Red-eyed Vireo

The Red-eyed Vireo is more often heard than seen as its persistent, if not enthusiastic, song is heard throughout the day. It is one of the most common breeding songbirds in the woodlands of eastern North America. They 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 Western Brazil.

Adult Male (spring/summer)

Crown is blue-gray with a distinct dark border along the upper edge of the white supercilium. A dusky eye-line extends from the lores to behind the eye, where it gradually becomes less prominent. The chin is buffy white, breast, belly white, and flanks and undertail coverts pale yellow. The iris is usually bright red, but some may appear a brownish red. Bill is long with hook at tip. Back, rump, uppertail coverts, and wings and tail olive green. Relatively long-winged.

Adult Female (spring/summer)

Sexes are similar, but the female is typically smaller and lighter than the male.

Juvenile

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.

General:

Large and long-billed Vireo. Length: 12-13cm. Wing: 23-25cm. Weight: 12-26grams.

Behaviour:

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: cherr-o-wit, cheree, sissy-a-wit, tee-oo and continues, averaging one phrase every two seconds. Their call is a nasal mewing: myaah, meeyaen; or a longer, more whining descending: ye-annnnnn when agitated. Red-eyed Vireos may occasionally mimic other species.

Habitat:

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.

Information:

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 fibers. Clutch sizes range from 1-5 dull white with sparse, sepia speckled eggs. The female incubates the eggs and generally spends more time than the male brooding and feeding young.

Similar species:

Black-whiskered Vireo, Philadelphia Vireo, Warbling Vireo, Tennessee Warbler.

Conservation Status:

Listed as Least Concern. However, declines of nearly 75% have occurred in the Western US.

Capture Rates:

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 occurring in July and August as the birds move south to their wintering grounds.

Molt Summary:

PF: HY partial (July – Oct); PB: AHY complete (July – Apr). Molts start on the summer grounds and complete on the winter grounds.

Preformative molt usually includes all gr covs and usually greater alula but no terts or rects.

Adult PB includes a variable amount of wing covs, from none to all, and flight feathers (often just 1-3 terts and the central or other rects. Occasionally other ss and inner pp on the summer grounds. Completing on the winter grounds (Jan – Apr) after suspension in Sept – Dec. Winter molt for ASYs may possibly involve complete replacement of all feathers, including those replaced before migration. This could be considered a PA molt, although this homologous molt does not occur in SYs. More study needed.

PA: Absent (see adult PB for ASYs)

Some intermediates can be difficult to age in spring. Some spring birds show a brownish cast to the iris; may be SYs or possibly ASYs that never acquire full red colour. More study needed.

This HY in August is showing the very dull brown iris diagnostic of first year birds although iris colour can vary from brown to reddish brown in spring and some adults may never acquire fully bright red irises.

The wing of the HY bird above in August is showing very fresh remiges (primaries and secondaries) with no well-marked contrasts between adjacent feathers. The outer primary coverts and alula are narrow and tapered with indistinct to no greenish edging contrasting with the slightly fresher replaced greater coverts.

Ageing warblers and vireos at the end of the summer / early fall requires close scrutiny as molt limits can be difficult to see when hatch year (HY) birds still have very fresh retained juvenal feathers. The wing of this HY bird in September is a good example of this. Under magnification the contrast between replaced lesser, median, greater coverts and carpal covert and retained primary coverts and main alula feathers (A2/A3) can be seen the molt limits indicated with red arrows between the outer greater covert and inner primary covert and greater alula covert (A1) and main lower alula feather (A2). Molt limits like this can be quite subtle with birds in the hand and for this reason, especially after adults of these same species begin to show signs of approaching the end of their complete prebasic molt age should always be confirmed by additional criteria such as skull ossification. Iris colour is also conclusive in this species at this time of the year.

Tail shape can also help being generally more tapered in hatch year birds and more truncate in adults although determining the age of birds by tail feather shape alone is generally not very reliable because of individual variation and the possibility of accidental loss and replacement (i.e., adventitious molt). Tail shape should always therefore be used with caution and only in conjunction with other ageing criteria (e.g. molt limits).

This ASY in July is showing the bright red iris diagnostic of adult (AHY/ASY) birds.

The wing of the ASY in July above is aged after second year (ASY) based on eye colour and lack of any discernible molt limits in the wing and no contrast in wear between the secondaries and tertials; the tertials are usually distinctly more worn due to exposure than the middle secondaries (S4-S6) at this time of the year in SY birds, with a distinct contrast between a worn S7 and fresh S6 (red arrow).
There does appear to be a slight contrast between the greater alula covert and lower main alula feathers which are lacking the same greenish edging and although the outer primary coverts have fairly distinct greenish edging they are very narrow and tapered.

The tail of the same ASY bird in July is showing broad, truncate outer rectrices with a corner to the inner web and very little wear to these feathers.