[2] The species are found in Angola, Botswana, the Democratic Republic of the Congo, Kenya, Lesotho, South Africa, Eswatini, and Zambia.

The tail during flight display is expanded vertically into a deep, long keel below the male as he flies with slow wingbeats 0.5 to 2 metres (20 to 78 inches) above his territory.

Because of the seemingly large cost to such male ornaments, the long-tailed widowbird has been the subject of extensive research into the function and evolution of sexually selected traits.

[6] The long-tailed widowbird was described by the French polymath Georges-Louis Leclerc, Comte de Buffon in 1779 in his Histoire Naturelle des Oiseaux from a bird collected in the Cape of Good Hope region of South Africa.

[7] The bird was also illustrated in a hand-coloured plate engraved by François-Nicolas Martinet in the Planches Enluminées D'Histoire Naturelle which was produced under the supervision of Edme-Louis Daubenton to accompany Buffon's text.

[8] Neither the plate caption nor Buffon's description included a scientific name but in 1783 the Dutch naturalist Pieter Boddaert coined the binomial name Emberiza progne in his catalogue of the Planches Enluminées.

[9] The long-tailed widowbird is now one of 17 species placed in the genus Euplectes that was introduced by the English naturalist William Swainson in 1829.

[13] Some researchers have suggested the existence of long-tailed widowbird superspecies based on similarity in male nuptial plumage such as tail length,[3] but this is the topic of some debate.

[15] The southern African population extends from the Eastern Cape (Transkei region) through the Free State, Lesotho, KwaZulu-Natal, and western Eswatini to the Transvaal plateau.

Long-tailed widowbirds are generally found in swampy grassland in flocks consisting of one or two males and a number of females.

Females have a long nesting period and survey these territories and the males that inhabit them prior to mate selection.

[2] Females weave nests, shaped in large dome structures with a lining of seedheads, in the high grass within males' territories.

[2] The nests are placed 0.5–1 meters (19 to 40 inches) off the ground in the upper third of the high grass (Eleusine jaegeri), where the females raise their two to three young.

[2] Charles Darwin first expressed his ideas on sexual selection and mate choice in his book The Descent of Man, and Selection in Relation to Sex in 1871 in response to questions surrounding the elaborate ornamentation that males of some species exhibit despite detrimental costs to survival and seemingly negative consequences for reproductive success.

[18][19][20] It took ninety years after Darwin's initial proposal for the theory to be tested in what has become a classic example of behavioral ecology research.

[6] Their tails, which are often more than half a meter (20 inches) long, are the most extreme sexual ornament among Euplectes and seem to in fact be detrimental to the survival of the male.

[15] Thus, the tail appears to oppose forces of natural selection in the basic sense by decreasing survival in individuals who carry the trait.

[6] Malte Andersson and colleagues tested Darwin's (and Fisher's) theory of female preference for ornamentation as the cause of extreme elongation of the male long-tailed widowbird's tail.

[6] However, this is most likely not the whole explanation, especially considering that prior to mating, females spend a great deal of time comparing males and, thus, do not rely on sighting them from a distance.