FOOD OF ROBINS AND BLUEBIRDS. 15 



passed uninjured, it follows that birds are the most efficient dis- 

 seminators of these noxious shrubs. This is one evil of which the 

 western robins apparently are guiltless, though the eastern ones eat 

 a few seeds of the poison ivy. 



Among the stomachs examined were those of a few nestlings about 

 half grown. Their food was not found to differ essentially from 

 that of the adults except, perhaps, that the predominance of animal 

 matter was more pronounced, and any great number of stomachs 

 would have shown a considerably higher percentage. One somewhat 

 peculiar feature of the stomach contents was a " wad " of grass or 

 other vegetable fibers in a close tangle and large enough to half fill 

 the stomach. This was found in nearty every stomach of the nes- 

 tlings, and has also occasionally been observed in the stomachs of 

 young of other species. 



/Summary. — While the animal food of the robin includes a rather 

 large percentage of useful beetles, it is not in the consumption of 

 these or any other insect that this bird does harm. A bird whose diet 

 contains so large a percentage of fruit, including so many varieties, 

 may at any time become a pest when its natural food fails and cul- 

 tivated varieties are accessible. While the robin to-day probably 

 is doing much more good than harm, it must be acknowledged that 

 the bird is potentially harmful. In New Jersey it has been protected 

 for years by law and also by public opinion, while the native berry- 

 bearing shrubs have been destroyed and their places filled by do- 

 mestic varieties; consequently the birds have been obliged to resort 

 to cultivated fruits for food, while fruit growers have seen the 

 berry crop, their principal source of income, disappear. It is not 

 probable that individually fruit growers have derived benefit enough 

 from the birds' insectivorous habits to counterbalance the loss suf- 

 fered through their agency. Briefly, the conditions are: Too many 

 birds of a single species and too little of their natural food. Under 

 such circumstances there is no doubt that a law allowing the fruit 

 grower to protect his crop when attacked by birds would be proper. 



In California conditions are somewhat similar though differing in 

 detail. The canyons and hillsides normally suppty robins with 

 their winter food. This, however, sometimes fails, especially since 

 the hill and canyon lands have been cleared to bring them under 

 cultivation as orchards and farms. It is not surprising that robins 

 accept olives as a fair substitute for the Madrona, Heteromeles, and 

 Cascara berries taken from them. Here again is found the very 

 undesirable condition of too many birds of a single species collected 

 in a limited area. They all demand the same kind of food, and 

 when it fails the birds seek till they find an acceptable substitute. 

 It is usually preferable to supply the food they desire, and for which 

 they will amply pay, instead of killing the birds. 



