IBA Leslie Street Spit
Toronto, Ontario
Site Summary
ON038 Latitude
43.633° N
79.329° W
?? m
10.84 km²
deciduous woods (temperate), scrub/shrub, freshwater lake, freshwater marsh, mud or sand flats (freshwater), urban parks/gardens, rocky flats & barrens, other
Land Use:
Nature conservation and research, Tourism/recreation, Urban/industrial/transport
Potential or ongoing Threats:
Disturbance, Interactions with native species/disease, Industrial pollution, Introduced species, Other decline in habitat quality, Other environmental events, Recreation/tourism
IBA Criteria: Globally Significant: Congregatory Species, Colonial Waterbirds/Seabird Concentrations, Continentally Significant: Congregatory Species, Nationally Significant: Congregatory Species, Wading Bird Concentrations
Conservation status: Conservation Authority (owned by), IBA Conservation Plan written/being written
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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.
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.

IBA Criteria
SpeciesT | A | I Links Date Season Number G C N
Acadian Flycatcher 2016 - 2019 SP 1
Acadian Flycatcher 2009 SU 2
Black-crowned Night Heron 1990 - 2003 SU 1,224 - 2,390
Chimney Swift 2001 - 2020 FA 24 - 100
Chimney Swift 2007 - 2020 SP 24 - 300
Chimney Swift 2010 - 2020 SU 24 - 250
Double-crested Cormorant 2017 - 2020 FA 15,000 - 20,000
King Rail 2010 FA 1
Kirtland's Warbler 1991 SP 1
Little Gull 2018 FA 3
Little Gull 2019 - 2020 SP 2 - 3
Loggerhead Shrike 2016 SP 1
Prothonotary Warbler 2007 - 2010 SP 1
Red-breasted Merganser 2010 - 2019 FA 2,000 - 4,000
Red-necked Grebe 2014 - 2018 SP 430 - 700
Ring-billed Gull 2011 SP 100,000
Ring-billed Gull 1984 - 1986 SU 110,000 - 149,128
Rusty Blackbird 2005 - 2018 FA 25 - 90
Rusty Blackbird 2017 - 2020 SP 25 - 33
Yellow-breasted Chat 2017 FA 1
Yellow-breasted Chat 2011 - 2020 SP 1 - 2
Note: species shown in bold indicate that the maximum number exceeds at least one of the IBA thresholds (sub-regional, regional or global). The site may still not qualify for that level of IBA if the maximum number reflects an exceptional or historical occurrence.
Conservation Issues
The Leslie Street Spit is accessible to mammalian predators, and the colonies are subject to chronic disturbances by people and their dogs. Vegetation succession and predation by Ring-billed Gulls on eggs and young of other colonial species are also continuing problems. Numerous conservation measures have been taken, and others are in progress or have been proposed, including: vegetation control, control of Ring-billed Gull populations, reduction of human interference, creation of new nesting habitat, and control of mammalian predation on eggs and chicks.

The IBA Program is an international conservation initiative coordinated by BirdLife International. The Canadian co-partners for the IBA Program are Birds Canada and Nature Canada.
   © Birds Canada