Population Status, Habitat Use and Breeding Biology of the Endangered Colombian Horned Lark in an Andean Wetland

Abstract

The Colombian Horned Lark Eremophila alpestris peregrina is an endemic bird of the Colombian Andean Plateau that is endangered due to habitat loss. Information on the population status, habitat use and reproductive biology of this species is therefore vital. We studied these aspects in the La Copa reservoir, where the largest population of this species is found. First, we determined at which locations around the reservoir it was present. At these locations, we used fixed-width transects to estimate its abundance and densities in different habitats for eight months. We monitored its reproductive biology, through behavioural observations and nest tracing during 12 months. The species was only present in plain areas with sparse short vegetation, using grassland, cropland or a mix of the two. Population densities varied significantly between habitats, being high (5.7 birds/ha) in extensive grasslands and medium to low in mixed cropland-grassland (1.1 birds/ha) and cropland (0.41 birds/ha). These differences may be related to the presence of grazing, flooding dynamics, the density of perennial forbs, the size of the grassland fields and the detrimental effect of toxic pesticides used for crop production. We estimated that 133 to 230 (95% CI) individuals (mostly adults), inhabit the entire reservoir. This is a significant number since it may represent 13–23% of the Colombian Horned Lark population. Finally, we present our data on the reproductive cycle of these larks.