1484 U.S. NATIONAL MUSEUM BULLETIN 237 part 3 



They enter traps with ground entrances more readily than those with 

 top entrances. 



Field marks. — Adult birds are readily separable from other sparrows 

 in the field by their dark, chunky aspect, their reddish cap and wings, 

 clear gray breast, and white throat. Other aids to identification are 

 the hard call notes that have the quality of cut-glass percussion, and 

 the bird's characteristic manner of pumping the tail in flight. Juvenile 

 birds in summer are easily confused with young song sparrows and 

 young Lincoln's sparrows, for all have similar fine breast streakings, 

 but as R. T. Peterson (1947) points out, the juvenal swamp sparrow 

 is "usually darker on the back and redder on the wings." In the hand 

 the swamp sparrow's smaller and more curving bill is diagnostic, as is its 

 smaller size and, according to Olive P. Wetherbee (pel's, com.), its softer 

 texture to the touch. 



Enemies. — The main decimating factor of swamp sparrow popula- 

 tions on the breeding grounds are those related to changing water- 

 levels, both natural and man-induced. While the creation of mill 

 ponds and other bodies of water by artificial damming during the 19th 

 century probably increased the range and density of the swamp 

 sparrow within and beyond the glaciated areas of North America, 

 the draining of morasses for housing developments is currently re- 

 ducing its habitat markedly. 



As the swamp sparrow usually nests just above the water level, a 

 rise of only a few inches in that level can drown out every nest over 

 wide areas. E. H. Eaton (1910) records that the birds had their nests 

 thus flooded out in New York twice in 1906. I observed the same 

 thing in Connecticut in 1956. Each year the birds take two or three 

 of these 20-day gambles, that the waters will not rise until their young 

 are fledged. 



Herbert Friedmann (1963) states: 



The swamp sparrow is generally an uncommon victim of the brown-headed 

 cowbird. * * * Although the cowbird frequents marshes during migration, it 

 tends to leave marsh nests alone. At Ithaca, New York, where both the swamp 

 sparrow and the cowbird are common, there were no records of parasitism on the 

 species. 



* * * In Michigan, Berger (1951, p. 28) reported an unusual degree of parasit- 

 ism on the swamp sparrow: he observed five nests, four of which had been vic- 

 timized by the cowbird. 



Although the swamp sparrow appears to be a rather uncommon victim of the 

 brown-headed cowbird in most areas where the two exist together, it has been 

 found to be a frequent and submissive host in southern Quebec. Here L. M. 

 Terrill (1961, p. 10), between 1897 and 1956, found 322 nests of the swamp sparrow, 

 of which 34, or roughly 10 percent, contained eggs of the cowbird. He wrote 

 that the swamp sparrows in his area nested chiefly in sedgy tussocks among small 

 willows in shallow water. Apparently this environment was more acceptable to 

 the cowbirds than are the usual marshy areas. 



