THE COWBIRD. 293 
to bear out this supposition. The insects that annoy the animals do 
not constitute any considerable portion of the cowbird’s food, nor are 
the seeds upon which it subsists found to any particular extent where 
cattle range. As the cowbird is abundant in the Mississippi Valley 
and on the Great Plains, it would be interesting to know if it for- 
merly associated on familiar terms with the buffalo, and such would 
seem to be the case, as Major Bendire gives ‘ buffalo bird’ as one of 
its former names.? 
The cowbird ranges from the Atlantic to the Rocky Mountains and 
sparingly beyond nearly to the Pacific, and from the Gulf of Mexico 
‘northward into southern Canada. It breeds throughout its range, 
except in the immediate vicinity of the Gulf. 
In winter most of the birds leave the United States and pass into 
northern Mexico, but a few remain in the Southern States and strag- 
glers may occasionally be found farther north. The southward 
movement begins in September, and by November 1 the birds have 
left the Northern States. On their return in spring they appear in 
the Middle States in March, and by the first week in May have coy- 
ered their whole summer range. Their great center of abundance is 
the Mississippi Valley, where they are among the commonest species 
and second to few in point of numbers. It is a well-known fact that 
the cowbird, like the European cuckoo, but unlike most other birds, 
builds no nest for its eggs and young, but saddles the labor of rearing 
its progeny upon other species into whose nests it introduces its eges. 
The birds it selects for this imposition are mostly species smaller than 
itself, and such as nest in bushes and hedges, or near the borders of 
woodland; for as the cowbirds inhabit the open country they will not 
penetrate the depths of the forest. Most of the birds thus imposed 
upon accept the charge, however reluctantly, and rear the intruder. 
As the cowbird’s egg usually hatches before the eggs of the owner of 
the nest, the young cowbird begins at once to grow and crowds out, 
or prevents further incubation of, the other eggs; or, if they are 
hatched, so monopolizes the food supply that the young soon perish of 
starvation. This has been observed many times, but whether it is the 
universal rule has not yet been demonstrated. It is supposed that a 
female cowbird deposits but one egg in a nest, and that where more 
than one strange egg is found they are the product of different birds. 
As many as seven cowbird eggs have been found in one nest. A few 
birds actively resent the intrusion of the strange egg, and either 
desert the nest entirely, or build up its sides and lay a new floor, 
beneath which the unwelcome present is left to decay. This device 
has, in some cases, been used twice in the same nest, a three-storied 
structure resulting, in the upper story of which the rightful occupants 
were finally reared. The sparrows, warbiers, and flycatchers are the 
1 Rept. U. 8. National Museum for 1893, p. 591, 1895. 
