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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]

Woodlands subjected to commercial exploitation can play an important role in the conservation of forest-dwelling birds, whether these species breed, forage, or spend all or part of their annual cycle in this habitat. Since 2016, the Administration of Gipuzkoa Province, Spain, has implemented a new protocol designed to preserve the nesting habitat of the Red Kite (Milvus milvus) population breeding within the region. This species is locally classified as endangered and therefore has conservation priority. The aim of our study was to evaluate the efficacy, demographic impact, and cost of this protocol. Over a period of 7 yr (2016–2022), implementation of the protocol preserved 23 nests (i.e., 15.2% of the total 151 nests). From these protected nests, 37 young fledged, which was 16% of all the young fledged within the region in this period. Relative to the financial cost of protecting nature in Gipuzkoa, implementation of this protocol was inexpensive, totalling <0.1% of the administration's budget for managing natural habitats within the province. Los bosques sometidos a explotación comercial pueden desempeñar un papel importante en la conservación de aves que habitan en ellos y se reproducen, forrajean o pasan todo o parte de su ciclo anual allí. Desde 2016, la Administración de la Provincia de Gipuzkoa, España, ha diseñado e implementado un nuevo protocolo con el fin de preservar el hábitat de nidificación de la población de Milvus milvus que se reproduce en la región, ya que esta especie está clasificada como localmente en peligro de extinción y, por lo tanto, tiene prioridad de conservación. El objetivo de nuestro estudio fue evaluar la eficacia, el impacto demográfico y el costo de este protocolo. Durante un período de siete años (2016–2022), la implementación del protocolo preservó 23 nidos (es decir, el 15.2% del total de 151 nidos). De estos nidos protegidos, 37 crías emplumaron, lo que representó el 16% de todas las crías emplumadas en la región en este período. En relación con el costo financiero de proteger la naturaleza en Gipuzkoa, la implementación de este protocolo fue económica, totalizando <0.1% del presupuesto del departamento para la gestión de hábitats naturales en la provincia. [Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]

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]

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]

Volunteer-based (i.e., citizen science) monitoring schemes constitute a basic piece for the long-term monitoring of bird populations. This work aims to determine whether we can reduce the sampling effort, in terms of number of sampling journeys per yearly campaign, of a long-term breeding bird monitoring ringing scheme in Spain. With that goal, we test to what extent a progressive decreasing number of journeys (from the original effort of seven visits in a season to four visits) will have an impact on indices of adult abundance and/or productivity. Reducing the number of visits did not affect the estimate of abundance of adults, either if we consider a full-period population change index which takes into account the numbers of the last survey year in relation to the first one in the series, or if we consider annual trends (with a yearly index which is referred to a reference value—1—fixed for the first survey year). By contrast, the estimation of productivity was severely affected by a reduction of the sampling effort. We attribute this result to the fact that juveniles were captured late in the season and, therefore, eliminating the last sampling journeys produced biased estimates. It is proposed that the program can reduce the effort from seven to six visits (i.e., one visit per fortnight from May to July) with little impact on the estimation of abundance and productivity. Additionally, the program may admit sites with a sampling effort of four visits, from May to June, useful to estimate trends on abundance of adults and their survival rates (but not on productivity). With this dual option, we expect to increase the spatial coverage of the program and the robustness and representativeness of at least two of the indices calculated through the program, since we might both increase the number of participants (i.e., sites) and the type of habitats covered. [ABSTRACT FROM AUTHOR]

Artificial food subsidies like landfills generate very strong impacts on animal ecology and spatial behavior. Landfills indeed have been considered to be one of the most influential factors explaining the very fast recovery of many colonial waterbird populations worldwide, as documented for the white stork Ciconia ciconia. More recently, the increase of rice fields in some regions have also been argued to be part of an influencial process underlying the spatio-temporal distribution patterns of this species over many areas in southern Europe. It remains unknown whether these two habitat factors play an important role at explaining the spatial distribution pattern of the white stork and, more particularly, whether colony funding or colony size is dependent on them. Using data from a census conducted in 2018, we aimed to assess the effect of distance to a landfill or to rice fields, among other habitat factors, on the breeding colony size of a white stork population in northern Spain. Larger colonies were more likely to appear in trees or cliff, but less likely in buildings or other artificial substrates. They were also significantly more likely with decreasing distance to landfill, and when the habitat was dominated by dry cropland and meadows close to water bodies. Rice fields did not seem to have any significant effect. Our findings fit with those from other regions in Europe, and highlight the effect landfills have on population dynamics and spatial ecology for those species which are able to feed on this type of food subsidy. Our results also show that the main habitat cover over large geographic scales still plays a role independently of landfills. The European agricultural policies associated with the type and management of crops, and the Common Agricultural Policy in particular, will still have a decisive role for the species. [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]

