Die Langsterflap (Euplectes progne) is meestal te sien in oop grasvelde soos die sentrale hoëveld van Suid-Afrika. Hulle kom ook voor in Angola, Kenia, die Demokratiese Republiek van die Kongo en Zambië. In Engels staan die voël bekend as die Long-tailed Widowbird.
Die voël is 16 tot 20 cm lank, die broeiende mannetjie is 60 cm lank, en weeg 25 tot 46 gram. Die mannetjie verkry ‘n kenmerkende swart veredos en lang stert tydens die broeiseisoen. Behalwe die lang stert het die broeiende mannetjie ook rooi skouers en breë swarterige skouers wat met witterige dofgeel begrens is. Die wyfie is groter as ander flapwyfies en die borskant is dofgelerig wit met ligte strepe op die bors en sye.
Die voël is groter as die kortstertflap.
The long-tailed widowbird (Euplectes progne), also known as the “Sakabula,” is a species of bird in the family Ploceidae. The species are found in Angola, Botswana, the Democratic Republic of the Congo, Kenya, Lesotho, South Africa, Swaziland, Zambia, and southern Zaire. The long-tailed widowbird is a medium-sized bird and one of the most common in the territories it inhabits. Adult breeding males are almost entirely black with orange and white shoulders (epaulets), long, wide tails, and a bluish white bill. Females are rather inconspicuous, their feathers streaked tawny and black with pale patches on the chest, breast and back, narrow tail feathers, and horn-color bills.
When flying, male long-tailed widowbirds are readily visible due to their extremely long tails. Between six and eight of their twelve tail feathers are approximately half a metre (approximately 20 inches) long. 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. This research has demonstrated the existence of female choice in sexual selection and indicates the trade-offs between sexual appeal and physical constraints with regard to the evolution of sexual ornaments.