Camelthorn and blackthorn trees provide important resources for southern pied babblers (Turdoides bicolor) in the Kalahari

Abstract

In the southern Kalahari Desert, cooperatively breeding Southern Pied Babblers Turdoides bicolor frequently build their nests and forage in camelthorn trees Vachellia erioloba, a keystone species in the region, and blackthorn trees Senegalia mellifera, a widespread early successional shrub. Using Ivlev's electivity indices (Ei), we show that Southern Pied Babblers preferentially nest in camelthorn trees and preferentially forage in or under camelthorn and blackthorn trees. Southern Pied Babblers primarily forage on the ground; however, they will make use of arboreal resources when these are available. We observed the birds spending the highest proportion of foraging time off the ground during October, when breeding is also most common, compared with all other months within the austral summer breeding season. They are most likely to be observed foraging in camelthorn trees earlier in the breeding season and blackthorn trees later in the breeding season. We demonstrate that Southern Pied Babblers have a strong relationship with camelthorn trees, in which they prefer to both nest and forage. We highlight the importance of protecting camelthorn trees, a keystone species in the region, as part of the conservation and management of endemic Kalahari fauna such as the Southern Pied Babbler. In addition to contributing to the literature on keystone species, our observations raise questions about the ways in which avian reproduction in the arid zone could be decoupled from rainfall via the phenology of deep-rooted tree species.