OVERWINTERING GULLS AT THE CHARLOTTETOWN SANITARY LANDFILL

by Geoff Hogan and Sue Stephenson

The use of garbage dumps and sanitary landfill sites by gulls is a common occurrance in North America and elsewhere. Fresh garbage deposited daily provides a regular and depend— able food source for these opportunistic birds. The impact that this food source has on gull populations is believed to be a contributing factor to the increase recorded in many areas, particularly of the Herring Gull.

Between January 15 and 24, 1982 several trips were made to the Charlottetown Sanitary Great Black-backed Gull Landfill in East Royalty to observe the species of gulls, their relative numbers and how they made use of the site. Herring and Great Black-backed Gulls were the most numerous species on each visit. The actual numbers were difficult to determine due to the constant activity; however estimates were generally 400-500 Herring Gulls and one hundred plus Great Black- backed Gulls. Adults and immatures of both species were present. On each visit one or two Glaucous Gulls were seen and, on one occasion, a single Iceland Gull was observed. Interestingly, Iceland Gulls were probably the most common gull observed within Charlottetown during the same period. Other birds regularly seen at the site included Common Crow, Northern Raven, Starling and House Sparrow.

The gulls spent their time between feeding on the garbage heaps and resting on nearby loafing areas. These activities were dependent upon the time of day and the amount of dumping going on, Activity ranged from the frenzied feeding behaviour during the morning hours, when gulls literally swarmed over the site, to the more relaxed periods during late afternoon when most birds rested nearby with only occasional forays to the garbage piles. At the approach of dusk the gulls left the dump, flew approximately 2 km south, where they gathered in large flocks on the ice of the Hillsborough River. As was typical of behaviour recorded at the loafing areas of the dump, Great Black-backed Gulls again chose the more exposed positions of the flock while Herring Gulls settled closer to the center.

While feeding on garbage, interactions between the gulls were frequent but there was no apparent dominance of one species over the other. Particularly aggressive individuals of either species were generally the victors in any dis— putes. Most interactions on the loafing area were between ravens and gulls. While the gulls sat quietly, individual ravens wandered among them, occasionally grabbing hold of a gull by a wing or tail. The sur- prised gull reacted with protest and threats, whereupon it was released and quickly settled d0wn. The raven '6;§§LEF then moved along to annoy another gull. Whether this iS§$§EEf"' behaviour on the part of the ravens was to obtain food

by causing gulls to regurgitate, or whatever, it was very amusing to watch. The consequences however may - be far more serious as implicated by the article by Daryl Guignion appearing elsewhere in this issue. Herring and Great Black—backed Gulls are adaptable birds, quick to take advantage of food sources made Herring Gull available by man. Both species frequent the vicinity

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