Protecting Waterbirds From Watercraft

"Wildlife viewing…may cause waterbirds to abandon sites that managers are attempting to protect," say James Rodgers and Stephen Schwikert of the Florida Fish and Wildlife Conservation Commission in Gainesville in the February issue of Conservation Biology.

In 1999, Florida had more than 140,000 registered jetskis and other personal watercraft (PWC), and there are an estimated 1.3 million in the U.S. PWCs can mean trouble for waterbirds because they can navigate the shallow, secluded waterways where birds like to eat and rest.

To help protect waterbirds from PWCs and motorboats, Rodgers and Schwikert determined flush distances for 23 species at 11 sites along the east and west coasts of Florida.

Despite the PWC's reputation for noise and wildlife disturbance, Rodgers and Schwikert found that flush distances were greater for motorboats most (80%) of the time. For PWCs, the average flush distance ranged from about 65 feet for least terns to 160 feet for osprey; for a 14-foot motorboat, the average flush distance ranged from about 75 feet for Forster's terns to 190 feet for osprey. In general, larger birds had greater flush distances, which makes sense because they need more time to take flight due to their slower take-offs and flight speeds.

Based on their data, Rodgers and Schwikert conclude that a single buffer zone can protect waterbirds from both PWCs and motorboats. Specifically, they recommend buffer zones of about 330 feet for plovers and sandpipers, 460 feet for terns and gulls, 490 feet for osprey and 590 feet for wading birds. However, the researchers caution that managers should customize the buffer distances for individual sites and waterbirds because some populations are more sensitive than others. For instance, great white herons in the Florida Keys had a 25% greater flush distance than great blue herons along the mainland.