Age-dependent differences in iris colouration of passerines during autumn migration in Central Europe.

Avian eye colour changes with age, but many aspects of this transition are still insufficiently understood. We examined if an individual's sex, age, species and body condition are related to the iris colour in common migratory passerines during their autumn passage through Central Europe. A total of 1,399 individuals from nine numerous species were ringed and examined in late autumn in northern Poland.

Does the sex and age of birds and the size of human settlements affect recapturing of the Great Tit (Parus major) at bird feeders?

Urban and rural habitats provide different conditions to wintering birds mainly due to different access to bird feeders. Returning to the food sources, even under the stress related to trapping, could play an important role in the energetic budget of wintering birds. We studied the duration of period between the first and the second capture of the Great Tits (Parus major) caught and ringed at bird feeders.