Sick´s Swift

Exhibits a highly specialized morphology adapted to an almost entirely aerial existence, characterized by a streamlined, compact body and a notably short tail with tail feathers that end in stiff, needle-like spines measuring 2 to 6 mm in length. Its body length ranges from 11 to 12 centimeters, with a proportionately large wingspan and an average weight of 14 to 22 grams. The plumage is predominantly a dark grayish-brown on the dorsal region, which transitions to a lighter, pale grayish-brown or ashy hue on the rump and undertail coverts. The throat features a diffuse whitish-gray coloration that contrasts subtly with the smoky gray chest and abdomen. Its wings are extremely long, narrow, and scythe-shaped, engineered for continuous high-speed flight. The bill is extremely short and black, yet it possesses a very wide gape that facilitates the capture of prey mid-air. The eyes are small and dark, protected by dense plumage, and its feet are remarkably short, unsuitable for perching horizontally but equipped with strong claws adapted for clinging vertically to rough surfaces.

Geographical distribution: Displays a wide yet highly seasonal distribution across South America, functioning as a long-distance Neotropical austral migrant. During the breeding season, which corresponds to the southern hemisphere´s summer, it inhabits southeastern and southern Brazil, eastern Paraguay, northeastern Argentina (especially in provinces like Misiones, Corrientes, and Chaco), and northern Uruguay. Following the reproductive period, it embarks on a northward migration to its non-breeding wintering grounds in the Amazon Basin, which encompass northern Brazil, Venezuela, Colombia, Guyana, and occasionally reaching eastern Panama.

Habitat: Occupies an extensive variety of environments due to its strictly aerial habits, although it relies on specific microhabitats for roosting and nesting. It is frequently observed soaring over primary and secondary forests, wooded savannas, forest edges, agricultural lands, and notably, urban and suburban environments with high building density. The availability of artificial chimneys, air shafts, and old masonry structures has allowed it to colonize modern cities, using these human-made features as functional substitutes for its primary natural nesting sites, which consist of hollow tree trunks in mature, dense forests.

Feeding: Is an obligate aerial insectivore that captures its prey exclusively on the wing at various heights within the air column. Its diet consists of a diverse range of flying arthropods, showing a marked preference for small beetles (Coleoptera), flies (Diptera), true bugs (Hemiptera), and especially swarms of social insects during their winged reproductive stages, such as winged ants (Hymenoptera) and termites (Isoptera). To forage, it regularly patrols open expanses or high above the forest canopy, often forming dense feeding flocks or associating with other swift species to exploit thermal updrafts that concentrate insect populations.

Behavior: Characterized by its highly gregarious nature and an active lifestyle spent almost entirely in the air, as it is physiologically incapable of landing horizontally on branches or the ground. Its flight is exceptionally rapid and erratic, marked by brief, twinkling wingbeats punctuated by short, fast glides. During the non-breeding season and migration periods, it aggregates into massive flocks that can number in the thousands. At dusk, these flocks perform spectacular, coordinated spiral descents to enter communal roosts, such as industrial chimneys or vertical shafts, where they cling to the walls supported by their spiny tails.

Nesting: Constructs a distinctive half-saucer nest made of dry twigs securely glued to vertical walls using its own adhesive saliva. The nesting material is collected entirely on the wing by snapping small twigs off branches with its feet or bill. A typical clutch consists of 3 to 5 dull white, elliptical eggs. Both parents share incubation duties equally over a period of 19 to 21 days, as well as the subsequent brooding and feeding of the nestlings with food boluses composed of hundreds of insects packed with saliva. The young fledglings leave the nest around 30 days after hatching, though they continue to return to the nest site to roost for several weeks before becoming fully independent.

Conservation status: Classified globally as Least Concern (LC) on the IUCN Red List of Threatened Species. While the overall population appears stable and the geographic range is vast, the species face potential localized threats from modern architectural developments that seal or eliminate traditional brick chimneys, as well as the widespread use of agricultural pesticides that drastically reduce the biomass of flying insects on which it relies entirely for survival.