272 NESTS AND EGGS OF 



der ; the general effect being that of a dark, heavily-colored egg. Ten 

 specimens measure: -79X.55, . Sox. 55, .86x.6o, .84X.63, .Syx^S, .87 

 x.6i, .88x.66, .86x.6i, .83x.6o, .85x.6o. An average specimen 

 measures .85 x .64. 



495. Molothrus ater (BODD.) [258.] 



Cowbird. 



Hab. Whole of the United States, north into Southern British Columbia, south in winter to Mexico. 



Known as the Cow Bunting or Cow Blackbird from its habit of 

 alighting on the backs of cows or cattle, where it sits contentedly 

 while they are grazing. It is a notorious parasite, and does 

 not build a nest, but like the European Cuckoo, lays its eggs 

 in the nests of other birds, usually in those of species smaller 

 than itself. Generally a single egg is deposited, and as many 

 as< five have been found in a nest. The exact number the female lays 

 is not known. Eggs of this bird are subject to great variation in 

 their size and markings, and when found in the nests of such birds 

 as the Cardinal Redbird, Towhee Bunting, Meadow Lark and Brown 

 Thrasher,* it is sometimes difficult to readily distinguish "which 

 is which." Yet it should not be understood that the Cowbird's eggs 

 look exactly like those of the species just mentioned, for they really 

 have, on the whole, only a faint resemblance to them, and when a 

 large series of either species is brought together and compared with 

 those of the Cowbird the difference is at once apparent. Dr. Jones 

 suggests that when the egg of the Cowbird resembles so closely the 

 eggs in the nest where it has been laid, as to make identification un- 

 certain, it is a good plan to blow all the eggs and notice if the sus- 

 pected egg has a yelk of different tint from the balance of the set. 

 If it has, it is strong evidence that it was laid by an intruder, for 

 almost invariably eggs of the same set have the same tinted yelks. 



The ground-color of the Cowbird's egg is white or gray, sometimes 

 obscured by the abundance of markings.' Spots, specks and blotches are 

 generally pretty evenly distributed over the entire surface. The mark- 

 ings vary from a chocolate-brown to those of a reddish and yellowish- 

 brown. The whole surface of an egg is often quite densely marked 

 with specks the size of a pin point, while the shell of other specimens 



* Besides those above named the following are some of the nests in which the Cowbird's eggs have 

 been found: Blue-gray Gnatcatcher, Black and White Warbler, Blue-yellow-backed Warbler (Parula), Worm- 

 eating Warbler, Prothonotary Warbler, Maryland Yellow-throat, Yellow Warbler, House Wren, Warbling, 

 Yellow-throated and Red-eyed Vireos, Indigo Bunting, Chipping Sparrow, American Goldfinch, Song Spar- 

 row, Swamp Sparrow, Slate-colored Junco, Oven Bird, Pewee, Wood Pewee, Acadian and Traill's Flycatchers, 

 Black-throated Bunting, European House Sparrow (Passer domesticus], Yellow-breasted Chat, Bluebird, 

 Orchard, Baltimore, Bullock's and Hooded Orioles, Scarlet Tanager, Kingbird, Towhee, Prairie Horned 

 Lark (Otocoris alpestris praticola], Wilson's Thrush, Wood Thrush, Red-headed Woodpecker, Robin and 

 Mourning Dove. 



