Títol Different winter strategies in a group of siskins (Spinus spinus) in a wintering quarter in southeastern Spain

Autors Jana Marco Tresserras , José Luis Cantó Corchado , Alejandro Alamán Requena , Miryam Palomo Sepúlveda

Període de realització 2005 - 2018

Resum Winter quarters have an important role on individual fitness and survival rates when food availability become scarce at the breeding sites. During harsh winter, good knowledge of the area, location of resources and retention of good quality territories can become critical to ensure survival of the winter bird population, having even an effect on sexual selection and reproductive success at the breeding sites. For these reasons, strong fidelity to either a breeding or wintering area can be found in several bird species. In this study we examine differences in wintering strategies in Siskins (Spinus spinus), a typically nomadic species, through different winter seasons, in a wintering quarter at southeastern Spain. Since 2005 to 2018 we recorded 4 different massive irruptions of siskins at the study area located in Font Roja Nature Park, Alcoi (Alicante) (winters: 05-06, 14-15,15-16,17-18). A total of 508 siskins were captured and ringed. Following variables were record for each individual: sex, age, wing-length, tarsus, P3 length, weight, fat and muscle. In 2017-2018 winter, initial and last capture were also recorded for all birds, and P2-P10 lengths and molt extension were taken for 137 of 337 siskins captured. Our results show that sex ratio and age proportion changed gradually between winter irruptions. Sex-ratio: 50-50 to 20-70 (♀-♂). Age proportion: 20-70 to 50-50 (adult-juvenile). Using extensive data from winter 17-18, we compared wing-shape variation, moult extension of juveniles, sex-ratio, age proportion and body measurements between groups of siskins with different wintering strategies: resident (remain in a single wintering area) and transients (move continually throughout the winter), in order to understand the establishment of the groups in the area. Both groups showed similar sex and age proportions, but different extension of post-juvenile moult , different arrival dates to the study site and different fat accumulation the day of the first capture.