BIRDS OF PENNSYLVANIA. 273 



tireless industry do the warblers befriend the human race ; their unconscious zeal 

 plays due part in the nice adjustment of nature's forces, helping to bring about that 

 balance of vegetable and insect life without which agriculture would be in vain. They 

 visit the orchard when the apple and pear, the plum, peach and cherry are in blos- 

 som, seeming to revel carelessly amid the sweet-scented and delicately tinted blos- 

 soms, but never faltering in their good work. They peer into the crevices of the 

 bark, scrutinize each leaf, and explore the very heart of the buds, to detect, drag 

 forth, and destroy those tiny creatures, singly insignificant, collectively a scourge, 

 which prey -upon the hopes of the fruit-grower, and which, if undisturbed, would 

 bring his care to nought." Warblers subsist almost exclusively on insects, such as 

 flies, beetles, spiders, grasshoppers, plant-lice, and various kinds of larvae. 



The Myrtle, Audubon's, Tennessee, Yellow Palm and Pine Warblers, sometimes, 

 though rarely in this region, feed on small fruits, at least it is supposed they do, from * 

 the fact that I have found in the stomachs of each of these species, which were hhot 

 in the fall or winter months, small seeds of fruits. 



GENUS MNIOTILTA VIEILLOT. 

 Mniotilta varia (LiNN.). 



Black and White Warbler ; Black and White Creeper. 



DESCRIPTION (Plate 92). 



Bill rather long ; maxilla very slightly curved ; very short rictal bristles. Black 

 above streaked with white ; below whitish streaked with black or dusky ; two white 

 wing bars ; two pairs outer tail feathers with white spots on inner webs near end. 

 Length about b\ ; extent about 8^ inches. 



Habitat. Eastern United States to the plains, north to Fort Simpson, south in 

 winter, to Central America and the West Indies. 



The Black and White Warbler arrives in Pennsylvania about the last 

 week in April and remains sometimes as late as October 20. Toler- 

 ably common and generally distributed throughout the state during 

 migrations. Breeds quite generally throughout the commonwealth, but 

 in summer is seldom seen anywhere except in the woodland where it 

 rears its young. The nest, usually more or less embedded in the ground, 

 is mostly so carefully hidden by dead leaves that its discovery is fre- 

 quently only made accidentally. Three nests which I have found have 

 all been placed on hillsides in open woods near water. Two of these 

 nests had been visited by Cow-birds, as one contained two foreign eggs, 

 and the other had a young Cow-bird with the young of the warblers. 

 The food of this species consists chiefly of small beetles, spiders, flies, 

 larvae, and Mr. Gentry says, earthworms also constitute a share of its diet. 



GENUS PROTONOTARIA BAIBD. 

 Protonotaria citrea (BODD.). 



Prothonotary Warbler. 



DESCRIPTION. 



The black bill is long (a little shorter than head), sharp and distinctly notched, and 

 without bristles ; wings long and pointed ; tail nearly even. Head and under parts 



18 BIRDS. 