In colonial seabirds, the nest substrate that is available and, in particular, the vegetation cover around the nest, are important environmental factors that drive an individual's nesting selection process and, ultimately, reproductive performance. Using data collected during three consecutive years in a Yellow-legged Gull Larus michahellis colony from the Bay of Biscay, Spain, we tested whether clutch size, egg volume, and hatching success covaried with the proportion of vegetation cover around nests. We found no effect of vegetation cover on breeding performance. Laying date showed a positive effect on egg volume and a negative effect on hatching success and the number of hatched eggs. Egg volume tended to be smaller in 2020 compared to 2018 and 2019, and hatching success decreased through the sampling period, with the lowest hatching success occurring in 2020. Our findings agree with a previous study in which vegetation had no or unclear effects on breeding performance in Yellow-legged Gulls; however, they contradict other seabird studies that found a positive correlation between the two variables. The role of vegetation on breeding performance could vary not only between gull species, but also geographically, with ecological drivers such as intra- and interspecific interactions and climate playing key roles in observed differences. Finally, the use of egg volume and hatching success as proxies for breeding output could be used for the long-term monitoring of the relationship between breeding performance and factors such as landfill management, fishing, or climate change in the Yellow-legged Gull and other gull species. [ABSTRACT FROM AUTHOR]

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Dredging and/or dumping actions at coastal environments are a common phenomenon worldwide. The re-working of dumped sediments from their disposal sites to places of great ecological value can have a very strong impact on the ecosystems through deep changes over the communities and the trophic web. Using a relevant dredging-dumping episode carried out in 2003 at Urdaibai, one the chief estuary areas in northern Iberia, we tested the consequence of this action on the subsequent use of the zone by shorebirds. The surface sediment characteristics before and after the dredging and dumping actions were also compared. The dredging at Urdaibai showed a negative effect on bird abundance in three out of the eight species tested overall (dunlin, grey plover, common ringed plover). Highest-ranked models supported a decrease in their population sizes two years after the event. In this scenario, local authorities should be appealed to take dredging and dumping effects into account in order to improve the estuary management. [ABSTRACT FROM AUTHOR]

The development of increasingly small devices for the satellite tracking of small birds allows us to explore aspects of avian migration that have never been studied before. Here, we provide the results of using 12- and 9.5-g platform transmitter terminals (PTTs) to track game birds of 300-385 g. Attaching PTTs to 20 Woodcocks ( Scolopax rusticola), wintering in Spain from 2006 to 2012, allowed us to explore (1) migration strategies (timing, velocity and stopovers), (2) the identity of the breeding grounds; (3) inter-year site fidelity to wintering grounds. We provide details of the route, speed and timing of migration and the location of remote breeding sites that were unknown prior to this study. The departure from winter quarters (median date) was completed by 20 March. The spring migration period lasted 40 days, and our birds were found to travel from >5,000 to >10,000 km, with a mean total migratory speed (i.e., including stopovers) of 170 km/day. Woodcocks followed fairly direct routes of migration. Stopover duration tended to be shortened when birds were closer to their breeding areas, which were located further east than previously stated. The only bird that provided long-term data (>1 year) was observed to return to the same wintering area, suggesting high winter site fidelity. The use of small PTTs opens new research lines related to the study and management of small to medium-sized migratory birds. [ABSTRACT FROM AUTHOR]

The movements of Mediterranean Yellow-legged Gulls Larus michahellis michahellis to the Bay of Biscay were analysed using sighting data of colour-ringed birds. A total of 1,270 sightings corresponding to 567 individuals was compiled over a 14-year period. Gulls originated mainly from colonies in the east of Iberia (52.7%), southern France (28.2%) and the Balearic Islands (17.3%). The proportion of the year spent in the Bay of Biscay decreased with age: first-year birds occurred on the coast of the Bay of Biscay throughout the year while older individuals were seen only from July to December. Overall, 39.7% of the birds were resighted in more than one calendar year. The return rate of adults and sub-adults was similar. The results confirm the importance of the Bay of Biscay as a non-breeding area (mainly in autumn and winter) for Yellow-legged Gulls from the Mediterranean, and suggest that this population should be considered as partially migratory. [ABSTRACT FROM AUTHOR]

