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

Piotr Skórka,William J Sutherland,Magdalena Lenda

doi:10.1007/s10980-016-0382-x

Abstract

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. 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. We surveyed 61 fish ponds (foraging patches) in southern Poland and counted Caspian gulls. 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. 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.

Highlights

Dispersal is a key process affecting the local population dynamics, patch occupancy and metapopulation functioning (Paradis et al 1998)
Juvenile birds responded at finer spatial scales to the factors than did adults
The abundance of juvenile birds was mostly correlated with the landscape composition

Summary

Introduction

Dispersal is a key process affecting the local population dynamics, patch occupancy and metapopulation functioning (Paradis et al 1998). Juvenile dispersal has important consequences for population dynamics, the post-fledging period is perhaps the least studied and least understood part of the avian life cycle (Kershner et al 2004) This period is critical for animals (Paradis et al 1998, 1999): juveniles must cope with novel environments, compete with more experienced adults for resources and, as a probable consequence, usually have lower survival rates than adults (Greenwood and Harvey 1976). The most crucial problem for juvenile birds at this time is to find sufficient food resources so as to survive over the winter (Szostek and Becker 2015)

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