Egg production in a coastal seabird, the glaucous-winged gull (Larus glaucescens), declines during the last century.
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TLDR
It is demonstrated that glaucous-winged gull investment in egg production has declined significantly over the past ∼50–100 y, with such changes potentially contributing to recent population declines and the incremental long-term impoverishment of a coastal marine ecosystem bordering one of North America's rapidly growing urban areas.Abstract:
Seabirds integrate information about oceanic ecosystems across time and space, and are considered sensitive indicators of marine conditions. To assess whether hypothesized long-term foodweb changes such as forage fish declines may be reflected in a consumer's life history traits over time, I used meta-regression to evaluate multi-decadal changes in aspects of egg production in the glaucous-winged gull (Larus glaucescens), a common coastal bird. Study data were derived from literature searches of published papers and unpublished historical accounts, museum egg collections, and modern field studies, with inclusion criteria based on data quality and geographic area of the original study. Combined historical and modern data showed that gull egg size declined at an average of 0.04 cc y−1 from 1902 (108 y), equivalent to a decline of 5% of mean egg volume, while clutch size decreased over 48 y from a mean of 2.82 eggs per clutch in 1962 to 2.25 in 2009. There was a negative relationship between lay date and mean clutch size in a given year, with smaller clutches occurring in years where egg laying commenced later. Lay date itself advanced over time, with commencement of laying presently (2008–2010) 7 d later than in previous studies (1959–1986). This study demonstrates that glaucous-winged gull investment in egg production has declined significantly over the past ∼50–100 y, with such changes potentially contributing to recent population declines. Though gulls are generalist feeders that should readily be able to buffer themselves against food web changes, they are likely nutritionally constrained during the early breeding period, when egg production requirements are ideally met by consumption of high-quality prey such as forage fish. This study's results suggest a possible decline in the availability of such prey, and the incremental long-term impoverishment of a coastal marine ecosystem bordering one of North America's rapidly growing urban areas.read more
Citations
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feathers collected in the Pacific Northwest of North America
TL;DR: The authors used stable isotope (δ(13)C, δ(15)N) analysis of feathers from glaucouswinged gulls (Larus glaucescens) in a heavily disturbed region of the northeast Pacific to ask whether diets of this generalist forager changed in response to shifts in food availability over 150 years, and whether any detected change might explain long-term trends in gull abundance.
Journal ArticleDOI
Changing gull diet in a changing world: A 150‐year stable isotope (δ13C, δ15N) record from feathers collected in the Pacific Northwest of North America
TL;DR: Stable isotope analysis of feathers from glaucous-winged gulls in a heavily disturbed region of the northeast Pacific suggests a long-term decrease in diet quality linked to declining fish abundance or other anthropogenic influences, and may help to explain regional population declines in this species and other piscivores.
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Egg cannibalism in a gull colony increases with sea surface temperature
James L. Hayward,Lynelle M. Weldon,Shandelle M. Henson,Libby C. Megna,Brianna G. Payne,Andre E. Moncrieff +5 more
TL;DR: Food-stressing surface feeders such as gulls, diminishing energy intake and lengthening foraging bouts, and increasing levels of cannibalism could lead to declining populations in the absence of compensatory adaptive modifications or range shifts are tested.
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A three‐generational study of In ovo exposure to PBDE‐99 in the zebra finch
TL;DR: It is suggested that egg levels as low as 10 ng/g BDE‐99 may affect reproduction in small passerines by reducing clutch size and no evidence of effects over the longer term and in successive generations is found.
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