TREE SWALLOW 391 



cent green, sometimes with steely blue reflections. Wings and tail deep 

 bottle-green slightly iridescent, the tertiaries broadly tipped with 

 white. Below, pure white slightly smoky gray on the sides." 



The white tips on the tertials are characteristic of the winter plum- 

 ages of both adults and young birds; but these tips wear away before 

 spring. There appears to be no spring molt, but a complete postnup- 

 tial molt begins about the middle of August and is usually completed 

 before the birds go south. This is the only one of our swallows that 

 completes its molt before migrating ; it breeds early, molts early, and 

 migrates late. 



The sexes are much alike, except in the breeding plumage, when 

 the female is duller, the upper parts often being largely dark grayish 

 brown with only the tips of the feathers glossy greenish.] 



Food.—F. E. L. Beal (1918) points out that "in its food habits 

 this species differs somewhat from other American swallows in that 

 it eats an appreciable quantity of vegetable food, frequently filling its 

 stomach completely with berries or seeds." In an examination of 

 343 stomachs, collected in every month of the year over a wide range, 

 Professor Beal found that "the food divided into 80.54 per cent anunal 

 matter to 19.46 per cent vegetable," and he states: "The vegetable 

 food is made up of a few varieties of seeds and berries, but more 

 than nine-tenths of it consists of the fi'uit of a single shrub, the 

 bayberry, or waxberry {Myrica caroUnensis) ^ 



Of the animal food he says beetles make up 14.39 percent, ants 

 6.37 percent, and that Diptera form the largest item of the tree 

 swallow's food (40.54 percent). Minor items are grasshoppers, 

 dragonflies, and spiders. He summarizes his findings thus: "In the 

 food of the tree, or white-bellied, swallow one point is prominent — 

 in its vegetable food it has no relation to man. Every item is wild 

 and of no use. In its insect diet it destroys some parasitic Hymen- 

 optera, some carnivorous Diptera, and a few other useful insects, 

 but this fault it has in common with most other insectivorous birds, 

 and in common with them it is engaged in reducing the great flood 

 of insect life to a lower level. Let it be protected and encouraged." 



When we watch feeding tree swallows we see them chiefly in the 

 role of flycatchers. They tour over meadows, ponds, and rivers, 

 veering from side to side, doubling back with marvelous quickness, 

 snatching up insects as they overtake them or meet them in the air, 

 coursing low down over the meadow grass where flies abound, or, 

 mounting, crisscross through the swarms of higher-flying insects, 

 gorging their throats with the tiny bodies. Ever on the move, they 

 pass back and forth across their feeding grounds, their quick turns 

 evincing success in capture after capture. 



Arthur C. Bent speaks in his notes of seeing a flock of tree swallows 

 alight on a marshy shore and feed from the ground on what ap- 



