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The Mackenzie River delta is an immense area of low-lying waters and deltaic islands that is situated just east of the Yukon/Northwest Territories border along the coast. The area includes Shallow Bay, Olivier, Ellice, Pelly and Kendall islands, as well as part of Richards Island. Much of the area is covered by fluvial deposits of silt and sand. The islands are generally marshy and covered in sedges, grasses, and horsetail, but there are shrubs in higher areas. Levees have formed along the shores of islands as a result of spring flooding. The lowlands of Richards Island are dotted with numerous lakes and ponds and contain several pingos. More than 5,000 Beluga Whales calve in the Mackenzie River estuary, and the outer islands support a significant population of Barren-ground Grizzly Bears.
The islands in the outer Mackenzie River delta are important staging grounds from late August to late September for several species of geese and Tundra Swans. Large numbers of shorebirds migrate through the delta, but the extent of use is unknown. Depending on the weather, moderate to large numbers of Lesser Snow Geese congregate in the delta just prior to southward migration. In years when the Yukon and Alaskan north slopes are snow-covered, such as 1975, numbers can reach 323,000 (152,350 adults and 170,650 young) and the birds will stay for longer periods of time. This is about a fifth of the 1.5 million Lesser Snow Geese estimated to exist in 1975. In other years fewer (but still large) numbers were seen (15,000 adults, 10,000 young, 1973/4/6 average). The most important areas for staging Snow Geese are around Shallow Bay and northern Olivier and Ellice islands.
Peak numbers of staging Greater White-fronted Geese have ranged from 12,500 to 23,700 birds between 1973 and 1976. This represents between 1and 2% of the North American Greater White-fronted Goose population. This species occurs mostly in the Shallow Bay area.
It likely that a large proportion of the Black Brant population migrates through the outer Mackenzie Delta, but stopovers are probably short in duration and thus numbers are not well known. Up to 6,112 Brant were seen during single surveys conducted between 1973 and 1976 (2% of North American Brant and 5% of Black Brant).
Peak fall numbers of Tundra Swans have ranged from 1,900 to 3,100 birds. This is 1% of the current North American Tundra Swan population. This species concentrates around Malik Bay, Swan Channel, the outer section of Kendall Island MBS and eastern Shallow Bay.
During the breeding season a variable-sized colony of Lesser Snow Geese is found on small islands south of Kendall Island. At most, 8,000 birds have been recorded breeding here. Approximately 2,500 Tundra Swans, 2,800 Greater White-fronted Geese, as well as Sandhill Cranes, Brant, Glaucous Gulls, Arctic Terns, dabbling ducks, and shorebirds nest and moult in the area.
BirdLife International (2020) Important Bird Areas factsheet: Mackenzie River Delta. Downloaded from http://www.birdlife.org on 08/07/2020.