The Turdus Project
One of the main goals of this study is to assess the potential connections between wintering site selection and breeding performance (carry over effects).
Redwings are mainly migratory and ringing recoveries indicate European wintering sites ranging from Britain/Ireland south to the Iberian Peninsula. However, a fraction of the population has become resident in Iceland with numbers reaching thousands in some years. According to yearly winter bird counts the number of redwings staying in Iceland over the winter is growing.
If winter site strategies are mainly inherited it can be presumed that breeding performance will be an important driver shaping frequencies of different strategies.
Risk factors with different winter site selection are for example, blood parasite abundance, food availability, long migratory routes, arrival time on breeding grounds.
Blackbirds (Turdus merula) where know in Iceland as fall and winter guests. From the year 1991 blackbirds have been breeding in Reykjavík, around the year 2000 there was a big influx of birds and the population has been growing ever since. They are thought to be sedentary in Iceland and in the winter counts 2016/2017 there where counted over 2000 birds.
Redwings breed up to three times per summer. Each breeding season they get a new partner but have the same partner during the whole season. Their normal clutch size is 3-5 eggs. The female lays on the eggs the entire incubation period but the male stays close to the nest. Both parents feed the chicks after they have hatched, while they are in the nest and also for a few days after they leave the nest.
Blackbirds breed up to three times per summer. Their normal clutch size is 3-5 eggs. The female builds the nest all by her self and she lays on the eggs over all of the incubation period. The male usually isn't seen close to the nest during the incubation period but he usually takes care of the chicks alone while the female gets ready for the next nesting period.