Beach Attendance in Magellanic Penguins Spheniscus magellanicus

Seabirds depend on a variety of terrestrial habitats during the part of their life cycle that they spend on land. Understanding the temporal patterns of use of these habitats provides insights into their ecological requirements, and ultimately helps to direct efforts that ensure the birds' protection. We investigated Magellanic penguin Spheniscus magellanicus beach attendance at Punta Tombo, Argentina, during three breeding seasons to understand the use of beach habitat by juveniles and adults in the breeding season, during the day and in response to physical stressors. We found that beaches at the breeding colony are actively used during the breeding season. The number of penguins on the beach increased as the breeding season progressed for both juveniles and adults, but their patterns of beach use differed. Juveniles arrived later in the season and their numbers on the beach reflected their moulting cycle. In all three years, juveniles left the beach in late January, consistent with their pre-moult foraging trip. Adult penguins, on the other hand, attended the beach in larger numbers during hot days, suggesting that breeders used the beach to avoid high inland temperatures. More penguins, both juveniles and adults, were on the beach during the afternoons, which probably reflects their foraging pattern. However, juvenile counts were less variable between mornings and afternoons than adult counts, indicating a more even use of the beach by juveniles. Beaches provide an alternative habitat for several key functions throughout the life cycle of Magellanic penguins but the birds' temporal patterns of attendance probably depend on their age and breeding status and on the ambient temperature. Our study highlights the importance of the beaches surrounding Magellanic penguin colonies and provides guidance for the spatial layout of reserves where penguin colonies occur.