Epsilon Open Archive

Abstract

Where animals are and what they do, is the result of a continuous cost-benefit analysis of available alternatives. Choices have to be made, for example when settling in a breeding territory after migration, when foraging conditions change, when humans change the landscape, or when a predator approaches the nest. In this thesis, I used Eurasian curlew data to address these issues at the national, landscape and agricultural field level.
The results show that farmland was the most important habitat for the species (appr. four times as important as mires), but that < 40 ha patches of farmland embedded in forest landscapes were seldom used. During the first part of the breeding season, the birds preferred to forage on leys, but later they shifted to cereal fields. No effect of the construction of the Bothnia Line railway on Eurasian curlew densities could be shown. Finally, experimental approaches of nests showed that the chances for hatching success were best when the incubating bird leaved the nest neither very soon nor very late.
Albeit flexible in behaviour, Eurasian curlews seem to demand landscapes that contain sufficiently large patches of farmland, preferably with mixtures of fields under different management.