GPS and Time-Depth Recorder tracking of common and Brunnich's guillemots from five colonies around Iceland, June-July 2019-2021

We tracked 94 common and 50 Brunnich''s guillemots from five colonies around Iceland (Latrabjarg, Grimsey, Langanes, Skrudur and Papey) during late incubation and chick rearing from June to July 2019. We also tracked 5 common and 3 Brunnich''s guillemots from Langanes during chick-rearing in July 2020 (GPS only). Finally, we tracked 4 common and 4 Brunnich''s guillemots from Langanes during late incubation and chick rearing in June 2021. We used Pathtrack nanoFix GPS loggers to record locations every 3min and Cefas G5 TDR loggers to record depth every second. The tags recorded the birds'' behaviour for a few days (typically 2 to 3). The aim was to investigate the foraging behaviour of the two species and the potential competition between them. Funding was provided by NERC grant NE/R012660/1 (part of the NERC Changing Arctic Ocean programme).