BIRD GUARDIANS OF THE TREES 



By Edward Howe Forbush 



Massachusetts State Ornithologist 



TN studying the economic relations of birds to man and 

 -*- other forms of life, this question is most important: 

 What do birds do in the world? As we investigate their 

 activities from our viewpoint, we find few birds alto- 

 gether useful to man. Many are harmless and some 

 harmful, but the vast majority of birds which come in 

 close contact with man and his property benefit him far 

 more than they injure him. In primeval nature all birds 

 are beneficial. 



The well-being of each form of life depends more or 

 less on the welfare of other organisms. Take the rela- 

 tions of the bird and the tree. In the battle of life birds 

 and trees are interdependent. Trees furnish buds, blos- 

 soms, fruit and seeds which birds use for food. Trees sup- 



a single tree sometimes run into hundreds, and the indi- 

 viduals of each species if unchecked would soon number 

 untold millions. Before such countless hordes man 

 would be powerless. We can spray orchards and shade 

 trees with poisonous insecticides, but we would stand 

 aghast at the impossible task of spraying all the trees 

 in all the woods. We must perforce depend on the natu- 

 ral enemies of insects to protect our forests. Fortunately, 

 birds and other foes of insects, wherever their numbers 

 are sufficient, act as effective forest guardians. 



Professor F. E. L. Beal, whose experience in studying 

 the food of birds was greater than that of any man 

 now living, believed that birds were an effective check 

 upon the increase of insects, and that it was doubtful 



Photograph by Cordelia J. Stanwood. 



CHICKADEES JUST FROM THE NEST 



rhey destroy spruce moths and many other forest pests. These youngsters appear to be deliberately posing for an effective 



picture. 



port many insects that are eaten by birds ; also, they pro- 

 vide birds with hiding places in hollow trunk and limb, 

 excellent nesting places and leafy shelter from sun and 

 storm. Birds, on their part, protect trees by eating 

 the surplus insect enemies of trees, thus preventing un- 

 due increase of these enemies. Humming birds like bees 

 fertilize tree blossoms, and many birds distribute and 

 plant tree seeds. Bartram believed that Jays alone would 

 soon replant all cleared lands were it not for the imple- 

 ments of soil cultivation. 



The possibilities of the increase of forest insects are so 

 appalling that potent forces to keep them within bounds 

 are indispensable ; otherwise, insects might destroy all 

 forest trees. The numbers of insect species that attack 



if anywhere else in the animal kingdom "any other re- 

 straining influence so important" could be found. 



The normal reaction of birds upon the insect enemies 

 of trees is that of annual and perennial repression. All 

 through the winter months our forests are searched, tree 

 after tree, by Nuthatches, Titmouses, Creepers, Kinglets 

 and Woodpeckers for eggs and other hibernating forms 

 of insects. As spring advances, as buds open, as tiny 

 caterpillars and grubs emerge from the egg, come the 

 hosts of arboreal birds Sparrows, Thrushes, Warblers 

 and others sweeping through the woods in migration. 

 Under normal conditions they destroy something like 

 ninety per cent of the tiny caterpillars hatching upon the 

 external parts of trees before these caterpillars become 



