The display of the White-winged Nightjar

In 1995, we discovered a population of the poorly known and critically endangered White-winged Nightjar (Caprimulgus candicans) in Yata'i (Butia paraguayensis) palm cerrado at the Mbaracayu Forest Nature Reserve, Paraguay. We provide the first description of the dislay of C. candicans, as observed in December 1995. The display, which appears to function primarily for mate attraction, took place in small arenas and consisted of a regular flight pattern between perches. Noises that accompany the display appear to be mechanical in origin. The modified shape of the outer remiges of male C. candicans suggests a role in the production of this display noise. Male territories were situated exclusively on the upper slopes of ridges in open grassland with a low palm density (termed campo sucio). Territories appeared to be relatively clustered, thus suggesting either a lek-mating system or male aggregation due to the use of specialized habitats as encounter sites for mating. Improved knowledge of the species behavior, breeding systems, and habitat use will facilitate its location at other sites and the development of habitat-based conservation management plans.