Davies (Behavioral Ecology/Univ. of Cambridge; Cambridge Cuckoos, Cowbirds and Other Cheats, 2000, etc.) chronicles his 30-year attempt to solve what he calls “an enduring puzzle: how does the cuckoo get away with such outrageous behavior?”
During his years at Cambridge as a student and a faculty member, the author became fascinated by the cuckoos that frequented a nearby wetland during nesting season. This is an account of his and his collaborators’ efforts to solve the mystery. Davies’ special interest as an ornithologist has been to try to understand how they were able to trick the unwitting host species into accepting foreign eggs—particularly after the fledgling cuckoo emerged from his egg and set about to ruthlessly destroy the host's remaining eggs. One of their earliest discoveries was that the eggs laid by different subspecies of European cuckoos have evolved to closely mimic those of different host species (warblers, pipits and wagtails) in size, color and markings. Not only do they foist their eggs on other species; they also ruthlessly destroy the host eggs to make a place for their own. A female cuckoo will time her egg-laying to that of the host female, removing a host egg and replacing it with her own. The faster-maturing cuckoo will hatch first and destroy nest mates that are potential rivals and then mimic their calls begging to be fed. Relieved of parenting duties, the adult cuckoos conserve energy for an early return to their winter habitat. While host birds do attempt to destroy the intruder’s eggs, they are confused due to the variability of their own eggs. A battle for survival ensues between the aggressor cuckoos and the defending hosts, involving genetic and behavioral shifts.
“My hope is that this reads like a nature detective story,” writes Davies. He has achieved his goal and more in this fascinating study of “an evolutionary arms race.”