The breeding distribution of the Willow Flycatcher in Alberta ranges along the eastern slopes of the
Rocky Mountains from the Bow Valley south to
Waterton Lakes National
Park. Areas of high concentration of records are the Bow Valley, Sibbald Flats, and south of the Highwood Pass along Highway 40. The bulk of the Alberta records for the Willow Flycatcher are south of the Bow Valley. Breeding records suggest its range extends north to Jasper and east towards
Nordegg, although mainly in the Foothills rather than in the Rocky Mountains. In some areas of North America there have been expansions of the Willow Flycatcher's range northwards, but there is insufficient information to determine any range changes in Alberta.
Many published maps show the Willow Flycatcher's breeding distribution extending across the southern portion of Alberta, but there are no confirmed and only a few possible breeding records from this area. It is likely that southern Alberta represents a gap between the eastern subspecies that occurs in Saskatchewan and the western subspecies that occurs in British Columbia, which otherwise meet south of the Canadian border. The Breeding Bird Survey (BBS) also shows no records for Alberta in the south.
The Atlas of Breeding Birds of Alberta produced relatively few confirmed breeding records for the Willow Flycatcher. Several observations were significantly north and east of the expected range. In addition to the Atlas data, Willow Flycatchers migrating through and breeding in central Alberta have been reported. Some experts argue that these extralimital records are misidentifications. The lack of supporting evidence in the form of recorded vocalizations and the uncertainty surrounding the reliability of identification by colour differences and physical measurements makes the inclusion of these records in this status update problematic. Experienced birders acknowledge that the distinction between the Alder and Willow Flycatcher's call is not as clear-cut as some commercial recordings would suggest. For instance, a variation of the Eastern Phoebe's song is remarkably similar to the Willow Flycatcher
"fitz-bew". Tape recordings of the songs of Willow Flycatchers are effectively a requirement before extralimital observations can be authenticated. Consequently, we are reluctant to consider any records outside of the eastern slopes region as confirmed Willow Flycatcher records.
Reprinted from Alberta Wildlife Status Report No. 29
with permission from Alberta
Sustainable Resource Development.