64 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



The individual pip notes are clear, but the effect of the rapid succession 

 is somewhat buzzy." 



The songs of the hybrid forms may be like the song of either parent 

 form, more often like that of the goldenwing, or a mixture of the two. 



The flight song, as heard by Frank A. Pitelka, is recorded as follows : 



Uee- 



zwe^- zwe4 



tsip- tzip- 



zee-zee-zee-zee-zee-zee- zee-zee-zee-zee-zee-zee- 



The song of the blue-winged warbler is one of the high-frequency 

 songs; Albert K. Brand (1938) gives the approximate mean as 7,675, 

 the highest note about 8,050 and the lowest note about 7,125 vibrations 

 per second ; this compares with an approximate mean for the blackpoll 

 warbler of 8,900 vibrations per second, the highest frequency of any 

 of the wood warblers, and an average for all passerine birds of about 

 4,000 vibrations per second. 



Field marks. — ^A small warbler with a greenish olive back, yellow 

 forehead and under parts, with a black line through the eye and two 

 white wing bars, is a blue-winged warbler. The female is merely 

 more dull in coloration than the male, and the young even duller. The 

 hybrids between this and the golden-winged warbler are more 

 puzzling, but in a general way they can be recognized; a nearly 

 typical blue-winged warbler with a black throat is probably a 

 Lawrence's warbler; and a golden-winged warbler without a black 

 throat or cheek and with a variable amount of white and yellow on 

 the under parts and in the wing-bars, is probably a Brewster's warbler. 

 But there is an immense amount of individual variation between the 

 two species, due to frequent crossing. 



Fall. — Most of the blue-winged warblers move southward during 

 August and September, though a few may linger in the southern part 

 of the breeding range into October. Professor Cooke (1904) says: 

 "Most of the individuals of the species migrate across the Gulf of 

 Mexico, apparently avoiding Florida on the east and Texas and 

 Vera Cruz on the west, as there is no record of the occurrence of 

 this warbler in fall in Texas, and but one in Florida — that of a bird 

 taken at Key West August 30, 1887." But this remains to be proved. 



Alexander F. Skutch writes to me: "This is another very rare 

 migrant in Central America. It has been recorded only a few times in 

 Guatemala and apparently not at all in Costa Eica. I have seen it 

 only once, on the Finca Moca, Guatemala, on October 30, 1934." 



Very little seems to be known about its winter distribution and still 

 less about its winter habits. 



