Pacific Southwest

Title: Effects of human disturbance on the breeding success of gulls

Author: Robert, Henry C.; Ralph, C. John

Date: 1975

Source: The Condor 77(4):495-499

Description: A number of factors have been suggested as affecting reproductive success in gulls. In this study we have attempted to isolate the effect of human disturbance on breeding success. We held other factors such as age of birds, terrain, and density of colony as constant as was practicable with a varied colony environment. There have been several previous discussions of the possible effect of human disturbance on the breeding success of birds. However, no study has documented this effect with controls. Reid (1968) found that in the Adélie Penguin (Pygoscelis adeliae) "banding and close observation during seven summers caused the breeding populations in six colonies to decrease by more than 90%." Nelson (1966), commenting on nests on the fringe of colonies, stated that their lower success rates did not take full account of artifacts introduced by human disturbance. Working with the Sooty Tern (Sterna fuscata), Ashmole (1963:324) said that "mortality caused by the pecking of chicks by adults was increased enormously by any human disturbance of the colony." Kadlec and Drury (1968: 657) provided some information on the effect of human disturbance, and compared islands visited occasionally with those being studied in detail. Although they acknowledged an effect, they considered it insignificant compared to environmental variables. Hunt (1972), in studying four small Herring Gull (Larus argentatus) colonies, found that two colonies, frequently disturbed by picnickers, had lower hatching success than two undisturbed colonies. He found no difference in the ability of parents to raise young. These latter two studies most systematically approach the problem, but each compares totally different colonies that are, of course, under a variety of environmental conditions.

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Citation

Robert, Henry C.; Ralph, C. John  1975.  Effects of human disturbance on the breeding success of gulls .   The Condor 77(4):495-499.