Influence of the disturbance on shorebird behaviour

Abstract

Human disturbance is an issue affecting many animal species. The presence of perceived predators disturbs wildlife and may reduce foraging success and species abundance. Birds are a common focal group in studies of anthropogenic disturbance as they are at risk of increased exposure to human presence and activities. This can lead to decreased bird diversity and increased energetic costs. Humans that are accompanied by dogs pose a greater disturbance threat to birds. Species differ in their response to disturbances which influences flight-initiation distance (FID), site use and vulnerability to changing environmental conditions. Species may exhibit a certain degree of habituation to human presence but this does not alleviate the negative effects entirely. Estuaries are important habitats and resource providers for migratory shorebirds. Shorebirds using mudflats and estuaries as winter foraging grounds are experiencing high levels of human disturbance at these sites. This causes problems because of the constraints tidal fluctuations already place on foraging opportunities. This study investigated how anthropogenic and natural disturbances are affecting birds at two estuarine sites, the Douglas Estuary and Harbour View Beach near Kilbrittain, using Black-tailed Godwit (Limosa limosa), Curlew (Numenius arquata) and Teal (Anas crecca) as focal species. Differences in how species responded to disturbance and their foraging rates were also monitored. Data was collected by behavioural observations of the birds at multiple stations within each site. Species abundances during the study, details of disturbance events, and scans of feeding rates of the focal species were all recorded. Anthropogenic disturbance occurred more frequently at the open Kilbrittain site than at the Douglas Estuary mudflats. Disturbance events at Kilbrittain led to a higher proportion of birds being disturbed and bird responses were more severe. Differences within species in foraging rates were primarily exhibited at the Kilbrittain site. Curlews were the species most significantly affected by disturbance events. The study highlighted their vulnerability to increasing levels of anthropogenic disturbance at important shorebird habitats. Identifying and protecting such habitats is a vital part of conservation and management of shorebird populations. (WC: 334)