Effects of human disturbance on a mixed-species seabird colony in Patagonia

Abstract

Knowledge ofspecies sensitivity to disturbance may aid in the evaluation of potential impacts of human activity on seabird colonies. During 1989 to 1991 we evaluated the response of 5 seabird species to human presence at the Punta León mixed-species colony, a site currently proposed as a tourist reserve. The response of all species varied throughout the season. The distance at which Imperial Cormorants (Phalacrocorax atriceps) started to respond to human approach decreased as the season advanced (100 to 6.6 m). Nest abandonment of peripheral nesters occurred during a11 approaches at less than 8 m and only near the section of the colony approached. Exposed eggs were preyed upon by Kelp Gulls (Larus dominicanus). During settlement, some Olivaceous Cormorant (Phalacrocorax olivaceus) abandoned their nests when approached to less than 25 m and, during incubation, alert behavior was observed at less than 20 m. Distance at which Kelp Gulls started to flush in response to human approach also decreased as the season advanced (> 100 to 6.7 m). During the approach to the Royal (Sterna maxima) and Cayenne Tem (S. eurygnatha) colony, both settling and incubating peripheral individuals started to react with low intensity at approximately 20-25 m. Nest abandonment of incubating terns resulted in egg predation by Kelp Gull in three of the four approaches. The distances presented are minimum estimates which could be used as references when deciding the optimal distances at which visitors should be kept away in order to minimize disturbance to the breeding birds.