Mangrove Swallow

How to find it

Look near low-lying water and mangroves. The species often perches between flights, so scan waterside perches such as stumps and wires. Watch too for birds skimming low over the surface. Stay near sea level, since it is rarely seen in the highlands. Calm, wide water is the best bet: lakes, rivers, estuaries, salt pans and sometimes flooded pastures. Outside the breeding season, look for small flocks gliding over water.

How to recognise it

Adults have shiny blue-green upperparts and white underparts. The tail and flight feathers are blackish. It is a small swallow, about 13 cm long.

The mark to look for is a thin white line above the eye, in front of it. Only two other Tachycineta swallows share this mark, Violet-green and White-rumped.

A local Guanacaste bird guide calls it the green-and-white Mangrove Swallow and uses it as a size comparison: the Gray-breasted Martin, a large gray swallow with a whitish belly, is much bigger. In Costa Rica the Mangrove Swallow is also smaller and darker on the back than the Tree Swallow.

Behaviour and diet

It flies low and fairly straight over the water, feeding mainly on insects, including large ones such as dragonflies and bees. In the breeding season it is very aggressive toward other swallows and martins, so nests are spaced several hundred metres apart. When breeding it is usually alone or in pairs.

Outside the breeding season it is social. Flocks of up to 50 gather where low perches such as stumps and wires stand near water, and small flocks glide over the surface on rapid wingbeats.

Where it lives

It lives mainly in coastal areas, near low-lying water and mangroves. In Costa Rica it usually lives from sea level to about 500 m. It has been found as high as 1,000 m, but it is rarely seen in the highlands.

A Costa Rican field-guide entry says birds favor wide, calm open water such as lakes, rivers, estuaries, salt pans and sometimes flooded pastures. It is a non-migratory species.

When to see it

A Costa Rican natural history text says the birds breed from March to April, with a loose cup nest in a crevice or stump hole over or beside water, often under 2 m high, holding 3 to 5 white eggs.

Similar birds

The Tree Swallow is the main look-alike. It is larger than the Mangrove Swallow and lacks the white rump. Both have a glossy green or blue back and white underparts, but the thin white line in front of the eye separates the Mangrove Swallow. The Tree Swallow is a migrant in Costa Rica.

Names and lore in Costa Rica

Costa Rica's official Spanish name is Golondrina Lomiblanca, which means white-backed swallow. It is also called golondrina de manglar and golondrina manglera.

Status and conservation

The official Costa Rican list (AOCR) marks the Mangrove Swallow as a resident (R), and the IUCN lists it as Least Concern.

Photography tips

Waterside stumps and wires are where flocks gather outside the breeding season, so a low perch near calm water is a good place to wait for a closer look.