Distribution maps and minimum abundance estimates for wintering auks in the Bay of Biscay, based on aerial surveys

The “Erika” oil spill has killed more seabirds than any before in Europe: nearly 70 000 guillemots (Uria aalge) were found dead or alive on beaches, and many more are thought to have been killed. This unexpectedly high number highlighted how poor our knowledge was on spatial and temporal patterns in seabird distribution in the Bay of Biscay. The purpose of our research project, “ERIKA-Avion”, was to fill this gap, providing the first distribution maps and abundance estimates of seabirds wintering in the entire shelf of the Bay of Biscay. In particular, we analysed fine-grained distribution maps for the wintering auks, comparing their areas of highest density with the oil drift area, and proposing for the first time (although preliminarily) minimal abundance estimates for these birds in this area.