NEST CONCEALMENT AND ITS RELATIONSHIP TO PREDATION

GANDINI, P.; E. FRERE AND D. BOERSMA

ORNITOLOGIA NEOTROPICAL

NEOTROPICAL ORNITHOLOGICAL SOC

Año: 1999 vol. 10 p. 145 - 150

1075-4377

This paper analyses the effects of nest-site characteristics on reproductive success of the Magel-lanic Penguin (Spheniscus magellanicus) during five breeding seasons at Cabo Vírgenes (52°20´S, 68°21´W) on the Patagonian coast of Argentina. During three out of five breeding seasons egg losses were lower in nests with high cover than in low cover. Mean fledging success was greater in high than in lower cover nests. An experiment performed with abandoned eggs placed in empty penguin nests showed: 1) Eggs placed in nests with high cover were less likely to disappear than those in nests with little cover, 2) Egg losses were higher in nests located in peripheral areas than in central ones, and 3) Egg losses were lower in nests with high cover than low cover in both central and peripheral areas. Most nests were orientated against prevailing winds. Our results suggest Magellanic Penguins are selecting nest entrances to minimize heat loss and to reduce their energy budget. We designed a nest quality index with the variables interpreted as important by a multivariate analysis (Principal component analysis). The result showed that the most successful nests were situated under tall bushes with high cover at the roof and to the south and were located close to other nests. This could be the result of an anti-predation strategy where the prey selects concealment of the nest in preference to self-defense against predators.(Spheniscus magellanicus) during five breeding seasons at Cabo Vírgenes (52°20´S, 68°21´W) on the Patagonian coast of Argentina. During three out of five breeding seasons egg losses were lower in nests with high cover than in low cover. Mean fledging success was greater in high than in lower cover nests. An experiment performed with abandoned eggs placed in empty penguin nests showed: 1) Eggs placed in nests with high cover were less likely to disappear than those in nests with little cover, 2) Egg losses were higher in nests located in peripheral areas than in central ones, and 3) Egg losses were lower in nests with high cover than low cover in both central and peripheral areas. Most nests were orientated against prevailing winds. Our results suggest Magellanic Penguins are selecting nest entrances to minimize heat loss and to reduce their energy budget. We designed a nest quality index with the variables interpreted as important by a multivariate analysis (Principal component analysis). The result showed that the most successful nests were situated under tall bushes with high cover at the roof and to the south and were located close to other nests. This could be the result of an anti-predation strategy where the prey selects concealment of the nest in preference to self-defense against predators.