First exploration of the feeding areas of Brown Skuas during the incubation stage at Islas Blancas, Chubut

The Brown Skua (Catharacta antarctica) occupies an important position in the marine ecosystem, functioning like opportunistic predator, scavenger and kleptoparasite. To date, very little is known about its trophic ecology on the Patagonian coast. To evaluate the patterns of use of feeding areas during the incubation period, a total of 10 global positioning system loggers were deployed on incubating adults during the 2016 breeding season. A total of 104 foraging trips were recorded, 70% of which were performed in daylight hours. On average, each bird performed 2 trips per day (range: 1-5). The average distance traveled in foraging trips was 44.5 ± 36.4 km (range: 0.7-472.0), with an average duration of 110 ± 67 minutes. The feeding areas were located at 13 ± 10 km from the nests, all located at-sea and mainly to the east of the colony. The total feeding area used by the skuas was 1173 km². This is the first study on the spatial ecology of skuas in Patagonia and shows that at least during incubation, Brown Skuas from Islas Blancas obtain their food at sea. These results show the importance of waters surrounding the colony in the trophic ecology of the species and suggest the need for further studies to assess if Brown Skuas maintain this feeding strategy during other stages of the reproductive cycle.