By Cameron D. Eckert

Since 1995, Yukon biologists have worked to document and understand the rich and varied ecosystems of the La Biche and Beaver River Valleys in the extreme southeast Yukon. In June 1998, an effort was made to access previously unexplored forests along the upper La Biche River and higher elevation subalpine habitats of the adjacent Kotaneelee Range. A section of the Yukon-Northwest Territories border follows the height of land along the southern extent of the Kotaneelee Range. On June 19, we established a study site (60o14'45"N/124o08'07") at treeline (elevation 1200 metres) on the west (Yukon) side of the Kotaneelee Range just a few hundred metres from the border. The habitat at this location was transitional from relatively closed coniferous forests dominated by Subalpine Fir Abies lasiocarpa, with some White Spruce Picea glauca, Lodgepole Pine Pinus contorta, and Trembling Aspen Populus tremuloides, through open coniferous dominated forest with patches of dense tall shrubs, primarily alder Alnus crispa and willows Salix glauca and S. barclayii and low shrubs, primarily birch Betula glandulosa and B. occidentalis in drier areas, to higher elevation alpine tundra with scattered patches of low shrubs. The wet drainages supported dense tall shrubs and some relatively small patches of Balsam Poplar Populus balsamifera, and Mountain Ash Sorbus scopulina. The transitional nature of this location was reflected by the fact that from our camp three Zonotrichia species, White-throated Sparrow Z. albicollis, White-crowned Sparrow Z. leucophrys, and Golden-crowned Sparrow Z. atricapilla could be heard singing on territories.

On the evening of June 19, I heard a part of an Empidonax song which I suspected was that of a Dusky Flycatcher, Empidonax oberholseri. However, the bird did not sing again and it became apparent that we would have to wait until the following morning to confirm the discovery. At dawn on June 20, Mike Gill and I returned to the location and immediately found a Dusky Flycatcher in full song. During our subsequent surveys that morning we determined that there were at least four Duskies singing within a few hundred metres of our camp. Recordings of the songs were made and are on file with the Canadian Wildlife Service.

Since Swarth's (1926) early work, it has been known that in the north, Dusky Flycatchers typically occur at significantly higher elevations (800-1200 metres) than Hammond's Flycatchers which are limited to lowland deciduous forests usually along rivers. Currently there are no known Yukon locations where Dusky and Hammond's Flycatchers occur together. The habitat used by Dusky Flycatchers at our study site in the Kotaneelees was typical of other treeline locations where this species is found in the Yukon. The Duskies were found in tall (approximately 2 metres), dense shrubs (alders and willows) along wet draws in open forest habitat.

Hammond's E. hammondii, Least E. minimus, and Alder E. alnorum Flycatchers are all common in the lowland forests and shrub habitats of the La Biche and Beaver River Valleys, and in 1995 we observed one Yellow-bellied Flycatcher E. flaviventris along the Beaver River. This was the first time we observed Dusky Flycatcher in our study area. The nearest Yukon location where Dusky Flycatchers are found is approximately 360 km west at treeline in the Cassiar Mountains near Rancheria Falls, and in British Columbia approximately 180 km southeast at Fort Nelson (Campbell et. al. 1997). While Dusky Flycatcher has not been documented in Northwest Territories (Sirois and McRae 1994), it should be looked for at treeline on the east (N.W.T.) side of the Kotaneelee Range just a kilometre or so from our study site.

Our discovery of Dusky Flycatchers in the Kotaneelees is part of an ongoing study which has found that the forest and wetland habitats of the La Biche and Beaver River Valleys support exceptionally rich and productive bird, wildlife and plant communities. While it is clear that there is no other area like it in the Yukon, we are now recognizing that in many ways the area is unique on a much broader spatial scale. Given the continued onslaught of industrial interests (logging and oil & gas) in the region, it is critical that the La Biche and Beaver River Valleys be made high priority candidates for protection with significant areas set aside immediately to allow for long-term conservation.

Acknowledgments

This study was funded by Yukon Territory Government, Department of Renewable Resources, Parks and Habitat Branches and the Canadian Wildlife Service, Whitehorse, Yukon. In 1998, bird surveys were conducted by Cameron Eckert and Mike Gill and vegetation surveys were conducted by Jennifer Staniforth, Bruce Bennett and Rhonda Rosie. Mike Gill and Pam Sinclair kindly reviewed a draft of this note.

References

Campbell, R.W., Dawe, N.K., McTaggart-Cowan, I., Cooper, J.M., Kaiser, G.W., McNall, C.E., and G.E.J. Smith. 1997. The Birds of British Columbia, Volume 3, Passerines: Flycatchers through Vireos. UBC Press, Vancouver, B.C., Canada.

Sirois, J. and R.D. McRae. 1994. The Birds of the Northwest Territories, Canada. Environment Canada, Canadian Wildlife Service. Yellowknife, NT.

Swarth, H.S. 1926. Report on a collection of birds and mammals from the Atlin region, northern British Columbia. University of California Publications in Zoology 24:51-162.

This article originally appeared in Birders Journal. Reference as:

Eckert, C.D. 1998. Known range of Dusky Flycatcher extended northeast to the Kotaneelee Range, Yukon. Birders Journal 7(4):205-207.

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