How do the releases of partridges affect the conservation of the little bustard?

    A study carried out in the province of Ciudad Real suggests that part of the package of management measures applied in intensive small game reserves could favor the conservation of the little bustard. However, more studies are required to assess whether the concentration of the little bustard population in these preserves could cause a problem for their conservation.


    La release of farm partridges It has become a common practice in many hunting areas dedicated to small game. Although technically intended to reinforce wild populations of red partridge (Alectoris rufa) during the closed season, in many cases –mainly in intensive or commercial preserves– the releases are made just before the opening of the hunting season or during it in order to increase the economic performance of partridge hunting.

     

    In Spain, between 2,5 and 4 million partridges are hunted annually, extraction values ​​that, unfortunately, are currently only possible due to the release of animals raised on farms.

    Despite being common, it is a controversial game management practice, since it can be associated with various potential problems for wild populations of red partridge, such as the appearance of changes in the behavior, demography and morphology of wild specimens, the introduction and transmission of pathogens or genetic introgression.

    In addition, the potential problems derived from the release of farm partridges can negatively affect other wildlife species. This would be the case of the little bustard (tetrax tetrax), a threatened and protected steppe bird whose populations have been reduced by almost 50% over the last decade in Spain –where the main breeding nucleus of the species is concentrated– and more than 70% at European level.

     

    The little bustard is a threatened and protected steppe bird whose populations have decreased dramatically over the last decade in Spain and Europe.

    In 2007, a scientific study identified the occurrence of a new parasite in the little bustard that could have its origin in the release of farm partridges. If it is not anecdotal, this hunting management practice could constitute a threat to the conservation of the little bustard. On the other hand, the little bustard could be favored by other management measures that are usually carried out to favor the red partridgesuch as crops that are not harvested or predator control.

    Know how the little bustard populations vary in relation to the spatiotemporal dynamics of the release of farm partridges can provide relevant information to shed light on this matter, which would also be very valuable for the conservation of the little bustard. This was the objective set by a group of researchers led by the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM).

    The University of the Basque Country, the Game and Wildlife Conservation Trust (United Kingdom) and the Autonomous University of Madrid also participated in the study.

    Using the study area Ciudad Real province –one of the Spanish provinces where the release of farm partridges is most common, which in turn is a population stronghold for the little bustard in the Iberian Peninsula–, the scientists collected data on the number of farm partridges released in the releases carried out in the period between 2002 and 2016, distinguishing intensive or commercial preserves from those that are not. In addition, they used data from the little bustard censuses carried out in 2005 and 2016 to estimate the population density of the species.

    At the provincial level, the Ciudad Real population of little bustard decreased by 46% between 2005 and 2016. But if we reduce the scale, it is observed that the only areas where little bustard densities did not change significantly between the two years were precisely those that were occupied by the intensive reserves in which the release of partridges had been more intense throughout this entire period.

     

    Certain factors, whether related to habitat or management, should favor the abundance of little bustards in small game reserves where the release of partridges is more intense.

    Contrary to what might be expected, this result suggests that in these intensive preserves there must be certain factors that favor the abundance of the little bustard. On the one hand, it could be that the habitat of these places is particularly suitable for little bustards. On the other hand, intensive small game preserves tend to apply management measures more intensively than other preserves, such as the installation of drinking troughs and supplementary feeding points for partridges, planting fodder (barley, legumes) and intense control of predators. opportunistic. These are measures aimed at favoring the red partridge, but which could have positive effects on other steppe birds, such as the little bustard.

    These results indicate that it would be important to identify the characteristics (habitat or management) of the intensive preserves that have a positive effect on the little bustard to optimize the conservation strategies of the species. In addition, it would be important to assess whether there really is transmission of parasites from farm partridges to little bustards since, if it did occur, the aggregation of little bustards in intensive preserves could be generating an ecological trap for the species.

    The scientific publication of this research is available at:

    Cabodevilla, X., Aebischer, NJ, Mougeot, F., Morales, MB, Arroyo, B. 2020. Are population changes of endangered little bustards associated with releases of red-legged partridges for hunting? A large-scale study from central Spain. European Journal of Wildlife Research 66, 30.