780 U.S. NATIONAL MUSEUM BULLETIN 237 part 3 



also be found in drier upland fields. Though drainage of lowlands and 

 intensive cultivation appear recently to have reduced its breeding area 

 and numbers in parts of Iowa, Wisconsin, and Illinois, the bird has 

 adapted to man's agricultural practices by occupying unmowed 

 timothy-clover hayfields in Ohio, Illinois, Wisconsin, and possibly 

 elsewhere. Smith (1963) states that Henslow's sparrows abandon a 

 field when the grass is cut. 



Some of the birds commonly found nesting in the same environment 

 with the western Henslow's sparrow are: marsh hawk, ring-necked 

 pheasant, bobolink, meadowlark, red-winged blackbird, dickcissel, 

 and grasshopper and Savannah sparrows. Other species that fre- 

 quently nest near by and associate with it occasionally include: 

 greater prairie chicken, upland plover, horned lark, short-biUed marsh 

 wren, Traill's flycatcher, yeUow warbler, yellowthroat, and song and 

 swamp sparrows. 



Spring. — The western Henslow's sparrows usually leave their 

 southern wintering grounds in late March or early April. The latest 

 southern records are: South Carolina, March 28; Georgia, March 29; 

 Florida, April 11; Alabama, May 4; and Louisiana, May 15. Milton 

 Trautman (1956) observed a mass migratory flight of the species at 

 South Bass Island, Ohio, on April 21-22; the birds were moving in 

 company with juncos, and Savannah, swamp, song, chipping, field, 

 and fox sparrows. 



The earliest arrival dates in the north are: Shannon County, Mo., 

 March 19; DuPage County, III, March 28; and Sauk, Wis., April 7. 

 The following average arrival dates are given in the literature : Oberlin, 

 Ohio, April 29; Saginaw, Mich., April 22; Dane County, Wis., April 23; 

 Minnesota May 6; and South Dakota May 9. There are Nebraska 

 first records from April 22 to May 9. No data are available as to 

 when the bulk of the breeding population arrives in any area. Lynds 

 Jones (1892) noted that in Iowa "The first arrivals * * * are always 

 found in the underbrush skirting native woods. Later they move 

 out to their prairie homes." 



Territory. — Henslow's sparrows tend to live in loosely formed 

 colonies. They seem to establish territories within these colonies, but 

 the boundaries are not too rigid and may be violated occasionally. 

 Hyde (1939) observed fighting males "bowing to each other beak to 

 beak, like fighting roosters." He adds: "The fighting was apparently 

 not vicious; one bird flew at the other. Then they both disappeared 

 in the grass; shortly thereafter both birds separated and began sing- 

 ing — one fifty feet south of blind, the other from a tall weed not more 

 than twenty feet east of it." 



He thus described the population density of the colonies he studied 

 in southern Livingston County, Mich. : 



