BIRDS IN" RELATION TO THE ALFALFA WEEVIL. 45 



month, when the rigors of winter have reduced the insect to its lowest 

 ebb ; and any agency in the work of destruction that can be brought 

 to bear at this time is of the utmost importance. The food of the 

 robin in Utah speaks highly in its favor. Some complaint was heard 

 that it injures cherries, but this trait does not seem sufficiently uni- 

 form to offset the good it does. Until the weevil is reduced in num- 

 bers the services of the robin as a destroyer of breeding adults alone 

 ought to earn for it the utmost protection. 



MOUNTAIN BLUEBIRD. 



(Sialia currucoides.) 



The mountain bluebird is an abundant breeder throughout the 

 higher altitudes of Utah and in spring and fall is a migrant in the 

 irrigated valleys. In the spring flocks of 5 to 15 often may be seen 

 in the vicinity of infested fields. In their search for food, usually 

 confined to the borders of fields and along roadsides where fences and 

 telephone poles afford favorite perches, the bluebirds come in contact 

 with hibernating- or recently emerged adult alfalfa weevils. A con- 

 siderable number of bluebirds were encountered in April in the Salt 

 Lake Valley, and in July they were found in post-breeding flocks in 

 alfalfa fields in the Weber Valley. At the latter place the fully 

 fledged young were feeding extensively on the larva?, which were then 

 present in great numbers. 



Of seven birds collected in April five had fed on breeding weevils. 

 In bulk the weevils composed over 4 per cent of the food and were 

 taken at an average of about two and one-half per bird. Twelve 

 was the highest number recorded for any individual. 



The major portion of other animal food at this time of year con- 

 sisted of caterpillars (32.5 per cent) and ground beetles (31.3 per 

 cent). In one stomach eight cutworms formed about four-fifths of 

 the food and in another a similar number composed over 72 per cent. 

 Among the ground beetles the genus Amara predominated. Crickets 

 appeared prominently in two, and in one a large number of dung 

 beetles (Aphodius) formed about two-thirds of the food. 



Each of the nine birds collected during July had fed on the insect, 

 which amounted to 11 per cent of the food. One, a juvenile bird, 

 had eaten at least TO of the larvae, forming 40 per cent of its food ; 

 another, 17 larvae and 5 adults; and a third about 12 larvae and 3 

 adults. 



The remaining animal food of the bluebirds at this time was char- 

 acterized by a large proportion of hemipterous remains made up 

 largely of the small cicada (Platypedia putnami) , so abundant among 

 the oak chaparral of the foothills. 



The mountain bluebirds, like many other spring and fall migrants, 

 render their most valuable services as weevil destroyers in early 

 spring. More extensive investigations of their general food habits 



