I was inspired to pick up this book after seeing a rufous female common cuckoo on my recent trip to the Danube Delta and listening to an enjoyable interview with Nick Davies on The Life Scientific podcast during a hair-raising drive home through an unseasonal blizzard.
Davies is Professor of Behavioural Ecology at the University of Cambridge and has studied cuckoos on Wicken Fen since 1985 (the year of my birth, pleasingly). The Cuckoo is a mixture really of Davies’ memoirs as a field ecologist and the science behind brood parasitism. He describes how his experiments have led to interesting findings about cuckoo evolution and the arms race they are engaged in with their hosts. He describes the functions behind aspects of cuckoo morphology and why some specialist sub-species are better at mimicking host eggs than others, this largely being due to the amount of time that the host species has been under significant selective pressure to reject odd-looking eggs. He draws upon lots of fascinating examples of other parasitic bird species and non-parasitic cuckoos from around the world from Japan to West Africa. Davies makes the very valid point that perhaps we should regard UK cuckoos as being an African species given that they spend twice as long living next to lowland gorillas than alongside cattle in Britain! One of the most interesting parts of the book for me was the explanation as to why cuckoos roughly resemble sparrow hawks, particularly the presence of barring, having not previously noticed the similarity myself.
Davies’ accessible, clear style of writing reminded me of first reading The Selfish Gene in my second year of university. I remember feeling as though what seemed like lots of stiff, fusty facts suddenly fit neatly together into a beautiful and exciting overarching concept. Before reading The Cuckoo I thought – “Cuckoos. They’re brood parasites that overwinter in Africa”. Reading The Cuckoo, I have learnt that there is a lot more to them!
Davies cites the work of Richard Dawkins and John Krebs a few times in the book which gives a good refresher on the ideas of kin selection. In chapter nine Davies claims to have disproved Dawkins and Krebs’ suggestion that cuckoo chicks rely on manipulation (as opposed to deception at the adult stage) to trick the host species into feeding it. Dawkins and Krebs likened the urges of a reed warbler, for example, to feed any begging mouth within its nest to the compulsion of a drug addict to get their next fix. Davies tells us that his findings show reed warblers will readily accept the chicks of other species besides the cuckoo, such as dunnock, and thus the drug analogy is wrong. Now, perhaps an analogy is not the most robust of ways to present a scientific idea but I think Dawkins and Krebs’ holds firm. The cuckoo chick is manipulating the reed warblers’ instinct, insofar as it is taking advantage of the host’s inability to resit feeding a gaping mouth within its nest, even if dunnocks are not doing so as a life-history trait. I can’t help but think deception would be the wrong word to describe the cuckoo chick’s behaviour because the reed warbler does not necessarily believe the cuckoo is its own genetic offspring but it might simply be so full of hormones that it can’t resist the urge to provide it with food. Davies describes how even now when observing in the field he is perplexed by the sight of a reed warber feeding a cuckoo chick eight times its own size. Maybe I have misunderstood Davies’ argument. Perhaps Dawkins and Krebs’ are correct in their thinking but should move away from the ‘junkie’ analogy to explain it. See what you think.
The book ends with a reflection on how and why the UK cuckoo population has reduced so drastically over the thirty summers during Davies’ observations – a sombre but unsurprising end. I have heard older family members talking fondly about how the call of a cuckoo was a common sign of spring when they were growing up. It makes sense alongside the figures that I was 31 years old and in Romania by the time I had my first good look at one.
If you are looking for a popular science book that is sufficiently evidence and data loaded to back up statements without requiring regular re-reading of paragraphs (Yes, I am thinking of A Brief History of Time) this is an ideal choice. I read one chapter per night and always looked forward to the next. I’ll be adding The Cuckoo to our school’s library collection in the hope that raising awareness in young readers (15+) makes some small contribution towards reversing that downward trend in cuckoo numbers. 4/5