Foraging-site fidelity in chick-rearing Magellanic penguins

BOERSMA, DEE; REBSTOCK, GINGER; GARCÍA BORBOROGLU, PABLO

Dunedin

Congreso; International Penguin Congress; 2019

University of Otago

When foraging on spatially predictable resources, animals should return to the same site to forage. When foraging on unpredictable resources, they should explore a variety of sites. To determine how foraging-site fidelity affects breeding success, we compared foraging-site fidelity within breeding seasons among Magellanic penguins rearing chicks at Punta Tombo, Argentina. Our index combined distance to the farthest point of each foraging trip and bearing to that point. The index comparing two trips ranges from -0.99 (foraging locations far apart) to 1 (same distance and direction). The mean of all pairwise comparisons for a penguin?s trips is the index for that penguin. Fidelity indices averaged 0.54 (range -0.10-0.90, n = 192). Penguins were more consistent in their directions (0.83, 0.2-0.98) than in their distances (0.26, -0.89-0.90). Penguins that were least faithful to foraging sites were likely to raise two chicks because they made short foraging trips (< 1 day) as well as longer, multiday trips. Penguins that were most faithful to foraging sites had a high probability of raising one chick. The probability of raising zero chicks did not change with foraging-site fidelity. The fidelity indices of penguins that made short trips were similar to those of penguins that made only long trips when we excluded short trips. Penguins that made short trips were not in better body condition than penguins that only made long trips. We found that penguins at Punta Tombo should have high site fidelity during multiday trips and make some short trips to raise two chicks.