Uria aalge

Around 800 to 900 pairs of common guillemots nest in colonies on Brittany’s steep cliffs. The single egg is tapered to reduce the risk of rolling over the narrow rocky ledges. Guillemots generally fly low over the water, flapping their wings rapidly. They capture their prey by diving, night and day, to depths of up to 40m. Northern European guillemots migrate south in winter, and the species is widespread in French waters in the English Channel and Atlantic. Guillemots are often seen very close to the coast during winter storms.

The species is threatened by oil pollution, bycatch, predation and possibly by the reduction of its food resources. Very little is known about their breeding and wintering distribution at sea in France.

Like penguins, guillemots nest on steep cliffs that are difficult to access. For this reason, and to avoid disturbing the colonies, we capture adults who are not on their nests but resting at sea or on rocky islets on the edge of the Sept-Iles National Nature Reserve colony.

To discover the movements of wintering guillemots along the French coast, individuals are captured in winter directly at sea in sheltered gathering areas such as the Brest roadstead.

A few individuals brought to care centers, often after winter storms, may also be fitted with GPS before being released.

The guillemots are equipped with OT10-D GPS beacons, which have the particularity of being adapted to the dives and allow the recording of the pressure and therefore the depth of the dives. These small 10g beacons transmit data regularly via 3G and are attached to the feathers on the bird’s lower back with special tape. The beacons fall off after a few weeks or months as the tape wears down or the feathers moult.

Migratory in France

Breeder in France

: Wintering in France