This is a fork-tailed drongo video.
Gangster birds running protection racket give insight into coevolution
Like gangsters running a protection racket, drongos in the Kalahari Desert act as lookouts for other birds in order to steal a cut of their food catch. The behaviour, revealed in research funded by the Biotechnology and Biological Sciences Research Council (BBSRC) published in Evolution and reported in Nature‘s Research Highlights today (18 November), may represent a rare example of two species evolving from a parasitic to a mutualistic relationship.
The team from the Universities of Bristol, Cambridge and Cape Town showed that victimised pied babblers gained a mitigating benefit from the presence of thieving drongos because, by keeping watch for predators, the drongos allowed the babblers to focus on foraging and so catch more insects.
See also here.