Black-throated Blue Warbler

How to find it

Look low. This warbler stays in shrubby understory and the lower canopy. During migration it uses woodlands, parks and gardens, still at lower levels than many warblers.

Check mixed flocks, since vagrants here have joined them. Watch flowers too, such as those of the vine Norantea, where it stops to feed. Birders hope for it during fall migration, and one writer searched a small park in October, peak fall migration. Listen for the flat ctuk call.

How to recognise it

The adult male has a grey-blue crown and back. His face, throat and flanks are black, while the chest and belly are white. That contrast between dark sides and a clean pale front is the quickest way to know him.

Immature males look like adult males but have an olive tint on the back and some white mixed in on the chin.

The female looks quite different. She is grayish olive-brown above, with a narrow pale eyebrow and a pale spot behind the eye. Her underparts are buff-yellow with an olive wash on the chest.

Her best mark is a small white square on the wing, which separates her from other female warblers. Both sexes show a small white patch at the base of the wing feathers. It is large in males and usually shows at least a little in females, though it is not always visible.

What it sounds like

Recording: w_mark_c, CC0 1.0, source, read 4 Nov 2026.

Behaviour and diet

It hunts actively in foliage for small insects, using short flutter flights. It also visits flowers. In Costa Rica it is usually solitary but often joins mixed flocks.

That is worth knowing, because on its wintering grounds it is normally territorial and does not join mixed flocks. Vagrants in Costa Rica have joined them, so a busy flock deserves a careful scan.

It is not especially shy. It often feeds in one small area for minutes at a time, so a quiet walker may get a close look.

Where it lives

In Costa Rica it prefers the forest canopy, forest edges and partly cleared areas on rolling terrain. Known records in the natural history account come from 600 to 1300 m.

Records come from the Caribbean side of the Central Volcanic Range, including Braulio Carrillo National Park and Cariblanco, and from the Coto Brus region near San Vito. Four recent sightings in central Costa Rica were higher, at 1500 to 1850 m, in both forest and farmland with scattered trees.

When to see it

Published Costa Rican records fall between September and March, and the six sight records in one natural history account fall between January and March. One company list also gives an April record, and strays are usually seen in winter.

Similar birds

The female is the one to sort out from other female warblers, and the small white square on her wing is the mark that does it. Check also for the narrow pale eyebrow and the pale spot behind the eye. Her call, a flat ctuk, also differs from the usual warbler chips.

Names and lore in Costa Rica

In Costa Rica the species goes by Reinita Azul y Negro. Other Spanish names recorded for Costa Rica include reinita azul y negra and reinita nigriazul. Mexico and the Caribbean use different names, such as chipe azul y negro.

Status and conservation

The AOCR list marks it as a migrant (M), and in Costa Rica it is a casual to rare migrant and winter visitor, counted among the Caribbean wintering warblers that are vagrants here.

Photography tips

Check every mixed flock, since vagrants in Costa Rica have joined them even though the species normally does not on its wintering grounds. A bird feeding in one small area for minutes at a time gives a quiet photographer a chance. Look for the white wing square on any olive-brown female.