Warbling Vireo

The Warbling Vireo is famously plain—grayish-olive above, whitish below, with only a faint pale eyebrow and no wing bars or strong facial markings. What it lacks in appearance it makes up for in voice: its rich, rambling, warbled song is one of the most pleasant and distinctive sounds of summer deciduous woodlands, quite unlike the choppy, repetitive songs of most other vireos.

It favors the leafy canopy of cottonwoods, aspens, and other broadleaf trees, especially along rivers and streams, where it can be maddeningly hard to spot despite singing frequently.

Key field marks

• Plain grayish-olive upperparts, whitish underparts
• Faint pale eyebrow stripe, dark eye
• No wing bars
• Fairly nondescript, thin-billed compared to other vireos

Similar species

• Red-eyed Vireo: bolder head pattern with black-bordered gray crown and red eye.
• Philadelphia Vireo: yellow wash on underparts, especially the throat and breast.
• Tennessee Warbler: thinner bill, more active foraging behavior, different song.

Range and habitat

Warbling Vireo breeds widely across North America, from southern Canada through much of the US, in deciduous woodlands, riparian cottonwood and aspen groves, and suburban shade trees. Two distinct groups occur: an eastern form in broadleaf forest and a western form often tied to riparian corridors and mountain aspen stands.

Migration

A long-distance migrant, wintering mainly in Mexico and Central America.

Behavior

Forages methodically in the canopy, gleaning insects from leaves; often stays hidden in dense foliage, making it easier to hear than see.

Voice

A rich, rambling, warbled song, sometimes remembered with the mnemonic "if I sees you, I will seize you, and I'll squeeze you till you squirt"—delivered in a continuous husky warble unlike the phrase-and-pause pattern of most vireos.

Feeding

Primarily caterpillars and other insects gleaned from foliage in the tree canopy.

Nesting and breeding

Builds a hanging cup nest suspended from a forked twig, usually well up in a deciduous tree. The female incubates 3-5 eggs for about 2 weeks, and both parents feed the young.