LEAST FLYCATCHER (Empidonax minimus) LEFL Sample size: 217 |
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The Least Flycatcher is a fairly common Empidonax species, breeding predominantly in northern North America. It breeds from southwest Newfoundland in the northeast, to the Yukon in the northwest. In the south, its range extends from northern New Jersey through Wyoming, reaching its southernmost extent in the southern Appalachians [Briskie 1994 (BNA)]. This species is a complete migrant, wintering in Central America from both coasts of Mexico to Nicaragua [AOU 1998]. A small population also winters in southern Florida [Phillips and Lanyon 1970]. These birds are strongly territorial in both summer and winter and are known to be quite aggressive around their nests [Bent 1942, Briskie 1994]. Least Flycatchers nest in a variety of deciduous woodlands, but are most often found near openings and forest edges [Bent 1942]. A decline in the species has been observed in eastern North America where forests and urban development have replaced the abundant old fields of the agricultural boom [Veit and Petersen 1993]. From 1966-1991, there has been an overall decline east of the Mississippi R. of 34.9% [Sauer et al. 2001].
Quite a bit of research has focused on migration in this species. Least Flycatchers appear to use two main migratory routes: one through the eastern and Gulf states and the second through the central U.S., from the Rockies to the Mississippi Valley [Briskie 1994 (BNA)]. In addition, a small number of migrants regularly pass through the western U.S. [AOU 1998]. In spring, migrants arrive in the southern U.S. between late March and mid-April [Briskie 1994 (BNA)] and reach their northernmost breeding grounds in late May [Bent 1942]. In Massachusetts, peak numbers of migrants are typically recorded in late May [Veit and Petersen 1993]. Least Flycatchers arrive earlier in spring than other eastern Empidonax species, by an average of 11-14 days in Massachusetts [Veit and Petersen 1993]. In addition, males arrive approximately 6 days before females and adults may arrive before second-year birds [Hussell 1981].
Fall migration is quite early in Least Flycatchers, resulting in a very short time spent on the breeding grounds. It has been estimated that adults spend about 64 days on the breeding grounds [Hussell 1981], of which approximately 58 are needed to raise a brood [Sealy and Biermann 1983]. These flycatchers begin departing their northern breeding grounds by the end of July, with adults leaving considerably earlier than immatures [Briskie 1994 (BNA)]. There does not appear to be a difference in the timing of fall migration between the sexes [Briskie 1994 (BNA)]. Fall migration of this species peaks in late August in Massachusetts [Veit and Petersen 1993], although some individuals have already reached their Guatemala wintering grounds by this time [Griscom in Johnson 1963].
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Observations
This earliest migrating of all the small "Empidonax" flycatchers had a low sample size (217) in our study. No differences were detected between A, B or C sites, nor between the four states. The very earliest migrants showed up in periods 1 and 2. However, most arrived during period 3 in all states, peaking in periods 4 and 5.
With fewer birds in the valley as a whole, most transects recorded no Least Flycatchers. At certain places during periods 4 and 5 however, clumps of migrants were recorded on the transects. The maxima were 10 birds in period 4 at C sites in both VT and CT. |
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LEFL Map
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