Wading Bird Response to Recreational Boat Traffic: Does Flushing Translate into Avoidance?

Abstract

It generally is assumed that direct flushing responses to disturbance may affect overwintering bird fitness by altering site use. However, little is actually known about the relationship between the flushing response and resulting patterns of habitat use on a local scale. We examined the association between flushing and local site use among 6 wading bird species in tidal creeks on the Cape Romain National Wildlife Refuge, South Carolina, USA, which is frequently used for recreational activities. Experimental, cumulative boat intrusion caused approximately one-half of individuals of all species except snowy egrets (Egretta thula) to immediately abandon a tidal creek. However, species counts across the refuge tended to be driven primarily by Julian date, tidal stage, and creek width; only 2 species, yellow-crowned night heron (Nyctanassa violacea) and great egret (Ardea herodias), appeared to avoid high-traffic creeks. Overall, patterns of response varied among species, and there was no clear relationship between flushing and site use. Flush rates, thus, may not adequately reflect species sensitivity to human disturbance and should only be used as a management guide in conjunction with other indices such as spatial distribution.