Throughout the five census years of the Breeding Bird Atlas Project (1987-1991), only two confirmed breeding records were reported. There were remarkably few observations of this species with most concentrated in the Bow Valley from west of Calgary to Banff. Holroyd and Van Tighem (1983) recorded the Willow as a fairly common summer resident in the mountain parks. By contrast, the Provincial Museum of Alberta (PMA) collection has only a handful of specimens to document the presence of this species in Alberta. In 1999, we found over 30 Willow Flycatcher sites in a census from Waterton to Jasper. The average number of males singing per site was two. These sites represent a sizable fraction of the accessible sites in the province. It is difficult to estimate the extent of available habitat because unlike forested habitats, willow swales have no commercial interest and are not mapped. Undoubtedly the province supports more than 100 pairs but given the lack of reports for this species it is unlikely that the provincial population is greater than 250 pairs.
There has been no published study in Alberta examining population trends. BBS data provides a rough estimate of population trends and the evidence for this species in Alberta is not encouraging (Fig. 11). The Canadian Breeding Bird Survey (Downes et al. 1999) reports Alberta’s Willow Flycatchers have experienced a 0.8% mean annual drop in population (number of routes used to calculate trend = 66) from 1966-1996. Although this trend is not statistically significant (P> 0.15), it represents the highest provincial decline for the species in Canada.
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| Figure 11. Index of population change of the Willow Flycatcher in Alberta and Canada, 1966-1996. Data from Canadian Breeding Bird Survey (modified from Downes et al. 1999). |
From 1966 to 1996, Manitoba, Nova Scotia and New Brunswick have experienced declines in BBS reports of the Willow Flycatcher while British Columbia, Saskatchewan, Ontario and Quebec have experienced increases (Downes et al. 1999). Ontario's 2.3% growth in reports is the only trend which is thought to be statistically significant (P <0.05). Campbell et al. (1997) notes that the Willow Flycatcher is expanding its range south and east in British Columbia. The Willow ranges from "very rare" on Vancouver Island to "uncommon" to "fairly common" in the British Columbia interior (Campbell et al. 1997). Smith (1996) reports the Willow Flycatcher to be "uncommon" in southern Saskatchewan with rarity increasing north to central Saskatchewan. The Willow Flycatcher is "uncommon" in the extreme southwest and "rare" elsewhere in southern Manitoba (Rudolf Koes, pers. comm). Only three confirmed nest records for the Willow in Manitoba are reported by De Smet and Conrad (1988). From 1966 to 1996, Canada has experienced an overall 0.6% growth in reports of Willow Flycatchers for the BBS (Downes et al. 1999).
In the southwestern United States, the estimated size of the endangered E. traillii extimus population is between 300 and 500 pairs (Sogge et al. 1997). Significant growth in Willow Flycatcher populations has occurred in Oregon due to willow habitat preservation and a reduction of cattle grazing (Taylor and Littlefield 1986). Zink and Fall (1981) found Willow Flycatchers to be "common" in suitable habitat in southern Minnesota. The Willow Flycatcher ranges from "common" to "uncommon" in North Dakota (Stewart 1975) and "fairly common" in South Dakota (Peterson 1995). Boone and Krohn (1998) list the Willow as "common" with a "stable" population trend in Maine.