Relatively little is known about the feeding ecology of grizzly bears (Ursus arctos) in Wapusk National Park. Other ursids, polar bears (Ursus maritimus), are well known predators of waterfowl nests in the area, and grizzly bears could feasibly make use of such resources. However, since the arrival of polar bears on land in the spring is largely dependent on date of sea-ice breakup, the timing of predation by each bear species may differ. We investigated the timing of bear predation in common eider (Somateria mollissima sedentaria) and lesser snow goose (Anser caerulescens caerulescens) colonies from 2012 to 2018 using nest cameras. We observed grizzlies consuming eggs of both species in all years except 2013 and confirmed that at least two individual grizzlies occupied the park in 2016. In the 3 years when both grizzly and polar bears were detected, grizzlies were observed earlier in the year than polar bears and had greater overlap with an estimated availability index of incubating waterfowl. We hypothesize that grizzly bears could have earlier access to waterfowl eggs in the park, potentially reducing availability of these terrestrial foods to polar bears.

中文翻译：

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灰熊 (Ursus arctos) 和北极熊 (Ursus maritimus) 作为 Wapusk 国家公园水禽巢穴捕食者的物候比较

关于瓦普斯克国家公园灰熊 (Ursus arctos) 的觅食生态知之甚少。其他熊类动物，北极熊 (Ursus maritimus)，是该地区众所周知的水禽巢穴捕食者，灰熊可能会利用这些资源。然而，由于北极熊在春季登陆陆地在很大程度上取决于海冰破裂的日期，因此每种熊的捕食时间可能会有所不同。我们使用巢穴相机调查了 2012 年至 2018 年间普通绒毛（Somateria mollissima sedentaria）和小雪雁（Anser caerulescens caerulescens）群落中熊捕食的时间。我们观察到灰熊在除 2013 年之外的所有年份都食用这两种物种的蛋，并确认至少有两只单独的灰熊在 2016 年占领了公园。在同时发现灰熊和北极熊的 3 年中，灰熊比北极熊更早被观察到，并且与估计的孵化水禽可用指数重叠更大。我们假设灰熊可以更早地获得公园里的水禽蛋，这可能会减少北极熊对这些陆生食物的供应。