Habitat preferences, population size and demographic trends of houbara bustard Chlamydotis undulata in Lanzarote and La Graciosa (Canary Islands)
Published: Volume 53(2), December 2006. Pages 251-269.
Original Title: Preferencias de hábitat, estima y tendencias poblacionales de la avutarda hubara Chlamydotis undulata en Lanzarote y La Graciosa (Islas Canarias)
Aims: To quantify the population size and the distribution patterns of the houbara bustard (Chlamydotis undulata fuertaventurae) in Lanzarote and La Graciosa islands (Canary Islands). To analyze habitat preferences of the species according to topographic, soil, vegetation and human impact variables.
Location: Lanzarote and La Graciosa islands (Canary Islands).
Methods: Bird censuses using the line transect method and the estimation of detection probabilities. Bootstrap to calculate the confidence interval of population size estimations. Classification trees were used to analyze the effect of habitat descriptors on bird species occurrence in 671 0.5 km-transects.
Results: The population size of the houbara bustard was 500 birds (90% confidence interval: 272-801) in Lanzarote and 6 birds (3 - 10) in La Graciosa. The average density in the occupied semiarid environments was 1.63 birds/km2 in Lanzarote and 0.32 birds/km2 in La Graciosa. The maximum ecological density recorded was 3 birds/km2. The most important areas for the species were the steppe plains of Famara- Soo-Zonzamas, Guatiza and Teguise (202 km2), where 85% of the whole population of Lanzarote is included. Slope of the terrain, rock cover on the ground and the density of roads and unpaved tracks had a highly negative influence on the habitat preferences of the houbara bustard. The probability of occurrence of the species increased as the distance to the nearest urban area also increased. Habitat descriptors related to vegetation structure played a minor role in the distribution of the houbara bustard.
Conclusions: According to the data provided by this paper, and those previously published in 1990 decade, the population of houbara bustard in Lanzarote has shown a 40% increase in the last 10-15 years. Only 20% of this population is included in protected areas. The density of the species in Lanzarote is the highest recorded in the whole geographic range of the species in northern Africa and central Asia. Although the species has a favourable protection status in Lanzarote and La Graciosa, conservation efforts should be reinforced in order to preserve semiarid grasslands and shrublands with a steepness of the terrain lower than 15%, a rock cover less than 60%, a low density of roads and tracks (less than 0.5 km/20 ha) and away from urban sprawls (at least further than 650 m).