migratory passerine. Location: Northwestern Iberian mountains. Taxon: The Iberian bluethroat, Luscina svecica azuricollis. Methods: We collected a sample of 625 Iberian bluethroats across their whole breeding range to measure body weight and tarsus length, as well as wing length and pointedness. Morphological differentiation across geographical (latitude and elevation) and environmental (climate and vegetation) gradients was assessed using generalized linear mixed models. Additionally, the role of genetic distance and geographical isolation as drivers of morphological differentiation was evaluated with Mantel tests. Results: Bird morphology varied significantly with latitude and elevation, but not with climate or vegetation. In the case of latitude, morphological differences in body size were contrary to Bergmann's rule statements. All biometric and morphometric variables diverged among localities. A similar trend was found for genetic clusters, except for wing shape. Body weight and wing length were both correlated with geographic distance, while only the former varied with genetic differentiation. The greatest genetic and phenotypic differentiation was detected in the southernmost mountain range, that holds the most geographically isolated genetic group. Main conclusion: Evidence suggests that the strong morphological differentiation observed in the Iberian breeding bluethroat across geographical gradients results from the combination of unambiguous deterministic forces, such as ecological selection mechanisms, and other factors, such as geographical isolation, that can be either deterministic, stochastic or both, all acting at different scales. [ABSTRACT FROM AUTHOR]

We aimed to describe the morphologic and isotopic differences of European Goldfinches Carduelis carduelis according to their migratory behaviour or geographic origin. We compared morphologic and isotopic variables between birds caught in two different obligatory migratory pathways (eastern and western border of the Pyrenees) and throughout the post-breeding period (from late summer to winter). The isotopic and morphological traits varied across seasons (from autumn to winter), indicating that birds captured later in the season had traits typical of longer-distance migrants that come from regions situated further north. Moreover, our results suggest that Goldfinches caught in the eastern and western borders of the Pyrenees slightly differ in body size and in one of the two colour patch-associated traits, but not in their flight apparatus or isotopic values, these last being more strongly related to their areas of origin. Such observed regional differences, therefore, may be more strongly related to other selection pressures. [ABSTRACT FROM AUTHOR]