Stable Mercury Trends Support a Long-Term Diet Shift Away from Marine Foraging in Salish Sea Glaucous-Winged Gulls over the Last Century

Choy, Emily S.; Blight, Louise K.; Elliott, John E.; Hobson, Keith A.; Zanuttig, Michelle; Elliott, Kyle H.

doi:10.1021/acs.est.1c03760

Cited by 3 publications

(1 citation statement)

References 54 publications

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“…However, legacy persistent organochlorine pollutants such as DDT did not decline in coastal environments until the 1980s (Elliott and Elliott 2013), meaning the region's gulls studied historically, and serving as our points of comparison, were also exposed to endocrine-disrupting contaminants. They have likely also been exposed to increasing amounts of methyl mercury over time, but this exposure has been ameliorated to some degree by shifts to lower trophic-level diets on average (Choy et al 2022).…”

Section: Discussionmentioning

confidence: 99%

A comparison of historical and contemporary reproductive traits in a declining population of Glaucous-winged Gulls (Larus glaucescens)

Blight¹,

O’Shea²,

McClelland³

2022

ACE

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Understanding how organisms manage life history trade-offs under variable environmental conditions is an aim that is central to ecology. Comparing modern reproductive data with those from historical studies can increase understanding of the range of historical conditions that have acted on a given species over time. We use recent (2008-2010) and historical (1960s-1980s) reproductive data from a single study colony, Mandarte Island, Canada, to help understand the recent population declines experienced by the Glaucous-winged Gull (Larus glaucescens) in North America's Salish Sea, a highly urbanized area. Because this long-lived species has also undergone regional long-term declines in reproductive investment via decreasing egg and clutch size, we assessed whether modern reproductive outcomes were similarly affected. Although our statistical power was hampered by small sample sizes, it appears that hatching success declined over time, from 0.83 (1960s) and 0.76 (1970s-1980s) to 0.60 (2008-2010). An apparent decline in nesting success, from 0.63 (1962) to 0.52 (this study), was not statistically significant. Recent clutch sizes showed intra-seasonal declines, a pattern unchanged from historical trends. In contrast, egg mass historically was constant within a given nesting season, but recent eggmass data show intra-seasonal declines. We conclude that most gulls currently breeding on Mandarte Island cannot attain historical levels of reproductive success -perhaps because of declining environmental quality in the form of reduced availability of high-quality fish prey -although some high-quality pairs in this population are still able to maximize reproductive output. Our study highlights the importance of long-term study systems for identifying consequences of large-scale ecosystem changes; however, methodological clarity is essential to ensure data comparability through time. Ultimately, further study is needed to identify the drivers of reproductive changes in this population, something that could be used to inform future management decisions. Comparaison de paramètres de reproduction historiques et contemporains d'une population de Goélands à ailes grises en diminution (Larus glaucescens)RÉSUMÉ. La compréhension des compromis que doivent faire les organismes durant leur cycle de vie en fonction des conditions environnementales variables est un objectif central de l'écologie. La comparaison de données modernes sur la reproduction avec celles d'études historiques peut permettre de mieux comprendre la gamme de conditions historiques qui ont agi sur une espèce donnée au fil du temps. Nous avons utilisé des données de reproduction récentes (2008-2010) et historiques (années 1960-1980) provenant d'une seule colonie, l'île Mandarte, au Canada, pour tenter de comprendre les récentes baisses de population chez le Goéland à ailes grises (Larus glaucescens) dans la mer des Salish, en Amérique du Nord, une zone fortement urbanisée. Étant donné que cette espèce longévive a également subi des diminutions régionales de longues dat...

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Section: Discussionmentioning

confidence: 99%