Habitat use and population density of the houbara bustardChlamydotis undulatain Fuerteventura (Canary Islands)

Abstract

Abstract The houbara bustard in the Canary Islands is included into the category ‘Endangered’ on the Spanish Bird Red List according to suspected declines in bird numbers, the loss of previously occupied areas and the suggested endemicity of the taxon. This paper deals with the population size and the distribution pattern of the houbara bustard in Fuerteventura (the largest island occupied by the species in the Canary archipelago, 1730 km2) and analyses its habitat use according to topography, soil, vegetation and human impact variables. We employ distance sampling on 1471 (early spring) and 602 (summer) 500-m transects and measure habitat characteristics within the transects to estimate local densities and population sizes and to test whether the features of the used habitats (as measured in transects where the species was recorded) differed from those available (measured in the whole sample). Topographic and anthropic features are the main determinants of the habitat use of the species, while other descriptors related to vegetation structure and substrate characteristics play a minor role in its habitat preferences. The slope of the terrain is the most important habitat feature constraining the occurrence of the houbara bustard. The proximity of urban areas, the density of paved roads and rural tracks and the extension of agricultural fields also adversely influence its distribution pattern in Fuerteventura. These habitat patterns does not change between summer and early spring considering the whole population of the species (i.e. without considering sexual or age-related differences). Population size is estimated at 177 birds for the whole Fuerteventura island during the breeding season (90% confidence interval: 108–258 birds). Only five areas comprising 247 km2 include 80.8% of the total population in this island, although four of them are not included into the regional network of protected natural sites.