Altitudinal distribution, habitat use, and abundance of Grallaria antpittas in the Central Andes of Colombia

Abstract

SummaryGrallaria antpittas are a group of little known birds from the understorey of humid forests of the tropical Andes, with several species having very narrow distributions. At Ucumari Regional Park, which protects the Otún River watershed in the Central Andes of Colombia, five species occur sympatrically at 2,400 m, including the recently rediscovered G. milleri, of which this is the only known population. We studied the patterns of altitudinal distribution, habitat use and abundance of the five species in the park. We found altitudinal segregation at a local scale, with two species, G. ruficapilla and G. squamigera, found at lower elevations (1,800–2,500 m) and two other species, G. nuchalis and G. rufocinerea, at higher elevations (2,400–3,000); G. milleri was recorded only in the 2,400–2,600 m range. The five species overlap in the range 2,400–2,600 m, where they occur in three habitats: early regeneration, overgrown alder plantations and 30-year-old forest. There were no differences in density among habitats for any species; the five species used the three habitats in proportion to their occurrence in the landscape. Grallaria milleri had the highest overall density (1.3 ind/ha) while G. squamigera had the lowest density (0.2 ind/ha), and the other three species were intermediate. We estimated 106 individuals of G. milleri in an area of 63 ha, and only seven individuals of G. squamigera. The Otún River watershed concentrates an unusual number of Grallaria antpittas, including three endemic species, and the information presented here is fundamental to any future habitat management plans to ensure the persistence of these populations.