Use of anthropogenic foods by glaucous gulls (Larus hyperboreus) in northern Alaska

Abstract

"Glaucous Gulls are abundant predators in northern Alaska and prey upon several bird species of conservation concern. To assess the benefit gulls may receive from scavenging garbage, I studied diet and reproduction at eight to ten breeding colonies in northern Alaska in 2008-2009. Garbage occurrence in diet was positively correlated with fledging rate; thus any development that increased available garbage could potentially subsidize gull populations through enhanced reproductive success. Garbage could also increase gull populations by enhancing subadult survival. Subadult gulls around the city of Barrow consumed much more garbage than breeding adults, which apparently switch to a mostly natural diet. If garbage enhances subadult survival, more gulls may survive to adulthood, which could impact prey species. When Barrow switched to incinerating garbage instead of disposing it in a landfill, garbage in subadult gull diet decreased. Using stable isotope analysis of gull chick feathers, I found that the diet samples (pellets and food remains) I used in these analyses overestimated gull use of birds and underestimated use of fishes, but usually accurately portrayed relative importance of garbage. Biases in these samples should be considered when assessing the potential impact of gulls on their prey"--Leaf iii