Book: Cuckoo – Cheating by nature


Bill Condie reviews an evolutionary detective story.


NON FICTION
Cuckoo: Cheating by Nature
By Nick Davies
Bloomsbury (2015)

At first glance, 257 pages may seem rather more than you ever wanted to know about cuckoos, the birds whose name has become a byword for the unwelcome interloper. But you will be surprised.

This charming book by the Professor of Behavioural Ecology at the University of Cambridge, Nick Davies, is framed as an evolutionary detective story. It sets out to investigate why the cuckoo came to decide that its best chance of survival was to lay its eggs in other birds’ nests and leave the upbringing of its young to species not their own.

In Europe, the birds are also known as the traditional harbingers of spring and feature in the oldest known song in English – or rather Middle English: Sumer is icumen in, Lhude sing cuccu! In Australia, where some cuckoos arrive from New Guinea in spring, they are better known as storm birds, for their plaintive cry as the clouds gather.

Davies has spent the past 30 years cuckoo-watching on the East Anglian fens. He observes that to many other species of bird the cuckoo is not the harbinger of spring, or of storms, but of doom. Not only do the cuckoos lay their eggs in others’ nests but their chicks go on to eject other nestlings.

Why do the cuckoos choose some birds rather than others and what possible evolutionary purpose can it serve?

In answering these questions, Davies takes us on a wonderful trip hunting for nests and planting fake eggs in them. The results are fascinating.

It turns out that host birds are far from happy to accept fake eggs and will reject eggs that differ from theirs in colour and pattern. “In response the cuckoos evolve such good forgeries that the hosts cannot be completely certain whether they have been parasitised,” writes Davies.

By the time the eggs are hatched, the young birds’ parents are long gone and “some may already be in their African winter quarters while their last chicks are still being tended by reed warblers back in Britain”.

Davies’ description of the “evolutionary arms races” – which the cuckoo has undoubtedly won – is an astonishing one, with great insights into how cuckoo behaviour has evolved.

Alas, as is so often the case with contemporary natural history works, the latter part of the book deals with the steep decline in cuckoo numbers in recent years due to the degradation of their habitats. As Davies laments in an unusual but powerful analogy, future generations will look on our abuse of the environment with as much incomprehension as we look back at heretic-burning in the 16th century.

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