LAND BIRDS. 437 



taining single eggs of the Cowbird. It is also common to find a nest con- 

 taining two, three, or even four Cowbird's eggs along with one or more 

 eggs of the rightful owner. Ordinarily such nests are promptly deserted. 



The species most commonly imposed upon are the various warblers, 

 flycatchers, vireos and sparrows which nest in exposed situations where 

 the Cowbird can readily find them. Nevertheless, a very large number 

 of small birds suffer from the visits of the Cowbird, and a few species which 

 nest in the deep woods are frequently victimized, among them the Ovenbird. 

 Captain Bendire gives a list of ninety-one species and subspecies in whose 

 nests Cowbirds' eggs have been found, and states that undoubtedly a number 

 of others yet remain to be added to the list. In a few cases a bird thus 

 imposed upon builds a false bottom or shelf above the eggs of the intruder 

 and also raises the rim of the nest, thus leaving the Cowbird's egg to become 

 stale in the basement while it lays its own eggs above. This, however, 

 does not always secure safety, for the same or another Cowbird is likely 

 to visit the nest again and leave another egg. Such two-story nests are 

 not uncommon in collections, and occasionally even a three-story nest 

 is found. We have such a one, built by a yellow Warbler, in our college 

 collection. The Cowbird's eggs are variously speckled and spotted with 

 brown on a soiled white back-ground, often with a greenish tinge, and 

 average .81 by .66 inches. 



The Cowbird arrives from the south about the first of April. At Peters- 

 burg the earliest record is March 17, 1889 and the latest April 27, 1892. 

 At Grand Rapids the dates are April 1 to April 4, and at Sault Ste. Marie 

 the single record we have is April 22, 1901. The males come first, and often 

 singly or with flocks of other blackbirds, and it is not until nine or ten 

 days after their arrival that they are seen in flocks with the females. 



Their food has been carefully studied by the Division of Biological 

 Survey of the United States Department of Agriculture, and is found to 

 consist of about 22 percent of animal matter and 78 percent of vegetable 

 matter. Insects form about 20 percent of the food for the year, but are 

 mainly taken in INIay, June, July and August. The Cowbird appears to 

 eat few beneficial insects, avoiding the predaceous ground beetles, but 

 eating a few wasps, bees and ants. Its best work is in destroying grass- 

 hoppers which form about half the insect food, and in August make 45 

 percent of the entire food of the species. It also eats snout beetles or 

 weevils (about 2 percent), and caterpillars to about the same extent. 

 Among the latter are a few cutworms, and the armyworm (Leucania) was 

 found in four stomachs. Contrary to expectation it eats few flies or 

 maggots, and there is no proof whatever that it eats intestinal worms 

 from cattle droppings, or ticks from the animals themselves. In fact, 

 the association of this bird with cattle has never received any satisfactory 

 explanation. 



The vegetable food consists mainly of weed seeds and grain, the former 

 predominating. Many stomachs contained nothing but weed seeds and 

 clover seed, and many others nothing but these and grain. The latter is 

 largely waste grain, principally oats, but a considerable part is from newly 

 sown fields. The Cowbird does no harm to cultivated fruits. On the 

 whole its food would indicate that it is rather more beneficial than harmful. 

 It must not be forgotten, however, that in causing the death of multitudes 

 of small birds, all of which are valuable to the agriculturist, this blackbird 

 is doing an injury for which no amount of beneficial work in other directions 

 can ever atone. It is one of the few species of native birds which might 

 well be exterminated if possible. 



