BIRDS IN RELATION TO AGRICULTURE 169 



our forest and shade-trees. The vireos also are unrivalled 

 as destroyers of insects which feed on the foliage of trees. 



The swallows and martins scour the air in the search of 

 adult insects of all forms, which make up their entire diet. 



Our native sparrows, in which group we do not include 

 the undesirable aUen house-sparrow, are among the greatest 

 weed-destroying agencies, owing to their appetite for weed 

 seeds. The song-sparrow is one of our most welcome spring 

 arrivals. About three-fourths of its food consists of weed 

 seeds and one-fourth of insects. Beetles, especially weevils, 

 form the greater portion of the insect food. The chipping 

 sparrow, whose confiding ways give it a warm place in our 

 affection, is the most insectivorous of our sparrows. About 

 42 per cent of its food consists of insects and spiders, and 

 caterpillars make up the major portion of the insect food, 

 especially when the young are being reared, when as many 

 as seventeen feedings per hour, on an average, for a brood 

 of four nestlings, have been recorded. The retiring and 

 sombre junco or snowbird destroys insects and feeds on 

 weed seeds. An examination of 500 stomachs gave 23 per 

 cent animal food (caterpillars, bugs, and beetles), and 77 

 per cent vegetable food, of which over 61 per cent consisted 

 of weed seeds. In September the proportion of weed seeds 

 may rise as high as 95 per cent of the food. 



Among the commoner weed seeds consumed by the spar- 

 rows we find the seeds of bindweed, lamb's-quarters, rag- 

 weed, amaranth, pigeon-grass, etc. Judd records the re- 

 sult of the examination of over 4,000 stomachs of twenty 

 species of sparrows. It was found that for the entire year 

 weed seeds form more than half their food, and during the 

 colder months of the year these seeds constitute about four- 

 fifths of the food of many species. A single bird will often 

 be found to have eaten 300 seeds of pigeon-grass, or 500 

 seeds of lamb's-quarters or pigweed. Beal estimated that 

 the tree-sparrow may consume one-quarter ounce of weed 



