Threats to the marine environment are on the rise in the Bay of Fundy and the Gulf of Maine. Significant changes in marine food webs are already affecting the most important seabird breeding site in New Brunswick, Machias Seal Island. During the breeding season, this island is home to several seabird species, including regionally important colonies of Atlantic Puffins (Fratercula arctica) and Razorbills (Alca torda). These two auks coexist sympatrically during the breeding season, occupying similar dietary niches. Additionally, these birds are central place foragers, restricting their foraging ranges by the need to make several return trips (~10 per day) to feed their young or relieve their mate. In recent years, their food supply has deteriorated and there is concern for the future of auks in this region. Current knowledge of their at-sea distribution in the Bay of Fundy is especially fragmented, depending mainly on casual observations by passersby or the occasional survey. Until recently, GPS loggers providing fine scale data, were too large to deploy on any but the largest seabirds. Using a mix of GPS technology and direct observation of chick diet, I determined that puffins and razorbills avoid niche overlap by foraging in different places. Slight differences in diet and dive depth are likely consequences of foraging location. Despite detecting no differences in nest attendance, provisioning, and chick growth at the burrow-level, individual behavioural observations revealed that mates of individuals equipped with loggers provisioned significantly more than their tagged mate. These findings show that important tag effects can be overlooked with conventional methods.
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