Tuesday, October 23, 2012

The Mysteries of the Cuckoo. Pt. 1

I have been hooked by the BTO’s Cuckoo project and so I have been catching-up with some of the Cuckoo related literature on my book-shelf. I came across ‘The Cuckoo and Other Bird Mysteries' by Bernard Acworth. A book which I expect I bought from a charity or second-hand book shop and then forgot I owned. Excellent, I thought, a  good Cuckoo read. How wrong! It is a completely bonkers book by an unusual author. Ignoring the first half of the book which deals with the ‘other bird mysteries’ ( in which he proves that birds do not migrate – they get blown away!) to concentrate on the latter half we find the following ‘facts’ about the European Cuckoo. The Cuckoo’s unnatural practice of laying its eggs in the nests of other species, which has made the term ‘a cuckoo in the nest’ a common figure of speech makes the cuckoo the enemy of an ‘otherwise ideally moral bird society’ and so it is ‘an abomination.’ Acworth assures the reader that there is a ‘monogamous tradition of birds under wild conditions’ but the Cuckoo breaks this tradition by being polyandrous due to the fact that males outnumber females by six to one. As regards the fosterers, early on we find that by accepting and brooding the innocent-looking Cuckoo’s egg the mother of a legitimate brood will ‘hatch a domestic bombshell for herself, her husband, and her family.’ Initially we are struck by Acworth’s anthropomorphic language. Don’t be in any doubt that he means it. When he uses terms like ‘husband’ that birds have ‘monogamous traditions’ and Cuckoo’s eggs are ‘bombshells’ he believes these expressions to be completely accurate. He continues by saying that the egg is phenomenally small for a bird of its size. But stranger is its almost chameleon-like colouring, which frequently resembles the eggs of its host. But the greatest Cuckoo mystery is’ how does the Cuckoo so successfully and so secretly insinuate its startlingly small egg into the nests, often the tiny and fragile nests, of the little dupes?’
Bottom: The Cuckoo from Willughby's Ornithologia libri tres of 1667

A list is then presented to the reader. It contains six questions that constitute the main features of the Cuckoo problem. It is interesting to ponder all of them but not as interesting as his answers.

1.       How did the unnatural (!) parasitic habits of the Cuckoo originate?
He does not have an answer. He does not like any suggestion that the trait evolved over time in response to external environmental factors, rather opting for something along the lines of ‘desire or design on the part of the Cuckoos in the dim shadows of countless ages past.’
Plates from August Carl Edouard Baldamus's 1892 Life of European Cuckoos

2. How does the Cuckoo adjust the time of the insinuation of the egg into another bird's nest so as to ensure that it will be hatched at the right moment?
Again he has no answer but discusses the explanations prevalent at the time of writing. That at the sight of a prospective foster-bird building, the Cuckoo’ conceives’ her egg, and she is ready to lay in the chosen nest before the owner has commenced to incubate. This is based on a process of watching and searching. Alternatively the female Cuckoo knows when to lay by thieving one of the fosterer’s eggs and testing  it to see whether it is fresh or partially incubated.
 3. How does the Cuckoo contrive, as a general rule, to match its eggs tolerably well, and sometimes perfectly, with the variously coloured eggs of the different nests which house it?                                                                                                                                               Acworth, not surprisingly, treats this as a mystery still unsolved. He rejects any answer based upon evolution or adaptation by natural selection as such answers contradict his religious views. Coincidence is rejected. The theory that the Cuckoo laid its egg on the ground then hawked it around until it found matching eggs is rejected. That the Cuckoo wills a suitable colouring and marking is also rejected. Acworth clearly  had some sense.  The idea that the Cuckoo has evolved the habit of depositing its egg in the nest of the same species of ‘fosterer’ as had fostered that particular Cuckoo and its forebears and consequently in time the Cuckoo’s egg gradually changes to the colouring and marking of its regular fosterer is also, unfortunately, rejected because fostering does not affect physically the object fostered.

4.       Why is the Cuckoo’s egg unique in being generally, though not always, only a fraction of the size to be expected of so large a bird, and why do Cuckoos’ eggs vary in size? Answer: ‘No explanation of this size mystery has, so far as is known, been put forward.’ The explanation afforded by the theory of evolution i.e. of adaptation through selection is rejected because Cuckoos would never have survived in the past as their eggs would have been the wrong size.

5.       How does the Cuckoo insinuate the egg into the small birds’ nests?                          Cuckoos are big, nests of fosterers tend to be small. Often in tangled bush, on fragile reeds, in holes in banks or in and down a tree trunk frequently inaccessible to a big bird. ‘Little wonder, therefore, that ornithologists are perplexed about the method of egg deposition by the cuckoo’. Possible solutions: The Cuckoo swallows its egg and spews it forcefully into the nest – not taken seriously. The Cuckoo lays it in its chosen nest like any other bird – but Cuckoos’ eggs have been taken from nests in holes to which it would have been impossible for the Cuckoo to have obtained access. The Cuckoo lays its egg on the ground then carries it in its beak to the prospective nest where it places it – Acworth leans towards this even though there is little to no evidence. The Cuckoo projects or squirts its egg into nests – this will explain how eggs are found in some inaccessible nests.  The Cuckoo uses a combination of all four methods. Again Acworth ends this question by writing: ‘Little wonder, indeed, that the method of egg deposition in inaccessible nests remains a problem hotly disputed by ornithologists.’

6.       Why should the sinister word ‘cuckold’ be derived from the Cuckoo if the small female bird is a foster-mother? Bit of a side issue this. The male Cuckoo is not, in fact, cuckolded – none of the birds are. People subconsciously associate the secret life of the unfaithful wife with the secret of the Cuckoo.  Now here’s interesting! Acworth suggests that if evolutionary theory be true it is possible that the Cuckoo has evolved its ‘chuckle’ as a mocking response to human beings lack of understanding of the birds’ secrets. Blimey!

Now here’s the rub. Acworth states that five of the six problems given above would all be solved at a stroke if we accept his theory, the off-the-wall theory  that Cuckoos are nearly all hybrids of pure male Cuckoos and female foster birds! The correct moment of incubation, the varying number of eggs laid by a Cuckoo in any season; the matching of the eggs in colour, marking and size and the insinuation of eggs into inaccessible nests are all solved. And the little male ‘foster-father’ really would be a cuckold.
                         Elizabeth Gould or Edward Lear.  Goulds Birds of Europe: The Common Cuckoo 1837

So there we have it there are lots and lots of Robin-Cuckoos and Meadow Pipit-Cuckoos and Dunnock-Cuckoos out there. That will please the splitters! This book was written in 1944 and the last 68 years has seen significant progress in our knowledge and understanding of the life of the Cuckoo. Anyone following the fortunes of the BTO's Cuckoos fitted with satellite tracking devices will be aware of how much new information we are getting even as I write. Acworth would have been dumbfounded and astonished. But I doubt if he would have changed his views. Follow the BTO Cuckoo tracking project here: http://www.bto.org/science/migration/tracking-studies/cuckoo-tracking


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