Marine Ornithology

The feeding ecology and behavior of breeding Iceland Gulls Larus glaucoides kumlieni and, to a lesser extent, American Herring Gulls Larus smithsonianus and Glaucous Gulls Larus hyperboreus, were studied at a large Iceland Gull colony located near Kinngait, Baffin Island, Canada. Iceland Gulls collected food close to the colony, mainly at ebbing and low tides, on or very close to the shoreline, and in adjacent nearshore waters. The most common feeding technique was picking on the water surface while swimming. Additional techniques included plunging to capture food items at greater depths and kleptoparasitism. Known food items included marine invertebrates and small fish. American Herring and Glaucous gulls nested in the study area in substantially lower numbers than Iceland Gulls but used similar feeding habitats and techniques and collected similar food items. The specific feeding techniques used by all three species were typical of many large Larus gulls. Sufficient food availability at the time of the study may explain some of the observed similarities in feeding habitat use and behavior. An important component of broad niche separation for Iceland Gulls in areas of sympatry may be sea-cliff nesting and concentrated use of coastal marine habitats for feeding, including shorelines and nearshore areas. In addition, other studies have shown that American Herring and Glaucous gulls use more inland and terrestrial habitats, use more diverse foods, and employ different feeding behaviors, including more predation and scavenging. Additional studies in selected areas are needed to fully address the questions raised in this study.