Northern Beardless-Tyrannulet

How to find it

Listen first: the typical song carries far and is a reliable way to locate and identify this otherwise shy bird. If you miss the movement among the branches, its plaintive whistles will give it away. Scan inside bushes and trees, since it hops along branches rather than sitting on open perches. Scrub, thickets, forest edges and watercourses are the places to look, because it is most numerous along watercourses.

How to recognise it

This is a tiny bird, about 10 cm long and 7.5 g.

Head: dark brown, with a small erectile crest and a pale eyebrow stripe.

Bill: pinkish.

Back: grey-green.

Wings: brown, with two whitish wing bars.

Underparts: grey throat, yellowish breast and yellow belly.

Males and females look alike. Among its relatives it is the duller one, especially in the wing bars. Northern birds have paler, greyer wing bars and whitish or pale grey edges on the flight feathers.

What it sounds like

Recording: Grete Pasch, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

It forages more like a vireo or warbler than a flycatcher. It picks insects from bark and leaves with its short, arched bill and seldom catches them in the air.

It usually forages below the canopy and is quiet and unobtrusive for most of the day. It hops between branches and flicks its tail.

When courting or alarmed, it raises its crest, flicks its tail and gives an excited call. In the breeding season males sing a predawn song, and a male may repeat it thirty or more times without a break.

Where it lives

Across its wider range it is fairly common in semi-open dry to semi-humid scrub, thickets, forest edges and secondary forest. It is most numerous along watercourses, and it occurs from sea level to about 2,100 m.

In Costa Rica it reaches only the northwest, the southern end of the species' range. It has also been recorded in the north of the country, in Alajuela province.

Similar birds

In Costa Rica its range overlaps slightly with the Southern Beardless-Tyrannulet, a sister species, and the two do not interbreed there. The Northern is paler and less contrasting, especially in the wing bars. The Southern is called Mosquerito Silbador in Costa Rica and occurs from the Pacific coast southward. The Northern is also easily mistaken for a vireo, warbler or small Empidonax flycatcher, and the high-pitched 'pee' notes are the best way to tell them apart.

Names and lore in Costa Rica

Mosquerito Chillón is the name used in both Costa Rica and Mexico. Other Spanish names include Mosquerito Imberbe, Mosquero Lampiño in Mexico and Mosquiterito Chillón in Nicaragua. The scientific name imberbe comes from Latin for 'beardless', and the genus name Camptostoma comes from Greek words for 'curved' and 'mouth', which refers to the bill.

Status and conservation

The AOCR list marks it as a resident with a possible migrant element (R,M?), and the IUCN lists the species as Least Concern.

Photography tips

One Costa Rica blogger found tyrannulets hard to photograph because most stay in the canopy and rarely sit still. The same blogger shows a Northern Beardless-Tyrannulet growing a new tail. Patience and a good ear for the whistles will help more than hurry.