Effects of motorboats and personal watercraft on flight behavior over a colony of Common Terns

I examined the flight behavior of Common Terns (Sterna hirundo) over a nesting colony in Barnegat Bay, New Jersey in 1997. I used the number of birds flying over the colony to test the hypothesis that there were no differences in flight behavior as a function of presence and type of craft (motor boat, personal watercraft). For the overall model, 66% of the variation in the number of terns flying over the colony was explained by breeding period, type of craft, speed, route (established channel or elsewhere), the interaction of route and speed, and time of day. However, for the early stage of the reproductive cycle, type of craft, speed, and route explained 95% of the variation. Boats that raced elicited the strongest response, as did boats that were outside of the established channel. Boats traveling closer to the nesting colonies elicited stronger responses than those that remained in the channel. Personal watercrafts elicited stronger responses than meter boats. These data suggest that personal watercraft should be managed to reduce disturbance to colonial-nesting species, by eliminating them within 100 m of nesting colonies and restricting speed near such colonies.