IMPORTANCE OF LANDFILLS TO NESTING HERRING-GULLS

We determined the importance of three landfills to a population of nes ting Herring Gulls (Larus argentatus, 3,250 pairs) on Lake Erie, Ohio, from May-July 1992. Fish was the dominant food of adults and chicks t hroughout the study. Occurrence of garbage in the diet of adults and c hicks remained low through chick-rearing then increased after hedging. Presence of telemetered adults at their nest sites decreased from inc ubation through post-hedging, in contrast to their increased presence at landfills during the same periods. Overall, females visited landfil ls more frequently and stayed longer than males; however, use of landf ills by both sexes was minimal (<4% of total time) during all periods. Overall, gulls spent 43% and 4% of their time daily at the nest site and landfills, respectively. We estimate greater than or equal to 80% of the time remaining was spent on Lake Erie, presumably to forage. Th e estimated daily mean number of adult Herring Gulls at the landfills increased from incubation (143) to chick-rearing (723) to post-fledgin g (1,912). We estimate that 5-7%, 12-19%, and 35-55% of the adult nest ing population was present at landfills at least once during incubatio n, chick-rearing, and post-hedging, respectively. The population turno ver rate of adult Herring Gulls at one landfill decreased 50% from inc ubation and chick-rearing to post-hedging. Significantly more gulls at the landfills were observed on areas other than exposed refuse and we re not actively foraging, suggesting that landfills are important to H erring Gulls for other reasons such as leafing or social interaction. We conclude-that landfills are unimportant to nesting Herring Gulls wh en alternate, higher quality food (e.g., fish) is available. The incre ased use of landfills by Herring Gulls during post-hedging, however, s uggests that gull activity at landfills located near airports could dr amatically affect aircraft safety during this time of year.