Declines of the globally threatened Rudd’s Lark Heteromirafra ruddi in one of its last remaining strongholds

Rudd’s Lark Heteromirafra ruddi is a globally threatened species endemic to eastern South Africa’s highland grasslands, where climate envelope modelling has predicted a dramatic reduction in its already small and fragmented distribution. Here we assess recent changes in one of its last strongholds, the Wakkerstroom grasslands. We assessed changes in Rudd’s Lark population and habitat condition over 12 years, within a core section of an area intensively surveyed in 2002–2004. Our 2016 survey found lower absolute numbers of Rudd’s Larks (five transects with Rudd’s Lark present compared to nine in 2002; nine individuals compared to 32), as well as a lower probability of encounter. Transects with shorter grass and higher altitude had a higher probability of Rudd’s Larks occurrence, consistent with findings in 2002. Point locations where Rudd’s Larks were recorded had shorter grass, higher forb cover and more bare ground cover, and tended to be at higher altitudes than random locations in the surrounding grassland. Remotely-sensed fire data showed that late-season fires, which pose a threat to Rudd’s Lark nestling survival, are generally uncommon. Field observations indicated that seven transects (of which two previously contained Rudd’s Lark) that had previously been grassland had been converted to intensive crop production. While Rudd’s Lark may be affected by direct loss of grassland habitat through conversion to crops, the species has also declined within remaining grassland habitat. The drivers of decline remain unclear but this recent observed local decline of Rudd’s Lark in the immediate Wakkerstroom area supports the species’ recent IUCN uplisting to globally ‘Endangered’, given that its previous downlisting was based on habitat requirements and breeding success from this area.