Morphological changes in European goldfinches (Carduelis carduelis) released by bird trappers
In Spain, several Autonomous Communities have granted licenses to capture European goldfinches (Carduelis carduelis parva) during the post-breeding period, from August to December. In Galicia (NW Spain) and other Autonomous Communities, after 5–7 months of captivity, many
birds are released. We tested the hypothesis that captivity results in biometric and body condition changes which affect the post-release survival of these birds. We used two groups captured in Galicia, the first made up of birds captured for ringing and the second consisting of birds captured
by bird-trappers, kept in captivity for 5–7 months and then released. Two-way ANOVA tests were used to test the effect of group and sex on the wing, bill, head, tarsus and tail measurements. Birds held in captivity had shorter wings and longer bills than those captured for ringing. The
significance of these morphometric changes is unknown but it is possible that they could have a detrimental effect on foraging behaviour and post-release survival. In light of this, those involved in keeping wild birds in captivity should review their husbandry techniques.