6 BULLETIN 1249, U. S. DEPARTMENT OF AGRICULTURE. 



tain ash. black alder, honeysuckle, and other shrubs. He also states 



(p. 251)- 



the chief food of the grosbeaks consisted of the seeds of the white ash 

 (Fra-iinus americana) and of the apple, the fruit of the apple and of the 

 American and European mountain ash {Pirns americana and Pints aucuparia) 

 and of the buds of the sugar maple (Acer saccharinum ), and Norway spruce 

 (Abies excelsa). The birds apparently attacked the fruit and buds of other 

 plants only when the supply of their favorite food was exhausted. 



As nearly all the aboye-mentioned items were found in the 

 stomachs examined, the apparent contradictions may be explained 

 by a consideration of the feeding habits of the birds and the locality 

 in which they were observed. In common with the evening gros- 

 beak and the two species of crossbills, the pine grosbeak feeds in 

 flocks which usually settle down in one tree or more and feed for 

 some time, making a full meal on the one variety of fruit or seed if 

 not disturbed. Local conditions, such as relative abundance and 

 availability, probably govern the selection of food. For example, a 

 series of stomachs from Xew Hampshire contained little except seeds 

 of blackberries (Rubus) and the st animate flower buds of pine. 

 TThen both gizzard and gullet were examined it was usual to find 

 the gizzard filled with one of these foods and the gullet with the 

 other. This would indicate that the readily available food supply 

 in the locality was limited to these two items and that the birds in 

 feeding were making a full meal on one or the other. Stomachs of a 

 second series from British Columbia were filled with the seeds of 

 snowberry ( S 'ymphorica rpos) . 



Other similar instances might be cited, each indicating that an 

 examination of the stomachs from either locality alone would result 

 in an incorrect conception of the food of the species. TVith 365 

 stomachs collected from a wide territory for the basis of the discus- 

 sion of the pine grosbeak's winter diet, this difficulty is largely 

 overcome. 



The winter food of the pine grosbeak is almost exclusiyely vege- 

 table. 99.1 per cent of the entire diet being derived from the plant 

 world. In considering the results of the examination of the 365 stom- 

 achs, two items stand out because of their relatiyely high percentages, 

 and the large number of stomachs in which they occurred. These two 

 were Rubus seeds and coniferous buds. The seeds occurred in 207 

 stomachs and amounted to 14.37 per cent of the total winter food. 

 Buds were found in 166 stomachs and made 24.22 per cent of the 

 season's food. Both had been taken from many different regions by 

 birds which were collected in every winter month. Practically all 

 buds were the staminate flower buds of pine, although a few leaf 

 buds and buds of spruce ( () were included in this item. Two hun- 

 dred and seventeen winter stomachs contained one or both of these 

 foods, which together constituted 38.59 per cent of the total con- 

 tents. It is apparent from these data that the fruit of Rubus and 

 buds of conifers are the staple winter food of this species. 



Other items show high percentages, but this is because they con- 

 stitute the entire content of a few stomachs from one locality rather 

 than because there is a general use of the food over an extended 

 area. A conspicuous example of this is the snowberry. which 

 amounted to 17.3 per cent and had been eaten almost exclusively by 

 69 birds from one place. Weed ^eeds formed 7.67 per cent of the 



