Description 



SIZE 



The Swainson's Warbler is a rather short and stocky bird. Its 

 length, 5 to 51/^ inches, is about average for warblers, but it is 

 heavier than most of the Dendroicas and Verrnivoras.- Four males 

 collected during the breeding season weighed 13,2, 15.4, 16.2, and 

 16.6 grams (Mengel, 1965; Norris and Johnston, 1958; and L. C. 

 Binford, Louisiana State University Collection), Two females 

 taken in winter, one in Quintana Roo, Mexico, and one in British 

 Honduras, weighed 13.7 and 13.9 grams (L. C. Binford and S. M. 

 Russell, Louisiana State University Collection). A live male at 

 Andros Island, Bahamas, in March, weighed 15.6 grams (Walkin- 

 shaw and Walkinshaw, 1961). 



A series of birds that struck a Tallahassee, Fla., TV tower in 

 spring migration averaged lighter than those striking the tower 

 in the fall. The mean weight of the spring series of 15 birds was 

 14.9 grams, whereas the mean weight of the fall series of 19 was 

 18.9 grams (table 1). The Tallahassee TV tower is less than 50 

 miles from the Gulf Coast, and birds coming in from a trans-Gulf 

 or circum-Gulf migration would have used up much of their re- 

 serve fat; whereas those leaving the United States would have a 

 large fat reserve for the long journey to the wintering ground. 

 Norris (1963, p. 47) reported that two birds that struck a TV 

 tower in the Savannah River Valley in South Carolina on Septem- 

 ber 24, 1957, were excessively fat : one was recorded as having 19 

 percent fat, and the other, 24 percent. 



Table 1. — Weights of Swainson's Warblers killed at TV tower, Tallahassee, 



Fla., during migration 



[In grams] 



Spring Fall 

 (15 specimens) (19 specimens) 



Minimum 





11.3 



14.3 



Maximum 





. 15.7 



20.4 



Mean 





14.9 



18.9 



Median 





13.9 



18.3 

 ±1.7 



Standard deviation ... 





±1.2 



43 



