Mouse-colored Tyrannulet

How to find it

Start with the southwest Pacific side, the part of Costa Rica where the northern form lives. Look in open or semi-open country with scrub and pasture rather than in closed forest. Learn the dawn song and the dry, chattering daytime song first, since the voice is often how this bird is noticed. Watch for a small bird in a horizontal posture, and check mistletoe, whose berries it eats a lot of. Confirm the pale eyebrow, two wing bars and pale base of the lower bill before settling on an identification.

How to recognise it

This is a very small, plain tyrannulet, about 12 cm long. Look for these marks:

Grey-brown upperparts.

A pale eyebrow, long and whitish.

Two pale wing bars.

A whitish throat, a greyish olive breast and a pale yellow belly.

A fairly thick bill, with the base of the lower mandible pinkish or flesh coloured.

The tail looks rather long, and the bird often holds a horizontal posture. The pale base of the lower bill, together with the eyebrow and wing bars, helps separate it from lookalikes.

What it sounds like

Recording: Pablo H Capovilla, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

It feeds on insects but also eats a lot of fruit, especially mistletoe berries. It often holds a horizontal posture, and its tail looks rather long. Unlike Southern Beardless Tyrannulet, it does not cock its tail.

Across its range it is mostly resident or makes only local movements, although the southernmost South American populations migrate north in the austral winter.

Where it lives

In Costa Rica it lives in the Pacific lowlands of the southwest. A Costa Rican species page lists it for the San Vito area in Coto Brus, and for the Amistad Pacifico, Pacifico Central and Osa conservation areas.

A specimen is mentioned from 650 m, and the one bird reported there was in open pasture with scrub. Across its range it lives in open to semi-open country that is dry to only moderately humid, mostly below 1000 m.

Similar birds

Its small size and dull colours make it look like several other tyrant flycatchers. Southern Beardless Tyrannulet cocks its tail, which this bird does not. Fuscous Flycatcher and Slender-billed Tyrannulet are also worth comparing. The long whitish eyebrow, two wing bars and pale base to the lower bill help identify it.

Status and conservation

The AOCR list marks it as a resident (R), though Costa Rican accounts describe it as known from very few reports here, even though it is generally common across its wide range.