These reefs support globally significant numbers of breeding colonial waterbirds, especially American White Pelican, Double-crested Cormorant and Caspian Tern.
The Spruce Island Reefs support globally significant numbers of Caspian Terns, and a large mixed colonial waterbird colony. Approximately 3,000 Caspian Terns nested on the Spruce Island Reefs in 1999. This represents over 3% of this species North American population, and may have been the largest Caspian Tern colony in Canada.
In 1999, there were 1,467 American White Pelicans nesting on Dory’s Reef, over 1% of the global breeding population of this species. Large numbers of Common Terns also nest at Dorys Reef; a 1999 survey found 641 nests.
North Long Island (north end) supported 817 American White Pelican nests and 4,540 Double-crested Cormorant nests in 1999. North Long Island (south end) also supported significant concentrations of breeding cormorants and pelicans in 1999. There were 8,032 Double-crested cormorant nests, which is over 1% of this species global population. There were also 1,925 American White Pelican nests, which is more than 1% of the estimated global population of this species.
A survey in 2012 counted a total of 2,373 American White Pelican nests between the six reefs, representing over 2% of the global breeding population of this species. There were also 8,468 Double-crested Cormorants adults, 387 Caspian Tern nests, 325 Common Tern nests, 2,728 Ring-billed Gull adults and 189 Herring Gull adults. Small numbers of California Gull, Bald Eagle, American Widgeon, Canvasback, Redhead, Common Merganser and Red-breasted Merganser have also been recorded here during breeding surveys.