Factors influencing brown skua reproductive success at Elephant Island Antarctica

Abstract

The objective of the present study is to evaluate how some variables could influence breeding successes of Brown Skua (Catharacta lonnbergi) at Stinker Point, Elephant Island, Antarctica. Variables measured were Intra-specific Nearest Neighbour Distance (NND), Penguin Colony Distance (PCD) and egg laying date per breeding pair. Variables that could influence Chick Survival Probability were analysed through logistic regression (forward). Data was collected during the 2009/10 austral summer. The studied population consisted of 37 breeding pairs, from which 23.7% (n = 9) successfully raised chicks to fledging. NND and PCD significantly affected chick survival (Nagelkerke R2 = 0.21, p < 0.001 and Nagelkerke R2 = 0.54, p < 0.05, respectively), showing that chicks have lower survival probability among closer nests and among the nests that are near penguin colony. There is a positive and significant relation between NND and PCD (Linear R2 = 0.38, p < 0,001). There was no significant relationship between the chick survival and egg laying date. Analysis showed different tendencies from those presented in other studies where chick survival probability was lower in nests near the penguin colony and an early egg laying date did not reflect a higher chick survival probability as expected. The last one probably caused by severe weather during the beginning of the studied breeding season and many nests were covered by snow, which caused the loss of many eggs resulting in very low reproductive success.