Available habitat and hence the global population of the Endangered giant nuthatch Sitta magna, restricted to lower montane habitats of south-western China, eastern Myanmar and northern Thailand, remains poorly quantified. Thailand is the only portion of the species’ range for which there is a population estimate. To obtain a more precise estimate of the Thai population and clarify the extent and characteristics of suitable habitat remaining, we conducted 335 point-count surveys at 67 points across eight localities during November 2019–February 2020. We estimated abundance and identified preferred habitat characteristics using N-mixture models, and created suitable habitat maps based on data from surveys and remote sensing. Our estimate for Thailand was 578 (95% CI 391–854) individuals based on a density of 3.7 (95% CI 2.5–5.5) individuals/km2 in 156 km2 of suitable habitat. The giant nuthatch prefers dry forest with a large amount of mature native or planted pine Pinus kesiya and with a large tree basal area and an open canopy. Our estimate of suitable habitat remaining was less than previously reported and thus the population has probably decreased, although most of this habitat is within protected areas. Habitats for the species in Thailand have a stronger level of protection than in Myanmar and China, although habitat in China remains unquantified. We recommend further research in Myanmar and China, which may hold the majority of available habitat for the giant nuthatch. For long-term management, detailed study of the association of the giant nuthatch with pine plantations is required.

The Giant Nuthatch Sitta magna is a globally endangered species presumed to be declining, for which basic parameters of population and habitat associations remain largely unquantified. We focused on Myanmar, which potentially constitutes ~30% of the Giant Nuthatch global range and yet lacks recently published records. Our objectives were to survey key potential Giant Nuthatch localities in, or near, historical locations in Southern Shan State, assess its population status, and quantify habitat associations. Preliminary locality surveys focused on four potential forest patches, assessed by walking approximately 40 km of trails. The species was found in only one of the four localities (Mt. Ashae Myin Anauk Myin [AMAM]), an 18 km2 forest patch in Pindaya and Lawksawk Townships. Here, point counts and vegetation surveys were conducted at 46 locations using an adaptive cluster sampling design. N-mixture models were applied to estimate abundance and identify habitat variables correlated with abundance and detection probability. We also conducted a brief quantitative assessment of tree use and foraging behaviour during one breeding season. Our population estimate for AMAM was 56 individuals (95% CI 25–128) based on a sampled area of 3.25 km2. Abundance was positively associated with larger diameter trees, a higher proportion of pine and oak combined based on their total basal area, and negatively correlated with elevation. Foraging data suggested that Giant Nuthatch preferred to feed on trunks and large branches of larger diameter pines and Fagaceae trees. Based on the estimated population size, AMAM is probably a globally significant locality for Giant Nuthatch and the only confirmed locality in Myanmar since 1992 but is threatened by agricultural expansion. More detailed understanding of the habitat requirements of this endangered species and an assessment of its distribution at the landscape-level, especially in Shan State, would increase the precision of global population estimates.