Little is known of owls in south-western Australia compared with the owls of southern and eastern Australia. Surveys of forest owls in the south-west are almost completely lacking. This study sought to determine the abundance and detectability of owls immediately around the Peel–Harvey Estuary in south-western Australia. The southern boobook (Ninox boobook) and the masked owl (Tyto novaehollandiae) were the only owls detected (n = 23 and n = 1 respectively), although the nocturnal tawny frogmouth (Podargus strigoides) was detected from unelicited calls on three occasions. Southern boobooks were found to be common in this area though they are reported to be in decline in south-eastern and inland Australia. Their detectability was significantly greater in August (late winter) than at other times through unelicited calls; otherwise, there were no detections in winter. A variety of small mammals were detected during the surveys, including: a little red flying-fox (Pteropus scapulatus), a western ringtail possum (Pseudocheirus occidentalis), 19 southern brown bandicoots (Isoodon obesulus), 4 common brushtail possums (Trichosurus vulpecula), 21 rabbits (Oryctolagus cuniculus), a black rat (Rattus rattus), 2 red foxes (Vulpes vulpes) and 22 microbats.