Does garbage in diet improve Glaucous Gull reproductive output?

Condor
By:  and 

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Abstract

Anthropogenic subsidies are used by a variety of predators in areas developed for human use or residence. If subsidies promote population growth, these predators can have a negative effect on local prey species. The Glaucous Gull (Larus hyperboreus) is an abundant predator in northern Alaska that is believed to benefit from garbage as a supplemental food source, but this supposition has never been tested. In summer 2008 and 2009, we recorded the Glaucous Gull's diet and reproduction at 10 breeding colonies in northern Alaska. Colonies were in industrial, residential, and undeveloped areas and ranged from 5 to 75 km from the nearest landfill. By colony, garbage occurred in zero to 85% of pellets and food remains produced during the chick-rearing period, and the average number of chicks fledged per pair ranged from zero to 2.9. Random-forest analysis indicated that percent occurrence of garbage in the diet was the second most important factor (after number of eggs per pair) explaining variance in fledging rate. There was a significant positive correlation between percent occurrence of garbage in the diet and fledging rate in each year. If this correlation reflects a causal relationship, it suggests that human development that increases gulls' access to garbage could result in increased local gull populations. Such an increase could affect the gulls' natural prey species, including at least 14 species of shorebirds and waterfowl of conservation concern.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Does garbage in diet improve Glaucous Gull reproductive output?
Series title Condor
DOI 10.1525/cond.2010.100020
Volume 112
Issue 3
Year Published 2010
Language English
Publisher Bioone
Contributing office(s) Coop Res Unit Leetown
Description 9 p.
First page 530
Last page 538
Online Only (Y/N) N
Additional Online Files (Y/N) N
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