[4] The cliff swallow's average body length is 13 cm (5.1 in), and they have short legs and small bills with relatively long pointed wings.

[4] In addition, during incubation females will lose feathers on their lower breast to create a warm patch for sitting on their eggs.

[2][4][8] The juvenile cliff swallows' white forehead and throat markings have high variance between unrelated individuals compared with those from the same clutch.

[9] The family that encompasses approximately 90 species of swallows and martins, Hirundinidae, includes birds that have small stream-lined bodies made for great agility and rapid flight.

[6][13] The majority of nesting colonies are situated in close proximity to fields, ponds, and other ecosystems that would hold a large variety of flying insect populations to sustain their energy requirements during the breeding season.

[2][4] The cliff swallows' wintering grounds have been recorded as South American countries, such as Southern Brazil, Uruguay, and parts of Argentina.

Cliff swallows live in a colonial lifestyle during the breeding season, composed of a large number of pairs per nesting site.

[2][4][5] This group-style life can present the birds with some benefits and disadvantages; valuable information can be shared through group learning about food location and habitat preferences, but it is also much easier to transmit parasites or diseases when living in close proximity.

[2][4] These birds are day-hunters (diurnal), returning to their nesting sites at dusk, and are not very active during cold or rainy weather because of the low number of prey available.

[2][4] When the swallows return to the nesting site at dusk, they often fly in a tightly coordinated flock overhead, in such close synchronization that they may appear as one large organism.

[5] The cliff swallows' social behavior does not end with these "synchronized flying" displays; they use special vocalizations to advise other colony members of a good prey location where ample food is available.

[2] Juvenile cliff swallows are said to have established a unique call by the approximate age of 15 days, which allows the parents to identify their chick from others in the colony.

[2][4] The "squeak" call is of great interest to researchers because this is the special vocalisation made at a distance from the colony when a bird encounters a good foraging area.

[2][4] The cliff swallows have been observed to skip from one to five years between breeding at the same place to avoid parasite infestations, but some pairs will return annually to the same site.

[2][4] Older birds are usually found in smaller colonies and exhibit earlier nesting times, avoiding the parasite manifestation that comes with the hot mid-summer season.

[4][16] Further, taking the extra time to build a nest from scratch will mean reproducing later which could negatively affect their chicks' survival.

[2][17] The "victims" of brood-parasitism must nurture more chicks with higher energy costs and decreased fitness because they are raising young that will not pass on their own genetic material.

[17] The male cliff swallows will also take part in this gene-spread by mating with more than just one female, contributing to genetic variation throughout the colony.