Mangrove Swallow: where and when to see them

The mangrove swallow is a small, glossy aerial insect hunter of tropical Middle America. Its blue-green upperparts, clean white underside and conspicuous white rump make it particularly attractive in good coastal light. Despite its name, it is not confined to mangroves: rivers, lagoons and other open waters also support it. In Costa Rica, it is associated especially with lowland waterways and wooded wetland edges.

Size

11–13 cm long

Weight

14–20 g

Lifespan

Not reliably established

Status

Least Concern

Mangrove swallows sweep low over water, turning rapidly to catch flying insects and sometimes skimming the surface to drink. They often rest on exposed branches, wires or waterside structures between feeding bouts. Pairs defend nesting cavities, including abandoned woodpecker holes and suitable artificial spaces. Outside immediate nest defense, several birds may feed together where insects concentrate, occasionally mixing with other swallow species above wetlands or rivers. Pairs are monogamous and fiercely territorial around their chosen nest cavity, which they may line with feathers. Outside the breeding season, they often form small, loose flocks, particularly at favored roosting sites in the evening.

• The genus name Tachycineta refers to rapid movement.
• It depends on existing cavities rather than excavating its own nest hole.
• The glossy upperparts change apparent color with the viewing angle.
• It can drink by briefly touching its bill to the water during flight.

Resident birds can occur throughout the year in Costa Rica. December through April generally offers easier travel on the Pacific side and clearer viewing conditions. Caribbean rainfall patterns differ, and local weather and insect activity matter more than a nationwide seasonal rule. While present year-round, peak insect activity during the transition from dry to wet seasons can offer particularly active feeding displays. Local guides can often pinpoint reliable viewing locations based on recent sightings and weather patterns.

Typical habitat combines open feeding airspace with nearby nesting cavities. Mangrove channels, coastal lagoons, estuaries and lowland rivers are important, but freshwater marshes and lakes can also be used. Birds often remain close to water rather than ranging widely over dry uplands. Nesting sites are typically in tree cavities or artificial structures located directly over or very close to water. These swallows are highly dependent on the sheltered, interconnected waterways and abundant insect life found in their namesake mangrove ecosystems.

Flying insects form the diet, including flies, beetles and other small insects caught in flight. Feeding height and flight paths change with insect availability. Swarms above water or along sheltered vegetation edges can attract repeated passes by the same birds. They are aerial insectivores, primarily consuming soft-bodied insects captured during agile flight. Individuals often forage alone or in small groups, exhibiting remarkable maneuverability to snatch prey from the air.

Common name

Mangrove Swallow

Scientific name

Tachycineta albilinea

Animal group

Birds

Size

11–13 cm long

Weight

14–20 g

Lifespan

Not reliably established

Status

Least Concern

Identification

Its white rump and narrow white forehead separate it from the similar tree swallow, which has a dark rump and lacks that pale forehead. Note the glossy blue-green upperparts contrasting sharply with the pure white underparts and bright white rump. Its medium size, often seen alone or in pairs, helps distinguish it from larger swarms of other swallow species.