In the Cantareira State Park (São Paulo, Brazil), Southern Bristle-Tyrant has a very low density, with an estimate of only 12.7 individuals per km2 (confidence interval of 7.3-20.2 individuals) (Tonetti 2015, Tonetti et al. 2017). In comparison, the density of a related, globally threatened congener, Restinga Tyranulet Phylloscartes kronei, is 208 [144–272] individuals per km2,) (Gussoni 2014); another Atlantic Forest insectivorous suboscine, Araucaria Tit-Spinetail Leptasthenura setaria has an estimated density of 90 individuals per km2; Cabanne et al. 2007). Based on anecdotal observation, it is believed that most species of Phylloscartes occur in low densities (Goerck 1997).