THE VIREOS 



(Family Vireonidae) 



BY A. A. ALLEN, PH.D. 

 ASSISTANT PROFESSOR OF ORNITHOLOGY, CORNELL UNIVERSITY 



MAY is the month of migration. Ever since the last 

 of February the birds have been moving north- 

 ward, but it is not until this month that the flood- 

 tide of bird migration passes over us. The early spring 

 migrants are those that winter but a short distance south 

 of their breeding range and have not far to travel, but the 

 last of April and the first of May bring the birds that 

 have been wintering in Central and South America. Wave 

 after wave of bird life pours upon us; the woods and fields 



A FEARLESS BLUE-HEADED VIREO ON ITS NEST 



All of the vireos are confiding birds and will often allow one to stroke them while 

 on the nest or even take worms from the hand like a pet canary. 



are animated with a new influx of life ; hedgerows and road- 

 sides resound with song and demand our attention. We 

 can step out into the open almost any cloudy evening, when 

 the birds are flying low to escape the moisture-laden clouds, 

 and hear their calls to one another as they wing their way 

 northward under the protection of darkness. Some of 

 them are flying high, others are flying so low that they 

 barely skim the house-tops and a few ill-fated birds, 

 confused by bright lights, dash, themselves to death 

 against tall buildings or become entangled in the meshes 

 of telegraph wires. 



The robins and bluebirds and blackbirds have been on 

 their nesting grounds for nearly two months, many of the 

 sparrows, the hawks, and the woodpeckers, have been 

 common for some time, the ducks have come and gone, 

 and now come the big flights of fly-catchers, warblers, 

 orioles, thrushes, and vireos. 

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The vireos do not come in a body by themselves but 

 usually are mixed in with the flocks of warblers. They do 

 not even come at the same time. The blue-headed vireo 

 which winters in the Southern States is the first to arrive 

 in the North ; then come the warbling and yellow-throated 

 species from Central America, while the red-eyed from 

 South America is last to arrive. 



The vireos are not brightly colored birds, but they wear 

 greens, grays, and yellows in modest, pleasing combina- 

 tions. Although not much larger than their brightly col- 

 ored congeners, the warblers, they move about much more 

 slowly, peering under leaves, examining crevices in the 

 bark, or gleaning about the outer twigs in a thorough- 

 going manner, usually singing as they go. Their larger 

 heads and heavier bills likewise distinguish them. 



With few exceptions the vireos are arboreal birds, fre- 



VIREO BUILDS FLOOR OVER COWBIRD'S EGG 



Nest of a blue-headed vireo showing how a cowbird's egg was kept from hatching 

 by having a floor built over it. The vireos suffer as much as any bird from the 

 parasitism of the cowbird, but sometimes they circumvert disaster in this way. 



quenting the shade trees of the city streets or small groves 

 and wood lots, although they are not out of place even in 

 the dense forests. They are almost entirely insectivorous, 

 and to them, as much as to any other group of birds, is 

 given the protection of the foliage. Leaf miners and leaf 

 rollers, cankerworms, elm leaf beetles, gypsy and brown- 

 tail caterpillars, and even the tent caterpillars are accept- 

 able to them. In their seasons the berries of the elder and 

 mulberry, wild cherries and even the hard blue berries of 

 the Virginia creeper attract the vireos and make a wel- 

 come variation to the usual diet. 



Vireos are great singers. They are singing when they 

 come in the spring, and they continue to sing all summer, 

 even after the exhausting moulting period has caused other 



