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Location Canada, Yukon Territories
Central coordinates 134o 24.09' West  60o 33.05' North
IBA criteria A4i, A4iii
Area 5,000 ha
Altitude 1,000 m
Year of IBA assessment 2008

Bird Studies Canada/Nature Canada

Site description MClintock Bay and the Lewes River Marsh are located about 30 kilometres southeast of Whitehorse, in the Yukon Territory. The shallow MClintock Bay is at the north end of Marsh Lake; here the outflow of the Yukon River is adjacent to the inflowing MClintock River, which has a rich delta, mudflats and beds of submergent aquatic vegetation, including pondweeds. Three kilometres downstream along the Yukon River is the Lewes River Marsh, which consists of side channels, shallows, marshes and mudflats on both sides of the main channel.

Key Biodiversity This area is an important and high profile spring migration area for waterfowl; arguably southern Yukons most well known and most heavily used spring migration area. The outlets of certain lakes, such as this site, are the first open water available in the spring and are heavily used by birds wherever they coincide with shallow water and food. Globally significant numbers of Trumpeter Swans pass through in spring migration, with up to 1,500 birds (around 7.5% of the global population) being seen in one day. It is estimated that perhaps 6,000 birds (over a quarter of the global population) utilize the area in the spring. Their close relative, the Tundra Swan, can be seen in the area in even larger numbers, with peak one day counts approaching 2,000 birds (almost 2% of the western population) and estimated spring totals of over 12,000. Waterfowl are seen in globally significant numbers, with over 50,000 birds estimated using the site annually, most importantly in spring. Over 20 species of waterfowl stage or breed here - Northern Pintail, American Wigeon and American Green-winged Teal are some of the commonest species.

Shorebirds use the mudflats primarily during spring migration. A count of 1,800 Pectoral Sandpipers (almost 4% of the estimated global population), in MClintock Bay alone, on May 18, 1997, was one of the highest ever one-day counts recorded in the Pacific/Yukon region. Other shorebirds that have been seen in high numbers include Lesser Yellowlegs and Common Snipe.

Other birds in the area include nesting Bald Eagle and Herring Gull, and landbirds, such as American Pipit, Horned Lark, Rusty Blackbird, and Lapland Longspurs (1,000 plus on one day) which can be seen in high concentrations during spring migration.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Trumpeter Swan Cygnus buccinator passage  1995  6,000 individuals  A4i  Least Concern 
Tundra Swan Cygnus columbianus passage  1995  12,000 individuals  A4i  Least Concern 
A4iii Species group - waterbirds non-breeding  20,000-49,999 individuals  unknown  A4iii   


IUCN habitat Habitat detail Extent (% of site)
Wetlands (inland) Freshwater lakes and pools; Freshwater marshes/swamps; Intertidal mud, sand or salt flats; Rivers  -

Land use

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

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: M'Clintock Bay to Lewes River Marsh. Downloaded from on 22/10/2016

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