FOOD OF NESTLING BLACKHEADS. 75 



at this age, beetles composing three -fourths of the whole diet, and 

 over 23 percent was contributed by the flower-beetle alone. Black 

 olive scales are most important among the remaining elements, 12 

 percent being composed of these pests. Hymenoptera, caterpillars, 

 spiders, and insect eggs also were taken, and each of the members of 

 one brood had a few bits of eggshell in its stomach. 



Caterpillars again enter into the diet of the two-weeks old fledge- 

 lings, composing 45 percent of the whole amount, 21 percent being 

 cankerworms. Black olive scales are 7 percent, and beetles, includ- 

 ing lamellicorns, ground and click beetles, compose 26 percent of the 

 food, the remaining animal elements being Hymenoptera and snails. 

 The vegetable matter, 13.3 percent of the whole food, consists of cher- 

 ries, strawberries, blackberries, bits of wheat, a few seeds, and spires 

 and wads of grass, which last-named articles curiously enough are 

 found in the stomachs of many other nestling birds. 



The oldest fledgelings thus approximate more nearly in diet to that 

 of the adults, even partaking of their fruit-eating habits. It is evi- 

 dent also, from the study of nestling blackheads, that vegetable mat- 

 ter is fed in gradually increasing quantities, corresponding, probably, 

 either as cause or effect, to the growing muscular development of the 

 stomach. Some grosbeaks observed by Professor Beal fed their nest- 

 lings only two to five times per hour, but as the feeding was accom- 

 plished by regurgitation it is probable that the stomachs of the young 

 were practically filled during every visit to the nest. 



Reviewing, it has been noted above that the nestlings of the black- 

 headed grosbeak are fed a great number of codling moth pupa?, cank- 

 erworms, flower-beetles, and black olive scales, the destruction of 

 which is greatly to the advantage of agriculture. When very young 

 their food is entirely animal, and consists in great part of these 

 grievous insect pests. 



Summary. 



Examination of 226 stomachs of the black-headed grosbeak, the 

 majority of which were collected in California, shows that during six 

 months' stay in its summer home the bird consumes on the average 

 34.15 percent of vegetable and 65.85 percent of animal food. 



Reports that the bird damages cultivated fruit are fully sustained 

 by stomach examinations, figs and cherries appearing to be the kinds 

 most injured. From 10 to 15 per cent of the food consists of culti- 

 vated fruits;- a slightly smaller amount is weed seed, while the pro- 

 portion of grain devoured is trifling. 



It has been brought out that small orchards may be economically 

 protected by means of bird netting. Large orchards may be pro- 



