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The dynamics of migratory populations at wintering quarters can inform on population state and size because these areas act as demographic funnels, assembling birds from different origins. Previous evidence on survival probability of woodcock Scolopax rusticola wintering in northern Spain suggested a high harvesting pressure, but whether this pressure is causing a decline of woodcock occurrence at wintering quarters is still to be assessed. We used data from 3411 surveys conducted during the winter at 434 selected grasslands in the Gipuzkoa region, Northern Spain, to investigate the dynamics of woodcock occurrence probability, conditional on detection, over a period of 10 years (2009–2019). A 47% of the variation in woodcock occurrence within and across winters was explained by the monthly average minimum temperature. The remaining variation was due to a marked increase during the winters 2016 and 2017, contrary to the progressively decreasing values detected in previous years. At present, these abrupt yearly fluctuations prevent clear predictions on woodcock presence in the Gipuzkoa region. Future studies should explore woodcock occurrence probability according to scenarios of climate and habitat changes. [ABSTRACT FROM AUTHOR]

The main goal of this study was to describe in detail the structure and phenology of flocks of the Common Linnet (Linaria cannabina) passing through eastern Spain. Data were compiled during the spring and autumn migrations of 2019 to 2021 (excluding spring 2020), by counting and by capture for ringing. We counted 6151 flocks, comprising 17 732 birds, of which 7638 individuals were captured. The size of flocks ranged from 1 to 30 Linnets (mean ± 95% CI, 2.8 ± 0.1), with a higher proportion of solitary migrants in spring (46.8%) than in autumn (33.8%). Passage in spring peaked during the third hour after dawn, whilst in autumn this peak was just after dawn. There were more females than males (56%), probably as an indicator of latitudinal differential migration. Juveniles were significantly more abundant (c. 80%) than adults. The phenological pattern of the passage was more variable in spring than in autumn, and such variation could be useful to explore potential impacts of climate change on the migration ecology of the species. [ABSTRACT FROM AUTHOR]

Crossbills (Loxia spp.) provide a classical avian model of ecological specialization on food resources. Previous studies have suggested that morphometric, genetic and vocal diversification among Common Crossbill Loxia curvirostra populations is better explained by ecological distance (use of different conifers) than by geographical distance, indicating that populations have diverged adaptatively. We tested for adaptive divergence in Iberian crossbills using bill and body size measurements of 6082 crossbills from 27 sites, each consisting of a dominant or single pine (Pinus) of four possible species. Crossbills using different pines differed significantly in body size and bill size and shape. There was no correlation between geographical and morphological distance among sampling sites, consistent with the hypothesis that the morphological divergence of Iberian crossbills is shaped by their ecological differences (foraging on alternative conifers) rather than geographical distance. However, for unknown reasons, Common Crossbills foraging on Pinus sylvestris in Iberia have on average much smaller bills than Parrot Crossbills Loxia pytyopsittacus feeding on the same pine species in northern Europe. The extent to which crossbills specialize on Iberian P. sylvestris remains to be established. Specialization on conifers with overlapping geographical distributions may be facilitated by matching habitat choice of crossbills as a function of their local intake rates. [ABSTRACT FROM AUTHOR]

Background: The dynamics and structure of many bird communities are changing due to the global warming and changes in the land use and management. The Ebro Valley constitutes one of the chief wintering areas for several passerine species in Iberia, and the reed beds spread across this Valley concentrate huge numbers of birds that use them to roost, while the surrounding agricultural areas serve as main foraging habitats. The aims of this work are (1) to quantify how variable a non-breeding passerine bird community associated to a reed bed area in the Ebro Valley is, and, (2) to test for the effect of weather on possible annual fluctuations in species' proportions at a regional/local scale. Methods: We used for that ringing data collected at Badina de Escudera lagoon (Navarra) over a 12-year period. Results: Though, overall, the assemblage did not vary strongly among years (most similarity values were > 0.8), we still found a significant linear effect of year on the proportion of captures of Reed Buntings (Emberiza schoeniclus), i.e., the dominant species detected in our passerine community. The increasing loss of weight of Reed Buntings in the community was due to a progressive decrease in its abundance. Conclusions: The structure and diversity of passerine community in Badina Escudera was not influenced by meteorological conditions at a local scale, suggesting that local weather would not have an impact on numbers of Reed Buntings in winter. [ABSTRACT FROM AUTHOR]

Transients can have a severe impact on demographic parameter estimates. For instance, the use of visual counts or number of captures at a ringing station to assess indices of abundance may result in biased over-estimates due to the presence of transients. With the aim of contributing to understand transient dynamics within the Eurasian breeding passerines, we used data collected at a ringing station (2010–2018) in a reed bed area of northern Spain designed to sample breeding reed warblers Acrocephalus scirpaceus. Specifically, we tested for the effect of season on the proportion of transients and explored for correlations of rainfall regimens at both the winter and breeding quarters on annual fluctuations of the proportion of transients. The proportion of transients was not constant across the season; it showed relatively small values until mid-June, coinciding with arrivals from Africa and the peak of the breeding period, and then increased very steeply (means > 60%) already in July, with even ca. 90% of transients captured during the second half of July, coinciding with an influx of birds that would be already passing through the area en route to winter quarters in Africa. Analyses to estimate population trends of breeding reed warblers should take this circumstance into account; otherwise, models may show odd patterns, due to a mixture of local and non-local population that might show dissimilar demographic trends. Limiting data analyses to the breeding sub-period having a lesser amount of transients is recommended. Annual fluctuations in the proportion of transients did not correlate with any of the rainfall values in Africa (winter quarters) or meteorological conditions in Europe (NAO index; rainfall values at a local level), though it might be that we did not choose the appropriate variable/period/location combination. Our data set was relatively small; hence, this may hamper us to detect weak linear trends. Future research should contribute to answer this question and deep into the factors driving transience dynamics in bird populations. [ABSTRACT FROM AUTHOR]

