The Bird Islands are located in northeastern Cape Breton Island, approximately 4 km off Cape Dauphin. They consist of two long, narrow islands that are oriented in a northeast/southwest straight line. Hertford Island, located closest to shore, is approximately 1.1 km long and about 120 m wide. Ciboux Island, which is located directly northeast of Hertford Island, is slightly larger, being approximately 1.6 km long and about 120 m wide. Steep twenty-metre high cliffs, with numerous holes and ledges, ring the perimeters of both islands. The vegetation consists of stunted shrubs along with areas of grass and other forbs. These grassy tops were formerly grazed by herds of sheep. Numerous reefs and rock clusters are located between the two islands.
The Bird Islands support the largest colony of Great Cormorants in North America. A three-year average, using the 3 most recent years that the area was surveyed, was 565 nesting pairs. These do not reflect exact numbers, since the individual birds move frequently when surveys are being conducted. If approximately accurate, this number represents as much as 9% of the western Atlantic (North American) population.
Although Great Cormorants often breed inland in Europe and Asia, they are strictly coastal breeders in North America. Cormorants prefer nest sites that are within commuting range of adequate food resources and safe from terrestrial predators. As a result, isolated islands, and steep rocky cliffs that are within commuting range of adequate food resources, are favoured as nesting sites.
In addition to Great Cormorants, several other seabirds nest on the cliffs the Bird Islands are the largest concentration of Black-legged Kittiwakes, Razorbills and Atlantic Puffins within Nova Scotia. Numbers of the first two species have increased since the 1980s, with an average of 960 kittiwake, 150 Razorbill, and 75 puffin nesting pairs over the last five surveyed years (between 1990-1997). A few hundred nesting pairs of Double-crested Cormorants, over 300 Black Guillemots, and Leachs Storm-Petrels also breed on here.
Other birds that have been observed on the islands include: Spotted Sandpipers, yellowlegs, Cliff Swallows, Herring Gulls, Greater Black-backed Gulls and Starlings.
BirdLife International (2020) Important Bird Areas factsheet: Bird Islands. Downloaded from http://www.birdlife.org on 29/11/2020.