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Location Canada, Ontario
Central coordinates 79o 19.48' West  43o 38.51' North
IBA criteria A4i, A4iii
Area 700 ha
Year of IBA assessment 2008

Bird Studies Canada/Nature Canada

Site description The Leslie Street Spit extends from the Toronto shoreline about 5 km southwest into Lake Ontario. It is located immediately to the east of the Toronto Islands and Harbour. It is a human-made feature that includes both Tommy Thompson Park and the Endikement Area. Tommy Thompson Park consists of a main road and four peninsulas that were constructed from dredge spoil between 1972 and 1975. Construction of the Endikement Area began in 1980 and is continuing. The three cells, which are closed to the public, store contaminated dredge from the Toronto Inner Harbour. Much of Tommy Thompson is now covered with dense thickets of cottonwoods and willows that support an impressive number of Black-crowned Night Heron nests.

Key Biodiversity At least two species are regularly present on Leslie Street Spit in significant numbers: Ring-billed Gulls and Black-crowned Night Herons. The long term Ring-billed Gull breeding population on the spit averages about 55,000 pairs. This represents about 6.2% of the world?s estimated breeding population, and as much as 9% of Canada?s estimated breeding population. A peak of 75,564 pairs was recorded in 1984, which is 8.4% of the global population.

Nationally significant numbers of Black-crowned Night-Herons are also present with as much as 30% (1,195 pairs) of the estimated Canadian breeding population being recorded in 1996. The long term average from 1983 to 1997 is 612 pairs, or 15% of the national population. The population increase in the late 1980s may have been the result of colonization from nearby Muggs Island. A gull eradication program resulted in a substantial reduction in the gull colony on Muggs. It has been suggested that the lack of gull eggs and chicks as food for the night-herons, and the availability of good nesting trees and large numbers of gull eggs and chicks at Leslie Street Spit, prompted the shift. Common Terns were formerly present in significant numbers, but their populations have declined considerably in recent years (from a maximum of 1,694 pairs in 1982 to a minimum of 108 pairs in 1989). Double-crested Cormorants have recently colonized the site, starting in 1990 at 10 nests, and increasing to an average of 1,204 pairs from 1994 to 1998, including a peak of 1,727 nests in 1997.

In addition to colonial birds, large concentrations of migrating songbirds have occurred on Leslie Street Spit, such as 370 American Pipits in October, 1994. Other records of note include a flock of 200 Whimbrel during the spring of 1994, and a concentration of 34 Long-eared Owls during the winter of 1997.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Ring-billed Gull Larus delawarensis breeding  1986  55,000 breeding pairs  A4i  Least Concern 
A4iii Species group - waterbirds breeding  1984  50,000-99,999 breeding pairs  unknown  A4iii   


IUCN habitat Habitat detail Extent (% of site)
Forest Temperate deciduous woods  5%
Shrubland Scrub  8%
Wetlands (inland) Freshwater lakes and pools; Freshwater marshes/swamps; Intertidal mud, sand or salt flats  32%
Coastline Rocky flats & barrens  16%
Artificial - terrestrial Urban parks and gardens  19%
Other   20%

Land use

Land-use Extent (% of site)
nature conservation and research major
tourism/recreation major
urban/industrial/transport major

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Leslie Street Spit. Downloaded from on 23/10/2016

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