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Response of young and adult birds to the same environmental variables and different spatial scales during post breeding period

Skórka, Piotr, Lenda, Magdalena, Sutherland, William J.
Landscape ecology 2016 v.31 no.9 pp. 2063-2078
Larus, age structure, birds, breeding, environmental factors, environmental impact, fish, fish ponds, foraging, habitats, juveniles, landscapes, learning, social behavior, young adults, Poland
CONTEXT: How do young birds achieve spatial knowledge about the environment during the initial stages of their life? They may follow adults, so gaining social information and learning; alternatively, young birds may acquire knowledge of the environment themselves by experiencing habitat and landscape features. If learning is at least partially independent of adults then young birds should respond to landscape composition at finer spatial scale than adults, who possess knowledge over a larger area. OBJECTIVES: We studied the responses of juvenile, immature and adult Caspian Gull Larus cachinnans to the same habitat and landscape variables, but at several spatial scales (ranging from 2.5 to 15 km), during post-breeding period. METHODS: We surveyed 61 fish ponds (foraging patches) in southern Poland and counted Caspian gulls. RESULTS: Juvenile birds responded at finer spatial scales to the factors than did adults. Immature birds showed complicated, intermediate responses to spatial scale. The abundance of juvenile birds was mostly correlated with the landscape composition (positively with the cover of corridors and negatively with barriers). Adult abundance was positively related to foraging patch quality (fish stock), which clearly required previous spatial experience of the environment. The abundance of all age classes were moderately correlated with each other indicating that social behaviour may also contribute to the learning of the environment. CONCLUSIONS: This study shows that as birds mature, they respond differently to components of their environment at different spatial scales. This has considerable ecological consequences for their distribution across environments.