Acadia National Park

Description  ADULT Has olive-gray back and neck. Head has striking pattern of dark gray crown and long, white supercilium, defined above and below by black lines. Note the red iris and rather long bill. Underparts are whitish with dull yellow wash on flanks and undertail. JUVENILE Similar, but with dull iris.

Dimensions  Length: 5 1/2 -6 1/2" (14-17 cm)

Habitat  Common summer visitor (mainly May-Aug) to temperate woodlands across eastern North America. Winters in South America.

Observation Tips  Easy to hear and fairly easy (by vireo standards) to find.

Range  California, New England, Rocky Mountains, Western Canada, Florida, Mid-Atlantic, Eastern Canada, Northwest, Plains, Alaska, Southeast, Texas, Great Lakes, Southwest

Voice  Song is a varied series of 2-, 3-, and 4-syllable phrases, including tse-Oo-ee and tsee-Ooo, sometimes sung in triplets; call is a nasal zz'nrrr.

Discussion  Relatively large and well-marked vireo and the most widespread and familiar of its kind in eastern North America. Forages unobtrusively among foliage and gleans insects while hovering. Easily overlooked if silent, but fortunately it is a vocal species and often attracts attention with its incessant song. Sexes are similar.

Migration Info  During winter, Red-eyed Vireos are most numerous in the northern Amazon basin where they feed primarily on fruits. As the time of migration approaches, they begin to consume more insects. Whether or not a bird crosses the Gulf may be diet-related. Birds with substantial fat reserves are more likely to attempt a crossing; individuals lacking adequate reserves tend to orient northwestward and follow the coast. This species seldom stays for more than a day along the U.S. Gulf coast; most individuals continue their migration at first nightfall. This may be an adaptation that allows Red-eyed Vireos to avoid the intense competition for foraging habitat that is in such short supply in this area. This is one of the more common "eastern" species to appear as a vagrant along the California coast in late May and early June.