Swifts and hummingbirds are closely related (4), sharing a unique wing structure which allows them to perform intricate acrobatic manoeuvres in the air. Fairly erratic fliers, swifts are also able to turn sharply mid-flight by varying the speed at which they beat their wings (3). The majority of swifts rarely land, except during the breeding season, instead spending most of their lives in mid-air. Swifts forage for invertebrates while in flight, and some species are even able to sleep and mate on the wing (3). In general, swifts are opportunistic feeders and will exploit a variety of food sources, including swarms and even beehives when available (4). Alexander’s swift is a gregarious species, and is typically seen alone, or in small groups containing up to 30 individuals (4).
Very little is known about the specific breeding biology of this species, and it is possible that the timing of breeding may vary slightly throughout the archipelago. On Santiago, breeding is thought to occur in June, from August to September and from January to March, while breeding occurs mainly in August and September on Brava, and in February on São Nicolau (4).
This species primarily nests in fissures and caves in cliffs (4). It is likely that Alexander’s swift constructs a similar shaped nest to other Apus species, typically a simple, shallow cup placed on the floor of the crevice or hole. Feathers, dried grass and other vegetation are used to build the nest, which is loosely stuck together using the bird’s saliva (5). Alexander’s swift lays a clutch of two plain white eggs. As in other swift species, it is likely that both the male and female take turns to incubate the eggs (4).