190 The Wif.soN Bulletin — No. 89 



each method serves its own end, and that neither can to any 

 extent supplant the other ; that there are at least two big prob- 

 lems in connection with the food of birds : the determination 

 of the specific food, and the amount of food eaten, and each 

 problem demands a different method of solution. 



Laboratory examination of the stomach contents yields at 

 best a list of specific material which chanced to be in the pro- 

 cess of digestion at the time the fledgeling was killed — a list 

 of species which, as W. L. M. states, requires an accomplished 

 entomologist to compile. Given the tarsus of a beetle, it 

 would indeed require an expert systematic entomologist to 

 place that appendage in the proper family, genus and species 

 to which its owner belonged. And with the very many spe- 

 cies of beetles which abound in nearly every habitat, it would 

 probably require a specialist in Coleoptera to perform the 

 task to the satisfaction of the exacting scientific world. In 

 a similar way it would require a specialist in Lepidoptera to 

 ascertain with any degree of certainty the species of moth 

 or butterfly to which a head, a particle of wing, or an isolated 

 leg belonged. The great advantage of stomach examina- 

 tions is the determination of sfrcciHc animals eaten, and unless 

 this is exact, the value of the method as a means of deter- 

 mining the food of the bird is minimized. 



Field observations, on the other hand, should yield data on 

 the amount rather than on the species eaten. It is no difficult 

 matter to watch the feeding of nestlings, whether the neigh- 

 borly warbler and sparrow, or the hawk nesting on the face 

 of a perpendicular cliff. I have sat in a blind four feet from 

 the nest of a Redstart and have watched the actions of the 

 young and parents ; I have removed the Song Sparrows from 

 the nest and had the parents feed them, perched on my fin- 

 ger, within less than a foot of my eyes ; I have sat above the 

 nest of the Duck Hawk and watched the daily life of the 

 birds through powerful binoculars, and identified the birds 

 that were brought in for the young. In every case I feel 

 sure that I could have gathered much data on the amount 

 of food administered to the youngsters had I given my at- 

 tention to that phase of the subject. I think, also, that I 



