NOkfH AMERICAk BIRDS. 279 



pecker (Bphyrapicus rarius), does live to a considerable extent upon this sap. Ob- 

 servation does not show that other species have the same habit, but it Is a difficult 

 point to decide by dissection, as fluid contents disappear quickly from the stomach. 

 Many observers have testified to the good work these birds do in destroying insects, 

 -while others have spoken of harm done to fruit or grain. Both are correct within 

 certain limits. Field observation on the food habits of birds is attended with so 

 many difficulties as to render It a very unreliable source from which to draw general 

 conclusions. The most conscientious and careful person is often deceived, not only 

 as to the quantity of a particular kind of food eaten by a bird, but 

 as to the fact that it is eaten at all. The further difficulty of keeping a number of • 

 birds, or even a single oJe, under constant observation makes an estimate of relative 

 proportions of different kinds of food impossible. When much mischief is done 

 the fact is apparent, but there is no way to find out how much good is done during 

 the same time. For these reasons it often happens that reports on food habits, 

 based on observations of wild birds, not only confiict with each other, but also disa- 

 gree with the results obtained from stomach examinations. This last method 

 must be taken as the court of final appeal, and it is evident that a collection of 

 stomachs covering every month in the year, and as nearly as may be all points 

 of the birds' range, becomes more and more trustworthy as it increases in size; in 

 other words, the more stomachs examined the nearer correct will be the result as to 

 the birds' annual diet. The present paper is merely a preliminary report, based on 

 the examination of 679 stomachs of Woodpeckers, and representing only 7 species — 

 all from the eastern United States. These species are the Downy Woodpecker 

 (Dryobatcs piibescens), the Hairy Woodpecker (D. villosus), the Flicker or Golden- 

 winged Woodpecker (Cotopto auratus), the Red-headed Woodpecker (melanerpes 

 trythrucepahlus) , the Red-bellied Woodpecker (Melanerpes caroUnus), the Yellow- 

 beilied Woodpecker (Sphyrapicus vdrivs), and the Great Pileated Woodpecker 

 [Ceoplilneus pileaUis). Examination of their stomachs shows that the percentage 

 of animal food (consisting almost entirely of insects) is greater in the Downy, and 

 grades down through the Hairy, Flicker, Pileated, Redhead, and Yellow-bellied to 

 the Red-bellied, which *akes the smallest quantity of insects. Prof. Samuel Aughey 

 stated that all of these species except the Pileated (which was not present) fed upon 

 locusts or grasshoppers during the devastating incursions of these insects in Nebras- 

 ka. The vegt..;able matter, of course, stands in inverse order. The greatest quantity of 

 mineral matter (sand) is taken by the Flicker, somewhat less by the Redhead, very 

 little by the Downy and Hairy, and none at all by the Yellow-bellied and Pileated. 

 The stomachs of all of the 7 species except the Redhead and Red-bellied contained 

 the substance designated as 'cambium' in the accompanying list of vegetable food. 

 This is the layer of mucilaginous material lying just inside of the bark of trees, and " 

 from which both bark and wood are formed^ It is supposed by many to be the-maln 

 object sought by woodpeckers. Except In the case of a single species the stomach 

 examination does not bear out this view, since cambium, if present at all, v/as in 

 such small quantities as to be of no practical importance. The Yellow-bellied 

 Woodpecker, however, is evidently fond of this substance, for in the stomachs ex- 

 amined it formed 23 per cent, of the whole food of the year. It w^.s found in 37 

 stomachs, most of which were taken in April and October. Of 18 stomachs collected 

 in April, 16 contained cambium, and one of the remaining contained no vegetable 

 food whatever. Moreover, as the true cambium is a soft and easily digested sub- 

 stance It is probable that what is usually found in the stomachs Is only the outer 

 and harder part, which therefore referesentB a much larger quantity. The extent 



