Over 50 species live in the sanctuary and 30 of these species are breeders. Roughly 320,000 thick-billed Murres and 50,000 Kittiwakes share Bylot Island's cliffs. These circumpolar and colonial species are pelagic seabirds outside the breeding season. After spending the year at sea, they return to their nesting cliff every spring. Murres, which are related to Puffins and the extinct Great Auk, can dive down over 100 meters in search of prey.
Kittiwakes are small gulls which search the water's surface for small surface organisms.
The population of Murres has increased over the last decades. Up to one million Murres alone once summered at Cape Hay. However, many have died in fishing nets while feeding in the winter. Approximately 75,000 Greater Snow Geese can be seen in Bylot Island's South-western lowlands at the end of summer. The population has increased from an estimated 3,000 in 1900 to 300,00 in 1998.