Asiatic houbara bustard (recently proposed as a full species, Chlamydotis macqueenii , previously suecies Chlamydotis undulate macqueenii ) is one of the valuable species of arid and semi-arid regions of Iran, which is distance sampling line transect for density estimation in Dasht-e Abbasabad (31500 ha), Where in located in northern part of the Abbas-Abad Wildlife Refuge. Houbara density was estimated at 0.34 individual Km -2 (confidence intervals: 0.21-0.57).Three habitat types were recognized in Dasht-e Abbasabad based on vegetation types including, Artemisia, Artemisia-Zygophylum and Haloxylon. Habitat variables including species richness, total vegetation percent cover, percent cover of dominant bush and shrub species and percent cover of gravel and bare soil were measured using randomly placed 10×10 m plots. Mean vegetation percent cover ± [SD] was 8.6±0.11 for Artemisia, 10.7±0.14 for Artemisia-Zygophylum and 8.6±0.12 for Haloxylon vegetation type. To assess habitat use, plots were located in all of houbara presence points and also pellet index and paired plots were located approximately about 500 m of them. Results of habitat use indicated that houbara pellet density in Artemisia-Zygophylum habitat types was less than Artemisia or Haloxylon, suggesting houbara prefers low vegetation density at fine-scale. In order to better understand species density in the area, raw data collected by Hemami et al. in 2007 were also analysed. These data were collected from 15 plains in Nain, Khour-o-Biyabanak and Ardestan in an area of about 200,000 hectares. The plains were divided into three habitat types based on vegetation types including Artemisia, Artemisia-zygophylum and Haloxylon and houbara density was calculated in each types. Results showed that houbara density in Artemisia was 0.5± (Confidence interval 0.32-0.76), in Artemisia-Zygophylum was 0.47± (Confidence interval 0.32-0.76) and in Haloxylon was 0.26± (Confidence interval 0.15-0.45) individual per Km 2 . Also data of Abbas-Abad in 2007 analyzed separately for comparison with 2009. Results showed that houbara density in 2007 in Abbas-Abad plains was 0.61 ± (Confidence interval 0.36-1.03) individual per Km 2 . Further, group size of houbara decreased from 2.8 in 2007 to 1.68 in 2009. Severe winter in 2008 may have been the main cause of the population decline. Increasing the size of the protected area and increasing the number of the guards especially during the breeding season may also be necessary in order to improve the protection of the species in the region. Keywords: Asian houbara, population estimate, habitat use, Abbas-Abad Wildlife Refuge
