The Long-tailed Ground-roller (Uratelornis chimaera) is a globally Vulnerable, restricted-range species of dry forests in south-west Madagascar. We studied a population in 1997–2000, finding that nest-building was relatively synchronous and that pairs preferentially nested next to open areas, such as driveable tracks. By searching for trackside nests and for footprints, we conducted surveys throughout the known range of the species. Total transect coverage was 153 km, along which we encountered a minimum of 28 breeding pairs. By dividing the transects into 41 randomly distributed survey strips, each 1.2 km in length and 200 m broad, we intensively sampled an area of 9.84 km2. Using transect data, we made a tentative estimate of 5.7 mature adults km−2, from which we estimated a global population of 21,092 individuals, based on our calculation from satellite imagery that 3,706 km2 of suitable habitat remained. By comparing habitat data at points with and without ground-rollers we found that, contrary to previous statements, they prefer lower stature or degraded habitats, and have no direct association with the endemic cactus-like tree Didierea madagascariensis. We used a novel census technique to provide the first quantitative data on population size, population density, breeding behaviour and ecology in the Long-tailed Ground-roller, or any member of the family Brachypteraciidae, information that is crucial to the design of effective conservation programmes.