In 2000 and 2001, the only known North American breeding colony of Manx Shearwater (Puffinus puffinus) on Middle Lawn Island, Newfoundland was visited. Breeding was first confirmed in 1977 and by 1981, a minimum of 13 pairs laid eggs. In 2000, a complete assessment of all burrows was undertaken, and only 2 eggs were found; a third female had an egg in her oviduct. Based on female call rates, capture of birds, and offshore observations, the numbers of non-breeding shearwaters around Middle Lawn Island was comparable to the early 1980s, in the low 100s. The growth of a nearby large gull colony, changing marine ecosystems, and a short breeding season in the northwest Atlantic are possible explanations for why this colony has not become better established. Similar conditions could also be keeping the small Northern Fulmar (Fulmaris glacialis) and Common Black-headed Gull (Larus ridibundus) breeding populations in Atlantic Canada from expanding.