Volume 46, No. 2

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Reproductive ecology of urban-nesting Glaucous-Winged Gulls Larus glaucescens in Vancouver, BC, Canada


1Department of Statistics, University of British Columbia, 2207 Main Mall, Vancouver, BC V6T 1Z4, Canada
2Department of Educational and Counselling Psychology, and Special Education, University of British Columbia, 2125 Main Mall, Vancouver, BC V6T 1Z4, Canada


KROC, E. 2018. Reproductive ecology of urban-nesting Glaucous-Winged Gulls Larus glaucescens in Vancouver, BC, Canada. Marine Ornithology 46: 155 - 164

Received 01 November 2017, accepted 10 July 2018

Date Published: 2018/10/15
Date Online: 2018/8/30
Key words: Glaucous-winged Gull, Larus glaucescens, reproductive success, urban nesting, rooftop nesting, urban ecology, Vancouver


The present study investigated the reproductive success and breeding ecology of 102 Glaucous-winged Gull Larus glaucescens pairs nesting in downtown Vancouver, British Columbia during the summer of 2015. These urban breeders enjoyed a remarkably high level of post-hatch fledging success (≥ 85%) compared to previous records for non-urban subpopulations in the region (≈ 70%). A relatively small average initial clutch size of 2.43 eggs was observed, which aligns with a historical analysis of the literature and corroborates the inference that clutch size has declined substantially in the region over the past century. I argue that the high level of post-hatch fledging success is likely attributable to a tendency of urban Glaucous-winged Gulls to establish isolated nesting territories, often on the rooftops of individual buildings, which leads to low intra- and interspecific predation. Given that offspring commonly return to their natal sites to breed later in life, the evolutionary impact of this reproductive differential could be significant for the ecological future of Glaucous-winged Gulls in the region.


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