ScienceDaily (Nov. 18, 2010) — 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, 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.
Many apparently harmful parasites seem to be tolerated by their hosts and the provision of compensatory benefits to victims could underpin a range of host-parasite relationships. The insight the research provides into complex co-evolution between species gives scientists a valuable way of understanding other important relationships, such as those between drugs and bacteria and between pathogens and hosts.
Dr Andrew Radford, who led the research funded through a BBSRC David Phillips Fellowship, said: "Because drongos are parasitic birds who swoop in to steal food from other species, you'd expect them to keep a low profile while waiting. Rather surprisingly, however, drongos perched above foraging babblers advertise their presence by issuing a call called a 'twank' every 4 or 5 seconds.
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http://www.sciencedaily.com/releases/2010/11/101118083905.htm