168 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



furthermore, the haunts of the two, during the breeding season at least, 

 are quite different. 



Fall. — The russet-backed thrush spends a rather short season on its 

 breeding grounds. Mr. Willett tells me that it is not seen in southern 

 Alaska after late August; and Mr. Rathbun's notes indicate that it 

 disappears from western Washington during the first week in Septem- 

 ber. Most of these thrushes have probably left California before the 

 end of the latter month, though Professor Beal (1907) mentions speci- 

 mens taken there in October and even November. 



Winter. — The 1931 Check-list states that the russet-backed thrush 

 "winters from Vera Cruz, Guatemala, and Costa Rica to eastern 

 Ecuador and British Guiana," but it apparently does not go so far 

 south. Ludlow Griscom (1932) says: "The intensive collecting of the 

 last twenty years has failed to produce a single record of ustulata 

 anywhere in the New World south of Costa Rica. This fact was 

 correctly pointed out by Salvin in 1879, and ignored by everyone 

 since." 



In their report on the birds of El Salvador, Dickey and van Rossem 

 (1938) record it as a "common winter visitant throughout the higher 

 parts of the Arid Lower Tropical Zone and in lesser numbers in the 

 lowlands. Extreme dates of arrival and departure are October 14 and 

 March 15." They say further: 



The russet-backed thrush differs radically from the two olive-backs in that it 

 appears as a common winter visitant, while the olive-backs are, in the main, 

 migrants. The distribution of the present race is apparently general over the 

 whole of the hill country lying within the Arid Lower Tropical Zone. In the 

 lower country it is decidedly rare, for only two or three birds were noted in the 

 coyol-palm growth at Puerto del Triunfo in January, 1927. It is in the multitude 

 of berry- and fruit-bearing shade trees growing above the coffee that the russet- 

 backs are commonest. On Mt. Cacaguatique in November and December, 1925, 

 they literally swarmed in suitable localities; some trees had constantly arriving 

 and departing streams of these birds, with perhaps twenty-five or more in a tree 

 at once. 



Alexander F. Skutch has sent me the following interesting notes on 

 the winter haunts and behavior of this thrush in Central America: 



"On the Pacific slope of both Guatemala and Costa Rica — and 

 probably also in the intervening countries — the russet-backed thrush 

 winters in considerable numbers. It is particularly abundant in the 

 zone of heavy, humid forests between 2,000 and 4,000 feet above sea 

 level. Arriving in Guatemala early in October, and later in the month 

 in Costa Rica, it is at first shy, retiring, and little in evidence, although 

 occasionally a liquid quit reveals its presence in the dense under- 

 growth. After the beginning of the new year, it becomes an increas- 

 ingly prominent member of the avifauna. Thus on the Finca Moca, 

 a huge coffee plantation at the southern base of the Volcan Atitlan in 



