Species: Red-eyed Vireo
About 10 or 11 subspecies of Red-eyed Vireo are divided into two
groups: North American breeders called
olivaceus group and South American breeders consisting
of resident and migratory populations known as
Red-eyed Vireos migrate long-distances between the breeding grounds
in the U.S. and Canada and the wintering areas in the Amazon basin
of South America. In North America, the Red-eyed Vireo’s
breeding range extends from Southeastern Alaska, Northeastern and
West-central British Columbia south to Northern US. It then
extends across central/Southern Canada and Northern US down through
central and Eastern US. Summering individuals (breeding not
verified) also have been observed in other portions of the western
US from Oregon and Idaho to central Texas and extreme Northeastern
Mexico. In winter they are seen in Northern South America,
including Colombia, Venezuela, Guyana, Suriname, Ecuador, Peru, and
Historically, from 1920s through 1940s, Red-eyed Vireo breeding
range expanded into Oregon, Utah, and Newfoundland. The
planting of trees, particularly eastern species, for shelterbelts
and landscaping may have facilitated this expansion. Today,
these vireos have become most abundant in the eastern as well as the
northern portions of their range.
At a length of 12 to 13 centimetres and a mass ranging from 12 to 26
grams, the Red-eyed Vireo is a fairly large species of vireo.
It has a relatively long bill and a long, flat crown accentuated by
a distinct supercilium. The sexes are weakly dimorphic.
Adults have a blue-gray crown that contrasts with the plain, grayish
olive-green upperparts. The lateral edges of the crown bordering the
upper edge of the supercilium form a distinct blackish border.
The dusky eye-line extends from the lores to behind the eye, where
it gradually becomes less prominent. Adult Red-eyed Vireos have
white underparts with pale yellow flanks and undertail coverts.
Their signature iris is usually bright red, but some adults appear a
slightly brownish red.
Sexes are alike in appearance, but the female is typically smaller
and lighter than the male.
Juveniles are most distinguishable from adults through the fall and
early winter of their first year by their grayish-brown (not red)
iris. As with the adults, undertail coverts are washed with
pale yellow, but the flanks appear washed with olive.
Red-eyed Vireos are similar to Yellow-green Vireos (Vireo flavoviridis) but
their ranges mainly overlap during the winter in South America with
the exception of both species’ rare visits to coastal California
(fall and winter) and the Gulf Coast (spring) and as, in the also
rare case as breeders in the Lower Rio Grande Valley of Texas.
Yellow-green Vireos are bright green above, with yellowish edges to
the wing and tail feathers. They have a bright yellow-green
rump and upper tail-coverts, as well as extensive and brighter
yellow on the underparts. The gray of the crown blends rather
smoothly with the rest of upperparts and has less prominant dark
lateral edges. Comparatively, the Yellow-green Vireo’s
supercilium is very indistinct especially behind the eye or at the
Black-whiskered Vireo (V.
altiloquus) can co-occur with Red-eyed Vireo in coastal
portions of central Florida as well as during migration and summer
along U.S. Gulf Coast as far west as Louisiana. Their main
distinguishing characteristics from Red-eyed Vireos are the blackish
malar stripe, duller green/brownish green upperparts, indistinct
lateral edges of the crown, and a shorter, more abrupt song.
Philadelphia Vireo (V.
philadelphicus) and Warbling Vireo (V.
gilvus), also have plumage patterns similar to that of
Red-eyed Vireo, but they also lack black edging to the crown above
the supercilium. Their foreheads and crowns appear paler, less
bluish, and less strongly patterned than in Red-eyed Vireo.
Additionally, Philadelphia Vireo typically has more yellow on its
underparts and Warbling Vireo has much grayer upperparts.
In North America during the breeding season, Red-eyed Vireos are
mainly insectivorous. They forage from ground level to the
treetops, but activity is usually concentrated in the canopy where
they search small areas for prey while hopping along branches, then
make short flights to new areas. During the nonbreeding
season, Red-eyed Vireo diet consists largely of fruit.
Red-eyed Vireos are more often heard than seen. Their persistent
song consists of simple and whistled phrases:
and continues, averaging one phrase every two seconds. Their
call is a nasal mewing:
or a longer, more whining descending:
when agitated. Red-eyed Vireos may occasionally
mimic other species.
Rangewide, Red-eyed Vireo breeds in deciduous and mixed
deciduous-coniferous forests, but stay away from areas where
understory is lacking. Most often found in riparian areas, they are
more abundant in the forest interior rather than at the edge.
However, Red-eyed Vireos can occur in residential areas, city parks,
and cemeteries where large trees grow.
Red-eyed Vireo males arrive to the breeding grounds and establish
territories, singing from the edges and throughout. Pairs form
soon after the females arrive and selection of the nest site then
begins solely by the female. The nest is open cup constructed
mainly of bark strips, grasses, pine needles, wasp-nest paper,
twigs, and plant fibres. Clutch sizes range from one to five
eggs. The female incubates the eggs and generally spends more
time than the male brooding and feeding young.
Red-eyed Vireo populations are not threatened in any part of their
range and in fact are currently abundant and widespread, showing
increasing population trends in many areas.
There are however, a few
threats that can affect Red-eyed Vireo populations. Like all
vireo species, they are particularly susceptible to cowbird
parasitism both in the chivi (South American) and
(North American) groups. These vireos are also sensitive to
large clear-cuts and forest fragmentation as well as the isolation
of forest fragments. Lastly, Red-eyed vireos are quite
commonly killed during nocturnal migration by colliding with tall
More common in eastern North America, the Red-eyed Vireo
occurs in some areas of the West and although not rare, is
uncommon at the banding station. This vireo is a long
distance migrant as is reflected in the capture rates
(2010-2012; standardized as birds captured per 100 net
hours) occurring in July and August as the birds move south
to their wintering grounds.