Some very interesting findings in this book, and I learned many things. Some examples:
1) Cuckoos are not the only birds who parasitise other birds' nests - there are quite a number of other birds which do that!
2) Some birds practise partial parasitism (i.e. they raise the majority of their young but drop a few eggs from their brood into other birds' nests).
3) Cuckoos have "favourite hosts" (i.e. they tend to select only certain species to parasitise).
4) There are different "races" of cuckoo, and each appears to be highly specialised in their parasitising habits.
5) Some birds have developed "signatures" (i.e. unique patterns) on their eggs to help them distinguish their own eggs from cuckoo eggs.
6) Cuckoos, in return, have also developed similar-looking "signatures" on their own eggs, as part of their attempts to mimic their hosts' eggs!
7) The "arms race" between cuckoos and their hosts continue.
However...
The questions I really wanted answered, like why certain birds continue to raise parasitic cuckoo chicks to adulthood despite obvious physical differences, were not satisfactorily answered. Also, why is it that blackbirds will not raise cuckoo chicks while other birds would? This went completely unaddressed; there weren't even any theories about why this was so.
What the book is very heavy on are facts. The author sets up a lot of field experiments and presents his findings clearly and succinctly. Everything is easy to read and understand, yet the writing not dry, tedious or boring. I must say I enjoyed reading this quite a lot, even though many questions remain unanswered.
In the middle of the book are several colour photographs, among which are cuckoo eggs compared to host eggs, cuckoo chicks compared to host chicks, etc. One photo showed a huge cuckoo chick being fed by its adult host - the chick was so much bigger than its adopted parent and could even swallow it whole! This made me question all the more why the adult host couldn't possibly tell that the chick wasn't its own!
This book would be good if you want to understand more about how exactly cuckoo parasitism works, and how their hosts get parasitised. It doesn't do such a good job of providing CONVINCING arguments as to why this is so, and the author himself admits that, in many areas of research, we as yet still do not have answers.