Inferred hybridisation, sympatry and movements of Chorister Robin-Chat Cossypha dichroa and Red-capped Robin-Chat C. natalensis

Abstract

Inferred hybrid Chorister Robin-Chat Cossypha dichroa and Red-capped Robin-Chat C. natalensis have previously only been recorded from the Eastern Cape province, South Africa. We extend the occurrence of inferred hybrids with ringed and photographed examples from KwaZulu-Natal and Limpopo provinces. Sympatry at a fine scale was investigated at Vernon Crookes Nature Reserve, KwaZulu-Natal, using observational data over 30 years (1978–2008) and intensive mist-netting during two field-trips in June and October 2010. Both robin-chat species were found throughout the year and occurred in the same forest patches. Inferred hybrids are known from five different forest patches in Vernon Crookes, three with photographic evidence. During winter an increase in Chorister Robin-Chat numbers was detectable both from mist-netting and checklist data. An increase of Red-capped Robin-Chats was observed from mist-netting and more equivocally from checklist data in spring. Red-capped and Chorister Robin-Chats are sympatric along the eastern escarpment of South Africa, with co-occurrence in 96 quarter degree squares from Southern African Bird Atlas Project 1 data. During the breeding season, co-occurrence was recorded in 62 quarter degree squares and in nine grid-cells evidence of breeding by both species is available. Hybridisation may be more common along the extensive area of sympatry than currently realised.