12 



NORTH AMERICAN BIRDS. 



will')', 4.20; tail, 3.10, — total, about 7.50. Some speciniens slightly exceed 

 these dimensions ; few, if any, fall short of them. 



In autumn the upper surface is somewhat different from that in spring, 

 beino- less grayish, and with a tinge of rich sepia or snuti-browu, this 

 becoming gradually more appreciable on the tail. 



A specimen from Costa liica is uudistinguisliable from typical examples 

 from the Eastern United States. 



Habits. This species, first described in the ninth volume of the Pacific 

 Eailroad Surveys, bears so strong a resemblance to the Olive-backed Thrush 

 {T. swainsoni), that its value as a species has often been disputed. It was 

 first met with in Illinois. Since then numerous speciniens have been ob- 

 tained from the District of Columbia, from Labrador, and the lower 

 Mackenzie Eiver. In the latter regions it was found breeding abundantly. 

 It was also found in large numbers on the Anderson Kiver, but was rare 

 on the Yukon, as well as at Great Slave Lake, occurring there only as a 

 bird of passage to or from more northern breeding-grounds. 



In regard to its general habits but little is knmvn. Dr. Coues, who 

 found it in Labrador, breeding abundantly, speaks of meeting with a family 

 of these birds in a deep and thickly \\ooded ravine. The young were just 

 about to ily. The parents evinced the greatest anxiety for the safety of 

 their brood, endeavoring to lead him from their vicinity by fluttering from, 

 bush to bush, constantly uttering a melancholy phciKjh, in low whistling 

 tone. He mentions that all he saw uttered precisely the same note, and 

 were very timid, darting into the most impenetrable thickets. 



This thrush is a regular visitant to Massachusetts, both in its spring and 

 in its fall migration. It arrives from about the first to the middle of May, 

 and apparently remains about a week. It passes south about the first of 

 October. Occasionally it appears and is present in Massachusetts at the 

 same time with the Turd us swainsoni. From this species I hold it to be 

 unquestionably distinct, and in this opinion I am confirmed by the observa- 

 tions of two very careful and reliable ornithologists, ]\Ir. William Brewster 

 of Cambridge, one of our most promising young naturalists, and Mr. George 

 O. Welch of Lynn, whose experience and observations in the field are 

 unsurpassed. They inform me that there are observable between these 

 two forms certain well-marked and constant differences, that never fail 

 to indicate their distinctness with even greater precision than the constant 

 though less marked differences in their plumage. 



The Turclus alicim comes a few days the earlier, and is often in full song 

 when the T. swainsoni is silent. The song of the former is not onl\- 

 totally different from that of the latter, but also from that of all our 

 other Wood Thrushes. It most resembles the song of T. iMlla.si, but 

 differs in being its exact inverse, for whereas the latter begins with its 

 lowest notes and proceeds on an ascending scale, the former begins with 

 its highest, and concludes with its lowest note. The song of the T. simiu- 



