The Nisutlin River flows into Teslin lake in south-central Yukon. Here, the river widens into a 4 km wide delta, with a mosaic of wetlands and meandering river channels. In the late spring and early summer, the water levels on Teslin Lake are very high with the delta being mostly submerged. As a result, only limited numbers of waterbirds use the delta for nesting. In late summer and fall, however, the water level drops rapidly, exposing a series of mudflats and plant communities characterized by dense emergent, floating, and submerged vegetation. This late summer drop in water levels is in stark contrast to the regime in other large headwater lakes of the southern Yukon River Basin. As a result the Nisutlin River Delta is one of southern Yukon's most important congregation areas for migratory waterfowl in the fall.
During fall migration, regular one-day peak counts of over 1,000 Tundra Swans and up to 40 Trumpeter Swans have been recorded on the delta. In all, as many as 2,000 swans have recently been recorded on a single day. The lower 80 km of the Nistulin River valley also supports a breeding population of Trumpeter Swans with about 10 to 12 breeding pairs being recorded in 1997 (this would be just below the 1% national threshold if they were known to be the Rocky Mountain population). This is one of the larger concentrations of breeding Trumpeter Swans in Canada. In addition to swans, up to 10,000 waterfowl (both ducks and geese) stage on the delta during fall migration.
The delta also provides feeding habitat for migrating Peregrine Falcons (ssp. anatum - nationally endangered) and Short-eared Owls (nationally vulnerable). Habitat for an additional 12 species identified as at risk in the Yukon is also provided by the delta.
BirdLife International (2020) Important Bird Areas factsheet: Nisultin River Delta. Downloaded from http://www.birdlife.org on 25/10/2020.