Brown-headed Cowbird: Molothrus ater ater (Boddaert).—Many individuals of this common summer resident overwinter in the southern part of the State and it is difficult to determine dates of arrival and departure in Kansas. Conspicuous abundance in the north covers the period April to October.
Breeding schedule.—The 141 instances of egg-laying span the period April 21 to July 20 ([Fig. 8]); the modal date of laying is May 15, and 53 per cent of all eggs are laid in the period May 11 to June 10. Inception of laying is here fairly reliably indicated, but in exceptionally early springs laying does occur earlier; a few eggs were found on April 6, 1963, too late for incorporation into this report other than in this sentence.
Number of eggs.—Clutch-size in cowbirds is not readily determined. On the basis of ovarian examination of five females taken in mid-season, the birds here lay about five eggs at a time. There is no question that the birds are "double-brooded" in Kansas, and the season is sufficiently long for as many as five "clutches" to be laid by a given female.
Eggs are laid in nests of some forty species of birds in Kansas; 39 of these are passerines. No preference for any one species is detectable; the most frequently parasitized species are simply the common species, and these are the kinds for which nesting records are easily gathered by man. In the following list of host species, the names marked with an asterisk are the conspicuously parasitized species.
Mourning Dove, Eastern Kingbird, Eastern Phoebe,* Say Phoebe,* Acadian Flycatcher, Barn Swallow, Horned Lark, Carolina Wren, Rock Wren, Brown Thrasher,* Mockingbird, Catbird, Wood Thrush,* Eastern Bluebird, Yellow-throated Vireo, Bell Vireo,* White-eyed Vireo,* Parula Warbler, Yellow Warbler, Black-and-white Warbler, Kentucky Warbler, Louisiana Waterthrush, Yellow-breasted Chat, Yellowthroat, Eastern Meadowlark, Western Meadowlark, Red-winged Blackbird,* Orchard Oriole,* Cardinal,* Black-headed Grosbeak, Indigo Bunting,* Blue Grosbeak, Dickcissel,* Pine Siskin,* Rufous-sided Towhee,* Grasshopper Sparrow, Lark Sparrow,* Chipping Sparrow, Field Sparrow.*
Scarlet Tanager: Piranga olivacea (Gmelin).—This rare summer resident in northeastern Kansas occurs in deciduous forest and bottomland timber. Specimens taken in the breeding season and records of nesting come from Clay, Doniphan, Douglas, Wyandotte, Johnson, and Linn counties, but the species probably occupies the entire eastern third of the State. Dates of arrival in spring are from April 29 to May 25 (the median is May 11), and dates of departure in autumn are from August 4 to September 23 (the median is August 10).
Breeding schedule.—Six records of breeding fall in the period May 11 to June 20.
Number of eggs.—Clutch-size is about 4 eggs.
Nests are placed 20 to 35 feet high in elm, linden, hickory, and walnut.
Summer Tanager: Piranga rubra rubra (Linnaeus).—This uncommon summer resident in eastern Kansas occurs in woodland. Specimens taken in the breeding season and records of nesting come from east of stations in Doniphan, Shawnee, and Montgomery counties. Dates of arrival in spring run from April 24 to May 18 (the median is April 29), and the species departs southward in September and October.