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| Figure 9. The distribution of the Willow Flycatcher in Alberta. Click here for a detailed view of the distribution. |
McGillivray and Semenchuk (1998) reported the breeding distribution of the Willow Flycatcher in Alberta to range along the eastern slopes of the Rocky Mountains from the Bow Valley south to Waterton Lakes National Park. The bulk of the Alberta records for the Willow Flycatcher are south of the Bow Valley but records exist to the north to Jasper, although mainly in the Foothills rather than within the Rocky Mountains. Areas of high concentration of records are the Bow Valley, Sibbald Flats, and south of the Highwood Pass along Highway 40. The sites north of the Bow Valley would suggest that the range of the Willow Flycatcher could be expanded north towards Jasper and east towards Nordegg (Fig. 9). Forty-four percent of the sites we found in 1999 were within parks and protected areas. Pinel et al. (1993) notes a number of records north of Jasper up to the Kakwa-Grande Prairie area. Many dry upland sites that have historically had Willow Flycatcher records did not yield any sightings during our 1999 survey. In some areas of North America, there have been expansions of the Willow Flycatcher's range northwards (Stein 1963, Prescott 1987) but there is insufficient information to determine any range changes in Alberta.
Many published maps show the breeding distribution of the Willow Flycatcher as extending across the southern portion of Alberta, but there are no confirmed breeding records and only a few possible records from this area. A possible explanation would be that the eastern subspecies (E. traillii campestris) of the Willow Flycatcher in Saskatchewan and the western subspecies (E. traillii adastus) in British Columbia were assumed to meet in Alberta. The Breeding Bird Survey (BBS) also shows no records for Alberta in the south (Sauer et al. 1999). It is likely that southern Alberta represents a gap between the two subspecies which otherwise meet south of the Canadian border.
The Atlas of Breeding Birds of Alberta (Semenchuk 1992) 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, records of Willow Flycatchers migrating through and breeding in central Alberta continue to arise (Edgar T. Jones pers. comm.). 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 color differences and physical measurements (Seutin 1991, Pyle 1997) 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. A variation of the Eastern Phoebe's (Sayornis phoebe) song is remarkably similar to a fitz-bew (T. Thormin, pers. comm.). Tape recordings of the songs of Willow Flycatchers are virtually 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.
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| Figure 10. North American distribution of the Willow Flycatcher. Adapted from Dickinson 1999, Sauer et al. 1999. |
The Willow Flycatcher has a reported transcontinental breeding range from southern British Columbia, east across the southern prairies (but see note above for Alberta) east to Quebec and Maine. Its southern range limit is from the west coast in California and eastward across the southern United States to North Carolina and Virginia. A gap in the distribution from Montana south to Texas is apparent (Fig. 10). The Willow Flycatcher winters from Mexico to northwestern Colombia (DeGraaf and Rappole 1995).