Utilization of Guillemot Uria aalge colonies by Jackdaws Corvus monedula

TitleUtilization of Guillemot Uria aalge colonies by Jackdaws Corvus monedula
Publication TypeJournal Article
Year of Publication1974
AuthorsBirkhead T.R
JournalOrnis Scandinavica
Pagination - 71 - 81
Date Published1974
ISBN Number00305693
KeywordsAlca torda, Corvus, Corvus monedula, Uria, Uria aalge

Foraging activity of Jackdaws at a Guillemot colony on Skomer Island, Wales, is described. Colour ringing showed that only a few "specialist" Jackdaws operated at the Guillemot colony, and these fed mainly on fish dropped by Guillemots and on remains of Guillemot and Razorbill eggs predated by other species. Jackdaw success for collection of fish was 2.0% and overall food item success was 3.5%. Jackdaws were able to determine the level of fish being brought to the colony by Guillemots, and regulated their behaviour accordingly. Thus, when fish levels were high, Jackdaws increased the amount of time they spent at the colony, and by doing so, increased the number of food items they obtained. The results showed that Jackdaw activity did not seriously affect Guillemot breeding success.

Short TitleOrnis Scandinavica