The ecology of opportunistic foragers can be highly dependent on anthropogenic food sources, such as landfills, resulting in changes in several ecological and demographic aspects. The total closure of several landfill sites and the use of deterrence systems to prevent access to the remaining open landfill sites in a region in the northern Iberian Peninsula provided an excellent opportunity to evaluate the consequences of landfills on the trophic ecology of an opportunistic forager, the Yellow‐legged Gull Larus michahellis, using these resources. Based on stable isotope analyses, we used mixing models to estimate changes in diet before and after the closure of the majority of landfills in the breeding and the non‐breeding season. We found a decrease in the consumption of food from landfills after their closure, which was accompanied by an increase in feeding on terrestrial prey (mostly earthworms), but only in the breeding season. Interestingly, we observed no increase in marine prey consumption after the landfill closures. In winter there was a decrease in terrestrial prey consumption, whereas the consumption of marine and, despite their reduce availability, landfill resources increased. Thus, and unlike when all the landfills were open, we detected significant trophic differences between breeding and non‐breeding seasons. Additionally, we found significant trophic differences among colonies that were quite close to each other, but not between breeding adults and chicks. In conclusion, landfill closure or the use of deterrence systems had a direct impact on the trophic ecology of Yellow‐legged Gulls; loss of refuse was mainly compensated for by prey of terrestrial origin when breeding, but not in winter. Thus, this species may experience foraging constraints in winter with potential effects on other life‐history aspects including their dispersal, breeding and survival that needs further evaluation. [ABSTRACT FROM AUTHOR]

Measures of species co-occurrence, as a proxy of biotic interactions, may be as important as environmental factors when explaining the distribution of many species. We assessed the relative effect of both species co-occurrence and environmental factors in predicting the occurrence (presence/absence) of woodpeckers and passerines in mature forests of the Northern Iberian Peninsula. We hypothesized that woodpecker occurrence would affect the occurrence of passerines. We calculated the occurrence of woodpecker species using models that included environmental factors aggregated at three spatial scales (200, 500 and 1,000-m2). The occurrence of passerine species was then modelled by using either species co-occurrence (including the occurrence of woodpecker species) or environmental factors at the 200-m2 cell scale. The occurrence of five out of nine passerine species was best explained by the co-occurrence of woodpeckers alone, whereas the occurrence of the remaining passerines was best explained using a combination of species co-occurrence (i.e. woodpeckers and/or other passerines) and environmental factors. In Southern Europe, woodpeckers are expanding their distribution in line with forest maturation, and this could increase the diversity of bird communities in forest systems. [ABSTRACT FROM AUTHOR]

The relative importance of biotic and abiotic variables on the Common Kingfisher Alcedo atthis breeding distribution in northern Iberian rivers was quantified through surveys completed in 2007. Eight rivers were surveyed for "positive" and "negative" (control) breeding territories (PBT and NBT, respectively). PBT (N=9) were 3-km river sections with breeding pairs; NBT (N=8) were 3-km river sections close to PBT, where no pairs were found, with apparently similar features to the PBT and one or more cut banks suitable for nesting. Stepwise discriminant analysis (SDA) correctly classified 94.1% of territories and revealed PBT was associated with higher oxygen concentrations, a lower maximum depth and lower proportion of rockfills. Causes and consequences of these findings are discussed. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the relationship between breeding, moulting and fuel load of Common Crossbills Loxia curvirostra curvirostra inhabiting a Scots pine Pyrenean forest. Data were collected from two locations (Sierra de Uztarroz and Bigüezal) in northern Iberia by systematic mist netting between 2000 and 2008. Breeding females were detected in most months of the year except June, October and November, and with two main peaks, one in late winter (March), and another in the summer (August). Between years, reproduction was more variable in some months than in others, particularly in summer months. This suggests that breeding during the summer was more likely to be influenced by external factors and relatively opportunistic compared to winter breeding. Moulting adults of both sexes were captured during almost every month with a unimodal pattern peaking in June, similar to the pattern described for Mediterranean Crossbills. Moulting did not overlap with breeding, and our data do not support suspended moult patterns. Mean fat scores overall were low and, as was the case for body mass, showed little month-to-month variation. [ABSTRACT FROM AUTHOR]

The article discusses research done on the timing of passage of migratory Blackcaps, also known as Sylvia atricapilla, in Iberia, Spain. The researchers examined age variations of flight-associated morphology and analyzed ring-recovery data. Blackcaps with pointed and longer wings were captured during autumn season. The researchers also discovered the higher abundance of Blackcaps from Ireland and Great Britain as compared to those from mainland Europe. Mist nets were used to capture study subjects during the spring and autumn migration period.