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| Figure 1. Willow Flycatcher feeding young. |
The Willow Flycatcher (Empidonax traillii, Fig.1), a member of the family Tyrannidae, is a small bird (length: 140 mm, weight: 11 g) that is associated with willows bushes and other deciduous shrubs in open habitats across North America. Until 1973, the American Ornithologist’s Union (AOU 1973) considered the Willow and the Alder Flycatcher (E. alnorum) as geographic variants of one species called the Traill’s Flycatcher. Before the split, it was thought that the Traill’s exhibited two song types; a two-note, fitz-bew, more common in the south and a three-note, fee-bee-o. Stein (1963) observed that sympatric populations of fitz-bews (Willows) and fee-bee-os (Alders) did not interbreed which led to the taxonomic split. Subsequently, Seutin and Simon (1988) found populations of Willow and Alder Flycatchers in southeastern Canada to be genetically distinct and reproductively isolated.
There is geographic variation within the Willow Flycatcher. Pyle (1997) recognizes five subspecies which differ in color, size and body proportions. In the southwestern United States, the subspecies E. traillii extimus has experienced a population crash due to loss or modification of riparian habitat primarily from cattle grazing, and reduced productivity due to Brown-headed Cowbird (Molothrus ater) parasitism. The distribution and abundance of the Willow Flycatcher populations in Alberta is poorly documented, in part due to the confusion of the split. This has led Alberta Environmental Protection to classify the Willow Flycatcher as "Status Undetermined" (Alberta Wildlife Management Division 1996). This category is for species whose information is insufficient to designate a status but are not known to be at risk.
Much of the data on habitat and distribution of Willow Flycatchers in Alberta described here is based on a forthcoming paper we are preparing from field work done in the summer of 1999.
This report summarizes recent and historical information gathered on the Willow Flycatcher in Alberta and elsewhere in order to provide an update on the status of the species in the province.