Biological arms race between the cuckoo finch and its host

I was really fascinated to read about the biological arms races between cuckoos and host birds in Africa. The researchers from University of Cambridge say these sometimes take the form of host evolving new, unique egg patterns (or 'signatures') and the parasite evolving new forgeries.
Here is one strategy. Host females lay a different type of egg, with variations in egg colour and pattern. This makes it harder for the cuckoo finch to come out with accurate forgeries. The researchers say these variations seem to act like the complicated markings on a banknote: complex colours and patterns act to make host eggs more difficult to forge by the parasite, just as watermarks act to make banknotes more difficult to forge by counterfeiters.
The researchers say some host species, such as the tawny-flanked prinia, have evolved defences by shifting their own egg appearance away from that of their parasite. The evidence of this can be seen in the evolution of an amazing diversity of prinia egg colours and patterns.
Red-faced cisticolas lay only moderately variable eggs but are very adept in discerning whether an egg is their own or not. They can easily spot even a sophisticated mimic.
The paper makes interesting reading. It gives us a fascinating insider view of evolution and adaptation
The findings are reported in the journal Proceedings of the Royal Society of B.


 ‘How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences’
Claire N. Spottiswoode and Martin Stevens