Positive interactions between vulnerable species in agrarian pseudo-steppes: habitat use by pin-tailed sandgrouse depends on its association with the little bustard

Positive interactions between species can have important conservation implications, especially when the species associating are both vulnerable. We studied the habitat use of pin-tailed sandgrouses Pterocles alchata and their association with another vulnerable species, the little bustard Tetrax tetrax in agrarian pseudosteppes of central Spain using radio-tracking. The occurrence of mixed-species flocks varied seasonally, being more frequent in winter (65% of pin-tailed sandgrouse flocks). In this season, pin-tailed sandgrouses preferred stubble fields and fallows. Moreover, we found that habitat selection of pin-tailed sandgrouse depended on the association with little bustards in mixed-species flocks. When in mixed-species groups, sandgrouses changed their agrarian substrate preferences, and used stubble fields significantly more often than when in sandgrouse-only flocks. We also provide evidence that pin-tailed sandgrouse benefited from the anti-predator vigilance of little bustards, allowing sandgrouse to exploit new feeding grounds (stubble fields) that would otherwise be too risky to exploit. Our results indicate a close positive association between these two species, which are both declining in Europe, and we discuss implications for their management and conservation. We also recommend taking into account inter-specific positive interactions when designing conservation strategies for threatened species.