Modelling the movements and fishing habitat of Great Cormorants

We study the movement patterns, fishing behaviour and habitat choice of Great Cormorants based on existing data from 25 birds marked with GPS-loggers. The aim is to reveal where the Cormorants prefer to fish, which is achieved by statistical analyses relating observed fishing sites to randomly chosen sites at corresponding distances from the places where the birds spent the night. We compare the fishing behaviour during and after breeding by examining the daily number of fishing trips, as well as the distances, durations, and numbers of dives per fishing trip. We also study the phenology of autumn migration, i.e., when (what dates) the Cormorants move away from Finnish waters during the autumn. The project produces new information on the basic ecology and fishing behaviour of Cormorants in Finland. Part of the results are directly applicable in various assessments and reports on how Cormorants affect commercial fisheries in Finland. For example, the distances between fishing sites and colonies, and how long the Cormorants stay at Finnish waters during the autumn, have direct implications for the number of fish consumed by Cormorants at different areas. The results will be published in a scientific peer reviewed journal.