Behavioural responses of breeding Silver Gulls to tourist traffic

Abstract

Ground-nesting seabirds are vulnerable to human intrusion which can potentially impair their breeding success. We examined whether tourist traffic on a boardwalk through a Silver Gull Larus novaehollandiae breeding colony affected the birds' behaviour sufficiently to potentially decrease reproductive success. Nest density was positively correlated with distance from the boardwalk. Gulls nesting ≤5 m from the boardwalk were more vigilant towards a stationary investigator than those further away. Tourists walking past breeding gulls stimulated a large increase in intra-specific aggression; stopping alongside parents with mobile chicks increased their intra-specific aggression even more. Larger tourist groups (≥3) stimulated more intra-specific aggression than smaller ones. An investigator walking past breeding gulls similarly stimulated an increase in intra-specific aggression, but the investigator's clothing colour, noise emission level and walking speed had no effect on the birds. An ambulatory investigat...