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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]

The Bay of Biscay is an important non-breeding area for some Palaearctic gull species and populations. The aim of this work is to describe the spatial and temporal distributions of non-breeding gulls in the Bay of Biscay, and to identify their major areas of origin. With that goal, we analysed 6773 live sightings of colour-ringed gulls within the southeastern part of the Bay of Biscay during the 20 years 2000–19, relating to 2552 individuals of 10 species. Their distribution along the coast was not homogeneous, with numbers peaking in most cases from November to February, though some species were observed to peak around midsummer. Their origins comprised a wide geographical area encompassing western and eastern Europe; overall, the species can be divided into four groups by origin: northwestern France with Britain and Ireland, central western Europe (with a centroid in the Benelux region), eastern Europe, and the western Mediterranean. [ABSTRACT FROM AUTHOR]

Determining the age of specimens is of great help in wildlife management, especially for rare or threatened species in which each individual has a high value. In birds, differences in moulting pattern between juveniles and adults may in some cases allow determination of a bird's age from the examination of its plumage. In the present study, we analyse the moult of 19 breeding individuals of White-backed Woodpecker Dendrocopos leucotos lilfordi captured for GPS tagging in the Pyrenees, in order to describe, for the first time, the moulting pattern of this endangered woodpecker. Two well-differentiated groups of adult birds were identified: those that underwent a partial moult, and were classified as second-calendar-year birds, and those that performed a complete one and were classified as older. The first group had renewed most lesser and median coverts, all primaries and the innermost greater coverts, thus showing clear moult limits between the primaries and secondaries and within the greater coverts. Some individuals also replaced up to two more greater coverts (GC5–6). Individuals classified as older birds showed all feathers to be of a single generation, indicating that they had undergone a complete moult. A few individuals in this category retained a few unmoulted secondaries and primary coverts, however. A recapture of a bird with a complete moult, which had been captured a year before showing a partial moult, would confirm these moult sequences to be age dependent. This moulting pattern is very similar to that described for other spotted woodpeckers, and allows researchers to determine the ages of breeding individuals during the nesting season. [ABSTRACT FROM AUTHOR]

During the winter, Bramblings Fringilla montifringilla are known for concentrating in huge communal roosts, normally situated along a NE–SW axis from west Russia to France in southern Europe. Irruptions of Bramblings in Iberia are rare and normally only in an attenuated form. Exceptionally, in November of 2010 a large roost of c 900,000 Bramblings formed in the Basque mountains of northern Iberia. We caught and ringed Bramblings from this roost from November 2010 to February 2011, and compared age and sex ratios, wing length and body mass to data reported in the literature. Overall, first-year birds comprised more than half the roost and the sex ratio in first-year birds was biased to females. This is in agreement with the prediction that first-year birds and females migrate to regions further south than males and adult birds. Wing length was constant across the season, but not body mass. Body mass was also negatively correlated with temperature and positively correlated with snowfall. [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 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.