The article discusses a study on the movements of first-year Yellow-legged Gulls or Larus michahellis lusitanius from the southeastern Bay of Biscay. It cites the use of darvic rings which allow researchers to conduct a more detailed analyses on movements of large gulls with consideration on the maximum distance where each individual was sighted. It suggests that a precise data on distribution of food availability can lead to a better understanding of the seasonal geographic distribution patterns of Yellow-legged Gulls in the southeastern Bay of Biscay.

The article discusses a study on the patterns of migration and wintering of European Robins Erithacus rubecula in northern Iberia, Spain focusing on seasonal patterns of captures and the relationship among migrating and wintering Robins, age and sex ratios and biometrics, fuel load and body condition. Robins were mist-netted weekly from July 2004 to May 2005 and data from robins trapped between September and April were considered. It suggests that the Robins are either birds moving at short distances or at migrating in short steps at longer distances.

The article discusses a study that determines whether plumage coloration is a valid criterion for defining and identifying White-throated Dipper types and its distribution in Spain. It refers to two types of White-throated Dipper existing in Spain, the Cincluse cinclus (C.c.) in the northwestern and central regions and C.c. aquaticus in the eastern and southern regions. Dippers were captured with mist-nets in ten representative zones within the Dippers' range in Spain. It suggests that plumage features alone cannot determine these birds.

Simple Summary: Alteration of natural habitats due to urbanization is an increasing concern worldwide. Some species, including owls, can exploit this novel environment, although the consequences at the population level have not been described. In this study, we analyze the effect of different urban variables on tawny owl (Strix aluco) population abundance. At the local scale, forest and urban cover, as well as the clumpiness index, affected tawny owl abundance. At the landscape scale, its abundance decreased in complex-shaped urban patches and when distance between them was greater. Urban habitats do not substitute natural habitats in terms of abundance, but the species can easily colonize patchy urban habitats. Natural habitats are being altered and destroyed worldwide due to urbanization, leading to a decrease in species abundance and richness. Nevertheless, some species, including tawny owls, have successfully colonized this novel habitat. Consequences at the population level have not been described; thus, our main objective was to describe the effects that urban structure have on the tawny owl population at local and landscape levels. Data were obtained from 527 survey points over 7 months in a large-scale owl survey in the Basque Country (northern Spain) in 2018. At the local scale, the interaction between forest and urban cover affected tawny owl abundance, the optimum being in medium forested areas. The interaction between urban cover and clumpiness index (urban patch distribution) showed a generally negative effect. At the landscape scale, its abundance decreased in complex-shaped urban patches and when distance between them was greater. In conclusion, at the local scale, when a minimal forest structure is present in urbanized areas, the species can exploit it. At the landscape scale, it prefers smaller urban towns to cities. Thinking ahead, the current tendency toward "green capitals" should benefit tawny owl populations. [ABSTRACT FROM AUTHOR]

Stable isotopes analyses (SIAs) are an efficient tool to obtain a general insight into the diet of generalist consumers, such as the Yellow-legged Gull (Larus michahellis). Here we analysed δ(13)C, δ(15)N and δ(34)S values in feathers of chicks and adults, and used Bayesian triple-isotope mixing models to reconstruct the diet of a Yellow-legged Gull population breeding in the southeastern Bay of Biscay. Questions to test were (1) whether adults and chicks rely on different feeding resources during breeding period; (2) whether there is a seasonal foraging effect involving a higher proportion of refuse food in winter compared to summer, and (3) the magnitude of the annual variation in diet. Prey consumption differed between colonies, among years, and also varied slightly between seasons, and this was mainly due to a differential use of prey of marine origin. However, diet did not differ between age classes. These results suggest a relatively monotonous diet with only slight variations from year to year, seasonally and at a local geographic scale., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Crimean-Congo hemorrhagic fever virus was detected in ticks removed from migratory birds in Morocco. This finding demonstrates the circulation of this virus in northwestern Africa and supports the hypothesis that the virus can be introduced into Europe by infected ticks transported from Africa by migratory birds.