Measurements
Both Sexes
- Length
- 4.7–5.1 in
12–13 cm - Wingspan
- 8.7 in
22 cm - Weight
- 0.4–0.6 oz
10–16 g
Other Names
- Viréo mélodieux (French)
- Vireo gorjeador (Spanish)
Cool Facts
- The Warbling Vireo may be made up of two or three species. The eastern and western forms differ slightly in size, bill shape, genetics, molt strategies, wintering areas, and possibly voice. Western birds are slightly smaller, have smaller, darker bills, are more olive-green on the upperparts, and have a darker crown than the eastern birds.
Habitat
Open Woodland
Look for Warbling Vireos in mixed-deciduous woodlands, especially along streams, ponds, marshes, and lakes. They are less often found in upland areas away from water. Often associated with clearings and forest edges, the Warbling Vireo sings high in the canopy. Other habitats include urban parks and gardens, orchards, farm fencerows, campgrounds, deciduous patches in pine forests, mixed hardwood forests, and, rarely, pure coniferous forests.
Food
Insects
Forages primarily for insects in the treetops, gleaning them off the leaves. With large prey items (such as caterpillars), the Warbling Vireo whacks its catch against its perch until subdued. They also occasionally eat fruits in the winter when insects are scarce.
Nesting
Nesting Facts
- Clutch Size
- 1–5 eggs
- Number of Broods
- 1-2 broods
- Egg Length
- 0.7–0.8 in
1.7–2.1 cm - Egg Width
- 0.5–0.6 in
1.2–1.5 cm - Incubation Period
- 10–16 days
- Nestling Period
- 11–19 days
- Egg Description
- White, dotted sparingly with reddish, dark brown, or blackish.
- Condition at Hatching
- Helpless, naked with a few tufts of down, eyes closed.
Nest Description
A rough and slightly rounded hanging cup, usually suspended from forks of horizontal twigs. The nest may consist of plant matter, cobwebs, lichen, animal hair, and rarely feathers.
Nest Placement
Tree
The female selects the nest site and may place nesting material in several locations before beginning to build at the final location. The nest is almost always located in the outer portions of a tree or shrub, supported by two lateral branches.
Behavior
Foliage Gleaner
Warbling Vireos can be found singly, in small groups, or in mixed-species flocks in the treetops foraging for insects. Warbling Vireos are also highly territorial; the male usually arrives on breeding grounds before the female and begins singing immediately. Males sing to establish and defend summer territories; they also chase off intruders and patrol territory boundaries.
Conservation
Least Concern
Warbling Vireo populations are stable or increasing over much of their range, although Breeding Bird Survey data show declines in California, Michigan, Ohio, West Virginia, and Wisconsin. Causes of population decline may include nest parasitism by the Brown-headed Cowbird, nest predation, and loss of streamside nesting habitat. Warbling Vireos may be vulnerable to pesticides or herbicide spraying in forests and shade trees. During migration some are killed in collisions with structures such as TV towers. According to NatureServe, breeding populations are of concern in Alabama, Louisiana, and Nova Scotia, Canada.
Credits
- Gardali, T., and G. Ballard. 2000. Warbling Vireo (Vireo gilvus). In The Birds of North America, No. 551 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.