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Important biological parameters, such as movement and survival, can differ substantially between sexes, driving the demographic patterns of a population. Sex-dependent spatial segregation at the foraging grounds can evolve as a mechanism to reduce competition for resources between sexes, among other causes. Investigating such segregation, especially in scenarios of decreasing food availability, can contribute to understanding how birds adapt to a fast-changing world. The aim of the present study was to determine whether year-round movements and survival varied between sexes within a resident Yellow-legged gull Larus michahellis population. To this end we used live encounter data on colour-ringed Yellow-legged Gulls in northern Spain in the period 2009–2017. We used Generalized Linear Models to analyse distance to the colony of origin and multi-state models to estimate both survival and year-round movements, which did not provide evidence supporting an effect of sex on movement and survival. In contrast, distances travelled from the natal colony varied between seasons and all gulls were more likely to move greater than 100 km from natal sites. Juveniles showed lower survival rates (0.55) than older birds (0.90). Future research with GPS data might help to reveal, if existing, the occurrence of local spatial segregation between sexes that otherwise remains undetected. [ABSTRACT FROM AUTHOR]

The article details a study of the degree of connectivity in the Eurasian Reed Warbler, Acrocephalus scirpaceus, between breeding grounds (BG) in central and northern Europe and stopover areas in Iberia during the autumn migration. Among the methods used include biometric analyses for wing pointedness, and generalized linear model for checking the morphological variations between migratory regions. Researchers found a relatively low connectivity between BG in Europe and passage areas in Iberia.

The article discusses a study which examined the extent to which the coastal marshes of northern Iberia are used by the Common Kingfisher during the autumn migration period. Mist nets were used to capture Kingfishers at Jaizubia. To test for seasonal variation in body mass controlled for body size, the study adopted parametric procedures. Cormack-Jolly-Seber (CJS) models were used to estimate staying probability. Results of the study showed that peak passage occurred during late August and that 68% of within-season recaptures were obtained less than a month after the first capture event. The study also found no difference between sexes in timing of passage. According to the study, there was a positive correlation between change in body mass and minimum stopover duration.

The article discusses the impact of sampling frequency (SF) in determining differential timing of migration. Previous reports indicate that migration schedules were affected by age in autumn when adults migrate earlier and by sex in spring when males start earlier. The Blackcaps Sylvia atricapilla songbird was chosen due to the available numbers and the ease of determining age and sex. In the autumn of 2005 and spring of 2006, Blackcaps were marked in a 48-hectare area in Loza, Spain, that is used as breeding ground by local birds and as a stopover site by foreign birds. Results show that differential timing between sexes or age classes was detectable at certain levels of SF but not at lower SF. In spring, differential timing between age classes only became significant with daily sampling.

This article focuses on a study which explored environmental correlates of among-population phenotypic variation in Dipper morphology throughout Iberia. The study used a number of abiotic environmental factors including river slope, altitude, mean temperatures, and the amount of annual precipitation. Hierarchical Linear Mixed Models (HLMM) were also utilized to examine the effect of abiotic factors on biometrics. Results of the study showed that there was no correlation between age and tarsus length. It also found that the abiotic effect disappeared for relative and absolute wing length.