This particular bird is probably one of a natural hybrid swarm of Terpsiphone rufiventer x Terpsiphone viridis. Abuko is a remnant gallery forest surrounded by savannah woodland. In The Gambia T. rufiventer is restricted to gallery forest whilst T. viridis can survive in more open woodland. At Abuko the two interact and hybridise producing fertile offspring which backcross with the parent species producing a hybrid swarm which may phenotypically resemble one of the parent species but genetically is a hybrid.
This individual had the typical plumage features of T. rufiventer but with some black belly-streaks suggestive of T viridis input in its lineage.