FLYCATCHERS. 295 



bushy, swampy fields. Unlike many other Flycatchers, they 

 are somewhat shy of man's approach. They usually remain 

 within fifteen feet of the ground, but they sometimes take 

 both higher and longer flights than I have ever known the 

 Least Flycatchers to take. They are in fact much less 

 stationary than most of their relations, though their general 

 habits are the same. They live much on the edges of the 

 woods, and often occur along the roadsides, where, from the 

 tops of the bushes and lower trees, they utter their peculiar 

 notes. I have been led, partly from observations on this 

 species, to believe that probably the line separating \rf>o faunae, 

 (such as the Alleghanian and Canadian i"^) can never be pre- 

 cisely defined, since birds of the same district vary considerably 

 in their latitudinal range. This is the case even in more 

 or less restricted localities. While walking southward 

 through the Crawford Notch, I saw or heard TraiU's Fly- 

 catchers from the Willey House to a point several miles 

 nearer Conway, and beyond this point the Least Flycatchers 

 (who are comparatively rare in the Canadian district) were 

 soon heard. No more of the former were seen, but the 

 latter were frequently observable down to North Conway, 

 where (at least in one grove) the Swainson's Thrushes and 

 Black-throated Blue Warblers were apparently common. The 

 dividing line, already spoken of, must necessarily be irreg- 

 ular, because affected by altitude as well as latitude. Among 

 the White Mountains, one often finds it quite sharply de- 

 fined by the general face of nature and by the atmosphere. 



The Traill's Flycatchers do not, so far as I know, occur 

 near Boston in autumn, and it is probable that they return 

 to the South by an inland route,* as is the case with many 

 other birds. 



d. Their ordinary note is a slightly querulous pu, which 

 is often repeated, and which recalls the voice of the Great 

 Crested Flycatcher. Another note is pu-ee, which is uttered 

 in a peculiar tone, very distinct from that of the Wood 



^"^ See § 17, VI, A, v. plumage which was shot at Camhridg-e, 



* This is prohahly true as a rule ; Massachusetts, August 24, 1875. — 

 but I have a young bird in full autumn W. B. 



