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Philadelphia Vireo

(Vireo philadelphicus)
Banded September 18, 1998 - Carmel, Indiana

General Information

The Vireos occur only in the western hemisphere. Of the 52 or so species resident to the Neotropical region of Central and South America, only 13 or so migrate to North America to breed and raise their young.

Among these is the Philadelphia Vireo, first observed near Philadelphia in September 1842 by John Cassin, one of America's foremost ornithologists. Its name is a bit misleading as this species is a migrant regularly seen in the USA as it makes its way to and from its breeding grounds in the woodlands of Canada and the extreme northern USA.

The Philadelphia Vireo is 4.5 to 5 inches, long with a wingspan of 8 to 9 inches, and weighs from 12 to 16 grams. It lacks wing bars, is similar to the Warbling Vireo, but usually shows a strong yellowish wash across the under parts. The back is grayish with an olive green wash.

Figure 1- Philadelphia Vireo

Figure 2 - Philadelphia Vireo

The stout bill and solid body distinguish the Philadelphia Vireo from the slimmer, thinner billed Tennessee Warbler. Philadelphia Vireos are generally quiet during migration, and so are often overlooked.

The grayish head and face show a white eyebrow stripe, dark lores and dark eyeline. The amount of yellow on the underside varies, but the brightest yellow occurs on the throat and breast.

Figure 3 - Philadelphia Vireo

Figure 4 -  Undertail Coverts - Philadelphia Vireo

From underneath, the yellow undertail coverts distinguish this species from the similar Tennessee Warbler that has white undertail coverts.

Vireos have ten primary flight feathers. In the Philadelphia Vireo, the tenth primary is reduced or vestigial.

Figure 5 - Primary Flight Feathers

Figure 6 - Upper Wing Coverts

The darker primary coverts of this individual contrast with the lighter color of the greater coverts, indicating that this is a young bird.

The breast, flanks and undertail coverts are yellow, but the stomach shows white. The amount of yellow will vary between individual birds.

Figure 7 - Underwing and Flanks

Figure 8 - Upper Tail

The tail is also dark with an olive wash to the edges and upper tail coverts. The pointed tail feathers of this individual indicate it is a first year bird.

Nesting Behavior

The Philadelphia Vireo nests in the woodlands of Canada and the extreme northern USA. A cup nest of twigs, fibers, spider webs and grasses is built in scrub or secondary growth area near water. The nest is placed in a deciduous tree from 10 to 40 feet high. From 3 - 5 eggs, incubated by both sexes, hatch in about two weeks. Both parents tend the young, who leave the nest in about two weeks. The young birds usually stay with the parents for a few weeks prior to heading south to their wintering grounds.

Banding Recoveries

The Bird Banding Lab web site reports that between 1955 and 1997, a total of 18,658 Philadelphia Vireos were banded. Of these, only 7 have ever been recovered, a very low recovery rate of 0.037%.

Banding studies show that the Philadelphia Vireos are short to long distance migrants that winter in Central America and northern South America.

If you should recover a banded bird, please report the band number to the Bird Banding Lab by calling
1-800-327-BAND.

Economic Importance
and Conservation Status

Philadelphia Vireos, like other vireo species, are important predators on insect pests, especially caterpillars. They also consume fruits such as bayberries, rose hips, and wild grapes, dispersing the undigested seeds into new areas.

Monitoring data show that populations are holding steady. This probably reflects the good health of their woodland breeding habitats across Canada and the extreme northern USA.

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