Response of waterbirds to experimental disturbances

Responses of waterbirds to experimental disturbances were studied from April 1984 to August 1985 at Russell Lakes State Wildlife Area in the San Luis Valley, Colorado. Black-crowned night-herons (Nycticorax nycticorax), snowy egrets (Egretta thula) and white-faced ibis (Plegadis chihi) were approached directly by a person on foot or in a motor vehicle. Mean (±SD) flushing distances for these species were 153±66, 93±43, and 95±48 m when approached on foot and 47±26, 57±27, and 54±27 m when approached in a motor vehicle. Reactions of American coots (Fulica americana), redheads (Aythya americana), ruddy ducks (O ura jamaicensis), mallards (Anas platyrhynchos), gadwalls (A. strepera) and American avocets (Recurviroslra americana) to disturbance were also quantified. Intensity of response was independent of agent of disturbances (i.e., person on foot or in vehicle) for all species. Disturbance reduced species diversity and abundance for up to one hour. American coots and avocets were only minimally impacted by the disturbance agents used.