SPECIES. , 79 



lower end, while a band of 300 goldfinches clung to the ragweed stalks 

 plucking off seeds. If we make the fair assumption that the birds 

 remained on this acre of plenty long enough to obtain a full meal, we 

 can reckon approximately the destruction wrought. At a moderate 

 estimate 20 seeds apiece may be allowed for the goldfinches, 100 for the 

 sparrows, providing that they were from crab-grass or pigeon-grass, 

 and 500 for the doves and bobwhites, or a total of 46,000 seeds destroyed 

 at a single breakfast. 



In the last week of April an attempt was made to ascertain what 

 proportion of the weed seeds ripening on the farm had been consumed 

 during the previous half year. In the wheat field of lot 4, where at 

 the beginning of October there had been scores of seeds on every rag- 

 weed plant, it was difficult to find in a fifteen-minute search half a 

 dozen remaining. In the truck plot of lot 3, which had borne a thick 

 growth of pigeon-grass, examination of an area where there had beeu 

 hundreds of seeds the autumn before would sometimes fail to disclose 

 oTie, and in a mat of crab-grass in the same field frequently not one 

 was left out of a thousand present in October. 



VII.—SPECIES. 



Having discussed under the heads of insects, flesh, fruit, grain, and 

 weed seed the elements that entered into the food of the birds at 

 Marshall Hall, we may now enumerate the birds themselves and indi- 

 cate as far as possible the economic status of each with reference to 

 this particular farm.^* 



WATER BIRDS. 



The data concerning water birds are so limited as almost to preclude 

 anything more than a list of species. 



GREBES. 



The horned grebe [Oolymhus auritus) has been noted on the river 

 at Marshall Hall in December on two occasions. A pied-billed grebe 

 {Podilym'bus podlcejjs) was diving in the bay where the shore curves 

 up to the calamus swamp December 12, 1900 (PI. Ill, fig. 1). During 

 November and December as many as a dozen grebes may often be seen 

 on the Mount Vernon flats, on the Virginia side of the river. Grebes 

 feed much less on fish than is popularly understood, and probably do 

 little harm to fisheries. The large proportion of vegetable matter in 

 their food renders them excellent eating, the flesh resembling that of 

 the adult pigeon in taste. They are difficult to secure, however, as 

 their diving habit protects them from all but the most persistent 

 gunners. 



« Whenever lists ot species of birds are given the figure placed after a nam& 

 indicates the number of stomachs of that species which were examined. 



