Yellow-olive Flatbill

How to find it

Listen first, and follow the sound to the bird. Watch the mid-level foliage, and check any mixed flocks passing through. Look for a small, upright bird moving slowly, then making a short sally to snatch an insect. Check the undersides of leaves, because that is where it often takes prey. Flatbills are named for their wide flat bill, which you see best when looking up from below. A bird on an exposed perch gives the best view, and it may move to a new perch if it leaves, so be ready to search again.

How to recognise it

This is a small bird, about 12.5 to 14 cm long and around 15 g. Across its range the back is olive green, the crown grayish, the belly yellowish and the lower mandible pink.

The Central American form, which includes Costa Rican birds, shows these marks:

A light gray crown with no dusky ear mark.

Pale gray cheeks and throat.

A pale yellow belly shading to sulphur yellow.

A whitish to pale yellow eye.

Elsewhere in its range the wings are blackish with two yellowish bars and yellow edges, and a pale line runs from bill to eye with a thin eye-ring. Young birds have paler underparts than adults, a broken eye-ring and a dark eye.

Plumage, eye colour and voice vary a lot across the species' wide range, and some experts suspect more than one species is involved.

What it sounds like

Recording: Zac Peterson, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

It searches foliage slowly and deliberately, then makes short flights of up to about 2 m to grab insects. It often takes prey from the undersides of leaves, and in Costa Rica it sometimes picks at bare branches.

It perches more upright than other flatbills and rarely cocks its tail. Outside the breeding season, adults roost together in old nests, which has been documented in Costa Rica. Nests are hanging pear-shaped bags, often built near an active wasp nest.

Breeding in Costa Rica runs from April to June. Incubation lasts 17 to 18 days, and chicks fledge 22 to 24 days after hatching.

Where it lives

In Costa Rica this flatbill lives on both the Caribbean and Pacific slopes and reaches about 1,400 m elevation. In Mexico the upper limit is lower, near 1,200 m. Its range runs from southern Mexico south into Costa Rica, and on the Pacific side into western Panama.

It works the crowns and the lower and middle levels of forest. In parts of its range where similar flatbills are absent, it also uses tall humid forest.

When to see it

Breeding in Costa Rica runs from April to June, with incubation of 17 to 18 days before chicks fledge 22 to 24 days after hatching.

Similar birds

In Costa Rica it lives alongside two similar flatbills, the Yellow-winged (called Yellow-margined in older lists) and the Gray-headed. Check the pale pink lower bill, the gray crown and the voice to tell them apart.

The Yellow-winged is mainly a Caribbean slope bird, reaching about 600 m in northern Costa Rica and about 1,000 m in the south. It sings a harsh, emphatic series of short notes from a hidden high perch, mostly morning and late afternoon.

Names and lore in Costa Rica

Costa Ricans use the name Piquiplano Azufrado, the same name used in Nicaragua. In Colombia it is Picoplano Azufrado, and in Honduras Cazamoscas Amarillo-oliva. In Mexico it is also called Mosquerito Ojos Blancos or Piquiplano Ojiblanco. The genus name Tolmomyias means bold flycatcher, and sulphurescens refers to its sulphur-yellow tint.

Status and conservation

The official Costa Rican list gives it resident status (R), the IUCN rates it Least Concern, and it is described as common in Costa Rica.

Photography tips

Watch the mid-level foliage and any mixed flocks passing through. A bird sitting on an exposed perch gives the best view, and it may move to a new perch if it leaves. Look up from below to see the wide flat bill.