The effect of human disturbance on the local distribution of American oystercatchers breeding on barrier island beaches


19 – 26

1 April 10

Thomas Virzi

Thomas Virzi
Department of Ecology, Evolution, and Natural Resources, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901, USA.


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On the barrier beaches of New Jersey, USA, there is a high intensity of recreational activity that coincides with the breeding season for many beach-nesting birds, including the American Oystercatcher. Persistent human disturbance on or near breeding grounds could affect settlement and territory establishment of birds, causing them to abandon optimal habitat and settle in sub-optimal habitat. Explaining the distributional variation in response to human disturbance pressure is difficult; however, there are many recently developed species distribution modeling techniques that perform well for such analyses. I used classification and regression tree models to identify the most important variables explaining the distribution of American Oystercatchers in response to recreational activity in a highly disturbed coastal ecosystem, and compared the models with other more complex techniques. The classification and regression tree models performed well, and were the easiest models to implement and interpret making them an ideal choice for such analyses. My results indicated that human disturbance affects the local distributional patterns of American Oystercatchers on New Jersey barrier beaches. Probability of oystercatcher presence was lower on highly disturbed beaches and in areas that were in close proximity to access points. Further, there was lower probability of presence on beaches that permit driving during the month of May, which is the peak nest-initiation period for oystercatchers in the region. Probability of American Oystercatcher presence and abundance were greatest in highly suitable barrier beach habitat that had a low level of human disturbance. Therefore, I suggest that restrictions be placed on beach access and driving during the key breeding season on beaches that are predicted to be highly suitable for oystercatcher nesting.