River Martin - Behaviour

Behaviour

Breeding behaviour is known only for the African River Martin. It nests in large colonies of up to 800 birds from December to April, when the river levels are low. Each pair excavates a 1–2 m (39–79 in) long tunnel in the exposed sandbanks. The pocket at the end of the tunnel has a few twigs and leaves to serve as a nest, onto which two to four unspotted white eggs are laid. It has chasing flight displays and will walk on the ground; it also displays on the ground, but the function of this is uncertain. It rarely perches during the breeding season. Although it has been assumed that the breeding habits of the White-eyed species resemble those of the African species, distinctive differences in foot and toe morphology suggest that it might not use a burrow for nesting.

The African River Martin feeds in flocks over river and forest, often far from water. It eats insects, mainly taking winged ants. The flight is strong and fast, interspersed with glides. Wintering birds regularly perch on treetops, wires and roofs. The White-eyed River Martin feeds on insects, including beetles, which are caught on the wing. Given its size and unusual mouth structure, it may take larger insects than other swallows. This species is described as graceful and buoyant in flight, and, like its African relative, appears reluctant to use perches. This behaviour, together with its unusual toe-shape and the fact that mud was found on the toes of one of the first specimens, suggests that this species may be relatively terrestrial. In winter, it roosts with Barn Swallows in reedbeds. Pamela C. Rasmussen suggested that, given its unusually large eyes, the species might be nocturnal or crepuscular, a factor that could make it highly cryptic and thus partly explain how such a distinctive species remained undetected for so long. Although the fact that the first specimens were supposedly collected roosting at night in reed-beds might be a contraindication, it is possible that the birds might not actually have been caught at the roost; or they might be crepuscular, feeding at dawn and dusk; or they might be capable of both diurnal and nocturnal behaviour, depending on the season or local circumstances.