Gulls (Larus spp.) are described as generalist, opportunistic feeders that show great flexibility in habitat use. Despite an apparent advantage in changing landscapes, many Larus populations have declined in eastern North America since the 1990s. The main hypothesis explaining gull declines at a broad scale is a decrease in total food availability, especially anthropogenically derived fisheries discards and human refuse as industries and cities have improved their management practices. However, it is difficult to quantify the total proportion of gull diet subsidized by humans to test this hypothesis because many common prey items can be traced to both anthropogenic and nonanthropogenic sources. Our aim was to estimate the proportion of diet derived from anthropogenic food sources for Herring Gull (L. argentatus) during the breeding season at the two largest colonies in the Bay of Fundy, Canada, which are located 36 km apart. GPS loggers were deployed to quantify spatiotemporal movement patterns, and whole blood and feather samples were collected for δ13C and δ15N stable-isotope analysis to estimate diet composition during the incubation and chick-rearing stages of the breeding season. Results indicate that there is spatial segregation in the foraging areas used by gulls from the two colonies. All gulls relied on a variety of anthropogenic food sources, with some individuals selecting heavily on fisheries (i.e., active town wharfs, fish packaging plants, aquaculture pens) and mink (Neovison vison) fur farms. Landfills were not a significant source of food during the breeding season. Our study provides valuable information about the relative reliance of gulls on anthropogenic food subsidies, providing insight into how changing industry practices may affect patterns in nesting and foraging by gulls in the region.

中文翻译：

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估计加拿大芬迪湾的鲱鱼鸥（Larus argentatus）对人为资源的相对利用

海鸥（Larus spp。）被描述为多面的机会饲养者，在栖息地使用中显示出极大的灵活性。尽管在改变景观方面具有明显的优势，但自1990年代以来，北美东部的许多Larus人口都在下降。解释大范围海鸥数量下降的主要假设是总的食物供应量减少，尤其是随着工业和城市管理方法的改进，人为来源的渔业丢弃物和人类垃圾的减少。但是，很难量化人类为检验这一假设而补贴的鸥食的总比例，因为许多常见的猎物都可以追溯到人为和非人为来源。我们的目的是估计鲱鱼鸥（L. 在繁殖季节，位于加拿大芬迪湾的两个最大殖民地，相距36公里。部署了GPS记录器以量化时空运动模式，并收集全血和羽毛样本用于δ13C和δ15N稳定同位素分析，以评估繁殖季节的孵化和养鸡阶段的饮食组成。结果表明，来自两个殖民地的海鸥在觅食区存在空间隔离。所有海鸥都依赖多种人为食物来源，有些人大量选择渔业（即活跃的城镇码头，鱼品包装厂，水产养殖场）和水貂（Neovison vison）皮草场。在繁殖季节，垃圾填埋场不是重要的食物来源。