Sorry to any of you who were eagerly awaiting the next instalment of our Picturing Science series; we hope this picture was worth the wait! The image comes from Dr Claire Spottiswoode, a Dorothy Hodgkin Fellow from the University of Cambridge.
This wild looking bird is the chick of a Melba Finch, the host species of the brood parasitic Paradise Whydah. Brood parasites lay their eggs in the nests of other birds and rely on the host parents to feed and raise their young at the expense of their own chicks. The Whydah precisely mimics the mouth markings and downy feathering of the Melba Finch chicks to stimulate the host parent to feed it as though it were one of its own.
Many brood parasitic birds beautifully mimic the eggs rather than the chicks of their hosts, to avoid early detection and rejection by host parents who are adept at spotting a possible cheat. Claire’s studies how hosts can further defend themselves by evolving a diversity of colours, spots and squiggles on their eggs to make them harder to mimic, much as the watermarks of banknotes deter forgers. Parasites in turn catch up, leading to an ongoing arms race between the host evolving new signatures, and the parasite new forgeries.
In this image, the eggs on the left are host eggs, and those on the right are those of the parasitic Cuckoo Finch that Claire studies in Zambia. The top two rows come from the nests of one host species (the Red-faced Cisticola), and all the others from another host (the Tawny-flanked Prinia). This shows not only how the Cuckoo Finch has evolved to mimic different host species, but also the individual signatures of different host females, too.
As well as field studies, Claire also uses genetic approaches to study the evolutionary history of parasitism, and has shown that some of the interactions between African brood parasites and their specialist hosts are millions of years old.
Currently, she is trying to tackle the puzzle of how distinct host-races (such as the Cuckoo Finches that trick different host species, above) are genetically maintained within a single parasitic species. This might add to add to our understanding not only of how parasitic birds fool their hosts in the African bush, but also of similar coevolutionary battles such as those between our immune systems and the pathogens that cause our diseases.
If you are interested in reading more about Claire’s research why not visit her webpage.