Sable Island is located in the Atlantic Ocean about 150 km off the eastern shore of Nova Scotia. The 41 km sandbar island is located on the continental shelf, and is based on a (former) moraine. It is partly eroded each winter, with the sand being re-deposited each summer. There is a constant shifting of the partially vegetated sand dunes and offshore bars - the patterns depending on direction and force of major storms. But on average, there has been little change over the last 200 years. The climate is maritime: windy and mild, with snow seldom lying on the ground for more than a few days. The tide range is about 2 m. About 16,000 Grey Seals pup on the island each January, with about 500 Harbour Seals pupping each June.
Sable Island supports practically the entire population of the nationally vulnerable Ispwich Savannah Sparrow (ssp. princeps) - a few errant females have nested with male Savannah Sparrows on mainland beaches in Halifax County, Nova Scotia. During an extensive study during the late 1960s and 1970s, the average population recorded was about 2,300 adults in the late spring and about 10,000 in the late summer.
Sable Island also supports large numbers of nesting colonial waterbirds, some in globally significant numbers, such as Herring Gulls (2,000 pairs in 1970, representing over 1% of the North American population), Great Black-backed Gulls (600 pairs in 1998, representing over 1% of the North American population), and Common Terns (2,570 pairs in 1995, representing about 5% of the North American population). The nationally threatened Roseate Tern also nests here, with 10 pairs of them estimated among the larger colonies of Common and Arctic Terns in 1985. In August of that year, a rocket net sample of a flock of about 1,000 terns yielded four Roseate Terns out of the 70 that were caught. If this was a representative sample, as many as 60 adult Roseate Terns may have been present. During the mid 1990s, estimated numbers of nesting Roseates have ranged from a low of one pair in 1997 and 1998, to a high of four pairs in 1993.
The numbers of terns nesting on the island was formerly much larger, being estimated at close to a million birds at the turn of the century. Tern numbers have declined on the island, likely as a result of the increasing numbers of nesting Herring and Great Black-backed Gulls.
BirdLife International (2019) Important Bird Areas factsheet: Sable Island, Nova Scotia. Downloaded from http://www.birdlife.org on 05/12/2019.