Its scientific name means “dwarf vireo” and truly, at only 10-13 centimeters in length, the flat-billed vireo is one of the smallest birds of Hispaniola, in league with the hummingbirds and todies. This vireo is greyish or greenish-gray with yellow underparts, two white bars on the wings and white-tipped tail feathers. The iris is whitish. The vireos (Vireonidae) whose strong bills characteristically end with a tip in the form of a small hook, is one of the more diverse bird families in the Americas. In the Dominican Republic its name is ciguita Juliana, owing to its resemblance to the black-whiskered vireo (Vireo altiloquus; in Spanish, julián chiví), one of the most common and conspicuous birds on the island. Since its discovery in 1875 on the island of Gonâve, Haiti, this species has puzzled taxonomists.
It is small and active like New World warblers (family Parulidae), but its more robust bill prompted its placement with the Tyrant Flycatchers (family Tyrannidae), alongside the gray kingbird and the stolid flycatcher. The short, flat, wide beak was the source of the confusion, as no other vireo had a similar bill. Later it was reclassified, when it was recognized as a “somewhat peculiar” or “divergent” island species. Its closest relative is the Jamaican vireo (Vireo modestus), which flicks its tail and has a distinctive loud call similar to the flat-billed vireo.
Flat-billed vireos are usually found in lowland dry forests and scrub-shrub habitat, often at the base of limestone hills. They move actively through vegetation near the ground, where they feed on fruits and insects, some of which they catch on the wing. As with other insectivorous birds, they have specialized feathers at the base of their bills that resemble a mammal’s whiskers. These feathers may allow them to better sense and capture its prey. Their call is a repetitive and high pitch uit-uit-uit-uit-uit-uit that slows down as the day progresses. Early in the morning, the call is fast, slowing by 8:00 am, and slower still by 10:00 am.
“What squeaks it gave by opening his wide beak! But what a fragile body!” Anabelle Stockton de Dod
Flat-billed vireos often are seen in pairs, with the sexes responding to each other’s calls through the vegetation. Males aggressively defend their territories. Their deep, cup-shaped nest hangs from a small branch, as is typical of vireos. The nest is lined with grasses and sometimes adorned with tree bark and insect silk. In it, the female lays 3 to 5 white eggs. Unlike its relative the black-whiskered vireo, the flat-billed vireo is uncommon throughout Hispaniola, but still common enough to avoid the endangered species lists. Although it had a widespread historical distribution on the island, its current distribution is unclear in many areas in the wake of human occupation and habitat change that has occurred. More studies are needed to reveal its true status.