Red-legged partridge Alectoris rufa productivity in relation to weather, land use, and releases of farm-reared birds

Productivity (offspring production) is a key demographic parameter influencing population dynamics, particularly in r-strategy species, and thus critical for implementing well-based management of populations. Accordingly, the study of factors influencing productivity is useful to develop management strategies in species of conservation concern or subject to exploitation. We studied productivity (covey size and young/adult ratio) of red-legged partridges (Alectoris rufa) in Spain through a large-scale sampling in Andalucia and Castilla-La Mancha, two large areas in central-southern Spain, the core of the distribution of the species. We evaluated potential environmental factors related with productivity that have been considered important in previous local studies (weather, land use, and intensity of releases of farm-reared partridges), using a dataset of 15,357 observations of partridges over three breeding seasons (2010, 2011, and 2012). Average productivity at the end of July was 3 young/adult, indicating 50% chick mortality between hatching and fledging and high breeding failure. We found marked effects of weather, year, and land use on partridge productivity, confirming some previous results at local scale and supporting widespread and simultaneous effects of these factors. We also detected a large-scale negative relationship with farm-bred partridge release intensities, with lower young/adult ratios in areas with high release intensity. This suggests that partridge releases may be contributing to the decline of wild populations. Our results support that correcting the effects of agricultural intensification is the main key to the long-term conservation of the species and suggest that, in dry spring years (leading to low average productivity), many populations could be exposed to overhunting. These results stress the importance of both small- and large-scale adjustments of hunting pressure to partridge productivity, in order to preserve wild populations. Poor hunting bags in “bad” years, along with the increasing demand in the hunting market, may have stimulated the widespread use of releases, further reducing productivity and leading to the current compromised conservation status of wild populations. We discuss some potential solutions to this conflicting situation from the socioeconomic and environmental points of view.