NORTHERN PRAIRIE WARBLER 435 



found that the opening four notes, all on the same pitch, were almost 

 precisely alike except that the warbler's were simple, tee^ tee^ tee^ tee^ 

 while the sparrow's were slightly dissyllabic, fwee^ fwee^ fwee^ fwee. 

 The pitch, tone, and quality were the same. The rest of the warbler's 

 song went up the chromatic scale characteristically, while the spar- 

 row's ended with a descending trill. The two birds kept near to- 

 gether and sang antiphonally, or apparently so. This seemed like a 

 clear case of imitation on the part of the prairie warbler." More 

 likely this was one of the variations in the warbler's songs, as described 

 by Mr. Saunders, rather than an imitation. 



Field marks. — The prairie warbler should be easily recognized, as 

 it is distinctively marked, with its bright-yellow under parts, more or 

 less streaked with black on the sides, two yellowish wing bands, and 

 largely white outer tail feathers. The chestnut marks on the back 

 are not always very conspicuous. Females and winter birds are not 

 much different, merely duller in colors. The song is easily recognized. 



Enemies. — The northern prairie warbler is a common victim of the 

 cowbird. Dr. Friedmann (1929) had 10 records from its limited 

 range, in the eastern States, Harold H. Bailey (1925) says that the 

 nest is often abandoned after the cowbird's egg is laid in it, but that 

 "often this warbler has been known to construct a false bottom over 

 the Cow-bird egg, and any of her own that were in the nest, as well, 

 and start laying again." Harold S. Peters (1936) lists as external 

 parasites of the northern prairie warbler a louse, Ricinus pallens 

 (Kellogg) , and a tick, HaemaphysaUs leporis-palustris Packard. 



Fall. — In Massachusetts, the southward migration begins early. As 

 soon as the young are fully grown the family parties wander about in 

 the brushy pastures during July, and after molting some of them start 

 south before the end of that month. The migration is well under way 

 during August, very few remaining in September. In the more south- 

 ern States, the migration continues from the middle of August until 

 the first week in November. It has been recorded in northern Florida 

 as early as July 27, and has struck the light on Sombrero Key as early 

 as August 1 and as late as November 4, indicating a much-prolonged 

 migration season. 



Winter. — A few northern prairie warblers may winter in the south- 

 ern half of Florida, but probably most of the wintering birds in 

 Florida are of the southern race. The main winter home of the north- 

 ern birds is in the Bahamas and the West Indies. C. J. Maynard 

 (1896) writes: "The Prairie Warblers were very abundant in the 

 dense thickets on the island of Key West during the autumn and early 

 winter of 1870. The}^ frequented the drier portions of the Key but 

 did not sing." Those that he reported in the mangroves along the 

 coast of the mainland were probably Florida prairie warblers, which 



