Responses of Shorebirds to Disturbance at Roosting Sites

The sources and the frequency of disturbances and the responses of shorebirds to disturbanceswere studied at four roosting sites on Ganghwa Island and Yeongjong Island. The mean frequency of disturbanceto roosting shorebirds was 2.7 per hour. Human activities contributed to the disturbance in 65% of all cases.Disturbance frequencies in saltpans were higher than those in the upper tidal zone, fishponds and salt marshes.Response patterns of shorebirds to disturbances were associated with the source of the disturbance. Disturbancecaused shorebirds to change their behavior and to reduce roosting time at their roosting sites. Four patternsof responses by roosting shorebirds to disturbance were found, including: (1) leaving the roosts, (2) changingtheir location within the site, (3) leaving and returning, and (4) remaining in place. In the latter three responsepatterns, the birds tended to remain in their initial roosting sites, in contrast with the leaving pattern, whichinvolved departing from the roosting area. Factors affecting these response patterns were time from high tideand time of day. When the time from high tide was greater, and the time of day was later, more birds stayedat the roost. The absence of sufficient alternative roosts in the study areas forced the birds to choose betweentolerating the current disturbance, or moving to distant roosts.