Southern Beardless-Tyrannulet

How to find it

Start on the Pacific side and go out early. Bird counts in a San José park ran from 5:40 to 9:40 a.m., the time of greatest bird activity, a good window for small birds like this one. Listen first for the simple whistles, then look for a small, active bird with a cocked tail working through foliage. Watch for a raised crest when it calls. It also answers recordings of the local pygmy owl, coming close and fussing, and birders use this to bring it into view.

How to recognise it

This is a tiny flycatcher, about 10 cm long and 7 to 9 g.

Field marks, in plain terms:

- Back: dull olive.

- Head: pale grey crest, whitish eyebrow, narrow white eye ring.

- Bill: short, with an orange base.

- Underparts: grey throat, yellowish breast, yellow belly.

- Wings: brown with two pale wing bars.

- Tail: often held cocked.

A Costa Rica guide advises ignoring the name and checking the shortish bill with a pale base, a hint of a crest and the two wing bars. That helps avoid mistaking it for a small warbler. It can also look like a tiny Yellow-bellied Elaenia, so size and the short bill matter.

What it sounds like

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

Behaviour and diet

This is an active bird that feeds like a vireo or warbler rather than sitting upright on a perch. It catches insects in flight and also picks them off leaves and twigs. Its food is insects, spiders and berries, including mistletoe berries.

It often raises its crest while calling. The nest is a hanging dome with a side entrance, usually placed near a wasp nest, which probably helps guard it from predators.

Where it lives

In Costa Rica the bird is the Pacific slope form flaviventre, found on the Pacific coast and in the southwest, and it continues into Panama, where it lives on both coasts. Here it reaches about 1,200 m, so it is mainly a lowland and foothill bird. Across its whole range it is found from sea level up to about 2,800 m. It is not expected in the Central Valley, though one was logged in La Sabana park in San José.

When to see it

It stays in the area all year, since it is a resident across nearly all of its range. In Central America it breeds between December and March.

Similar birds

The Northern Beardless-Tyrannulet looks much the same but has paler, less contrasting plumage, while the southern bird always looks brighter, especially in its wing bars. The two overlap in central Costa Rica without interbreeding, and were once treated as a single species. The Northern reaches only the northwest of the country. The Southern's whistles also set it apart from the Slender-billed Tyrannulet, whose song is a level, rapid trill.

Names and lore in Costa Rica

Costa Ricans call it Mosquerito Silbador, the same Spanish name used in Peru. Colombia uses Tiranuelo Silbador and Venezuela Atrapamoscas Lampiño. The Northern Beardless-Tyrannulet is Mosquerito Chillón in Costa Rica, and 'chillón' means shrill, so the two species carry different names.

Status and conservation

The AOCR list marks it as a resident (R), and the IUCN lists it as Least Concern because its range is huge.

Photography tips

Listen for the whistles and look for the raised crest while it calls. Recordings of the local pygmy owl bring it close, where it fusses in view. Go early, in the hours of greatest bird activity.