BIRDS AS CONSERVATORS OF THE FOREST. 263 



lands. The diet of the bird, however, merits some consideration in treating of 

 the good work done by birds in destroying forest enemies. The robin eats a large 

 number of injurious insects, but the ones to which attention is particularly 

 called now are the leaf-destroying caterpillars.' These constitute over eight per cent 

 of the robin's yearly food, as determined by the examination of 330 of their 

 stomachs. They are a very constant element of the diet, and even the birds taken 

 during the winter months had in some way found quite a number of them, probably 

 from crannies where they were hibernating. 



In the summer of 1898, when the forest tent caterpillar overran the maple 

 woods of Vermont, and thereby did much injury to the sugar orchards, thousands 

 of acres were stripped nearly bare of foliage. The insects were of course preyed 

 upon by many birds, but the good work done by one pair of robins deserves to be 

 placed on record. This pair had built their nest upon a maple tree which stood 

 in the corner of a farmer's cowyard, and, like all the other maples in that 

 vicinity, it was covered with caterpillars. The farmer told the writer that every 

 night and morning, as he milked his cows, he watched these robins, which busily 

 fed their young as long as he was there. They did not spend their time going to 

 other trees, but simply took the insects from the outer twigs and leaves, brought 

 them to the nest, and stuffed them into the gaping mouths of the nestlings. 

 This they were always doing at all hours while under observation, until the 

 young were able to leave the nest. 



The good work done by robins in distributing seeds will be detailed on 

 another page. 



The Vireos. 



The vireos are a genus of birds that live largely in the forest, and obtain 

 their food from trees. They are rather quiet and unobtrusive, though active, 

 birds, and their plumage is of modest, subdued colors, with no startling or vivid 

 tints. There are thirteen species and ten subspecies within the boundaries of the 

 United States. They are migratory, so that the good work they do in the northern 

 forests is confined to the summer season. As a rule, they do not frequent the 

 deepest recesses of the forests, but choose the more open and parklike portions. 

 Deciduous trees are also preferred to the evergreens. In foraging they somewhat 

 resemble the orioles in the care with which they examine each leaf for possible 

 caterpillars and other insects. They are birds of tireless industry, and seem 

 always to be engaged in their search for insect food. 



The vireos are practically wholly beneficial to the interests of man in the matter 

 of their food, which consists almost entirely of insects which are for the most 

 part injurious species. Of these the two most prominent items are bugs (Hemiptera) 



