Both human activities and environmental conditions influence foraging oystercatchers on urban beaches

In developed coastal areas, shorebirds utilising sandy beaches as their primary habitat are often disturbed by human activities. Shorebird responses to human activities can have fitness consequences, through changes in their behaviour. In this study, we investigated whether human activities (number of people, presence of dogs) and environmental factors (air temperatures, wind speeds) influenced the abundance and the percentage of foraging birds for two urban shorebird species; Haematopus longirostris (Pied Oystercatcher) and Haematopus fuliginosus (Sooty Oystercatcher). We found that the number of oystercatchers (abundance) was lower when many people and dogs were present. However, a higher percentage of oystercatchers were observed foraging when people were present in high numbers and when dogs were present, a pattern that seems to be driven by Sooty Oystercatchers rather than Pied Oystercatchers. We also found that oystercatcher abundance and the percentage of foraging birds showed a negative relationship with air temperature and a positive relationship with wind speed. We discuss these results in the context of our study sites and the implications they may have for oystercatcher foraging habits, reinforcing the idea that multiple factors need to be investigated when assessing the potential impacts of human activities on shorebirds.