space use, diurnal movement, and roosting of a variegated ant-pitta (Grallaria varia) in central Amazonia

Abstract

∙ The Variegated Antpitta (Grallaria varia) is the largest member of the terrestrial insectivores guild within its Amazonian range. Despite the bird’s large size and loud vocalizations, however, basic aspects of G. varia’s natural history remain poorly understood. In this study, we conducted intensive tracking of one individual in a nature reserve in the state of Amazonas, Brazil, describing - for the first time with radio telemetry - space use, movement patterns, and roosting sites of G. varia. Over the course of 50 days in July and August 2017, the tracked individual moved slowly through a home range covering ∼ 17.6 ha and was generally quiet, singing at only two of 68 locations that together comprised its home range. Of five roosting sites, four included visual observations where the bird slept 3–7 (mean 4.5) m aboveground in relatively open mid-story trees. We found no evidence of commutes to regular roost sites as all nocturnal locations were located close (mean 59.6 m, range 24–101 m) to the most recent diurnal locations. Slow movements on the ground without commutes to foraging or roosting sites help explain low capture rates in mist nets for this species. Our telemetry data suggest that G. varia home range may be larger than previously estimated in studies that relied heavily on bird vocalizations to determine area needs, though such methods may yield adequate results at times when birds vocalize frequently. Regardless, large area requirements help to explain the disappearance of G. varia documented in tropical forest fragments. © The Neotropical Ornithological Society.