Parameters determining population dynamics of red-legged partridge (Alectoris rufa): a simulation approach

Resumen del trabajo presentado al XXXth International Union of Game Biologists and Perdix XIII, celebrados en Barcelona (España) del 5 al 9 de septiembre de 2011.Red-legged partridge (Alectoris rufa) populations in the Iberian Peninsula are declining in the last decades, but monitoring data are obscured by the effect of generalized releases for game purposes. Therefore, identifying the main demographic parameters affecting partridge population dynamics is required in areas free of releases. One of these regions is Navarra (northern Spain), where the species also shows a clear declining trend during the last 20 years. During a field work carried out in 6 areas of Navarra (5.500-7.000 Ha) between 2006 and 2009 (February-November), involving the radio-tracking of 139 adult partridges and 110 chicks, we estimated demographic parameters such as adult and chick survival, hunting mortality, and several reproductive parameters. In order to identify the parameters most affecting population dynamics, we developed different individual-based population models using Program Netlogo. Models were calibrated using data of population trends and chick/adult ratios from independent temporal series (spanning 1990-2010). Results from a sensitivity analysis of the demographic parameters show that the population was most sensitive to survival of pre-reproductive and nesting adults and survival of chicks between one and five months old, which produce larger changes in lambda with small changes in the parameters. However, if only one parameter should be manipulated to achieve population recovery (lambda >1), either nest success or survival of chicks younger than one month should be improved. In a more realistic scenario, habitat management will improve simultaneously different parameters which would have larger effects on lambda. Parameters highly susceptible of improvement, due to their low estimated values in the field, are adult survival, nest success, and chick survival during the first weeks of life. Realistic scenarios improving simultaneously several demographic parameters would allow partridge population recovery, mainly through habitat recovery, which would improve nest success and adult and chick survival, combined with reduced hunting quotas.Peer Reviewe