Summer habitat selection and abundance of the threatened little bustard in Iberian agricultural landscapes

Abstract

The little bustard Tetrax tetrax is a threatened grassland bird highly reliant on agro-ecosystems for survival. Understanding its habitat requirements throughout its yearly cycle is essential to promoting adequate management practices. A late summer, post-breeding habitat selection study was conducted at three sites located in Alentejo, in the south of Portugal. Overall, 48 flocks were counted. A highly-significant explanatory logistic model demonstrated that little bustard post-breeding sightings primarily occur in locations with greater food availability, adequate vegetation height, and more productive soils. Fallow land and areas grazed by sheep tend to be avoided. Additionally, the species abundance was estimated at 18 sites distributed among the specie’s main range in Portugal, covering 67,000 ha and 971 km of car transects. Another 119 flocks were registered. Surprisingly, hardly any birds were found at priority breeding sites. Overall, the data suggest that important breeding populations of the little bustard dependent upon extensive agriculture within Iberia (generally where soils are less productive), are likely to depend on other areas with greater food availability during the dry summer season. Maintaining suitability of the habitat near important breeding areas with more productive soils could prevent further species movement in search of foraging areas and diminish mortality risk. At these sites, conservation efforts should focus on maintaining the landscape open and ensure the dominance of low intensity land uses with short vegetation, such as cereal stubbles or certain legume crops.