Originally published July 2014
Hello everyone! As I reach for a jumper on a decidedly chilly, June day I cannot help but wonder how our spring visitors from the warmer climes cope with the vagaries of our British climate; in particular that much maligned bird, the Cuckoo (Cuculus canorus). The Common Cuckoo belongs to the taxonomic Order Cuculiformes and quite obviously gets its name through some early observer of nature making good use of onomatopoeia! Having done a very quick and totally unscientific survey amongst friends and relations, it does seem as if, these days, fewer of us are hearing the song that inspired its name. Sadly this is not just lack of serendipity, but the result of the bird being one of our fastest declining migrants. The British Trust for Ornithology (BTO) estimates that the UK has only half the number of Cuckoos visiting our shores than we did a mere twenty five years ago.
It is worth looking at the lifestyle of this familiar bird as, much in the manner it uses other birds’ nests, it has become entrenched firmly in our folk lore and culture. This is all the more remarkable as it spends so little time in our country, around three months of the year. After overwintering in Africa, the birds make the long and hazardous journey to breed. Just how hazardous a journey we could only speculate until recently. The BTO have spent the last three years monitoring the travels of several radio-tagged Cuckoos as they complete their annual 10,000 mile round trip from their feeding grounds in the African continent to the breeding sites throughout the UK and Ireland, and back again. We now know that these accomplished travellers use a number of routes down through Europe, seemingly dependent on where they start from in the UK.
Cuckoo numbers are dwindling at a greater rate in England than they are in Scotland and Wales and early results with radio tracking offer an explanation. It appears that the majority of English birds take a westerly route through Morocco and then east to Libya as opposed to their Scottish and Welsh counterparts who prefer to fly over the Mediterranean through Tunisia and Egypt and on to the Congo. The mortality rate has been high on the western route over the last three years, possibly due to adverse weather conditions or perhaps a dearth of food supplies. Only long term monitoring will provide a better picture, although there are signs that individual birds have actually changed their routes in the short time they have been tracked. Considering the distances involved, this is a major feat of navigation and demands our respect in a world where our own species becomes increasingly dependent on technology to undertake the shortest of journeys!
The absence of the bird throughout the autumn and winter and sudden reappearance in spring gave rise to many tales in the past. Folklore is rich in theories of how Cuckoos overwintered in hollow trees or even transformed into birds of prey for most of the year. Our ancestors may be forgiven for such leaps of the imagination as the bird’s sleek body, pointed wings and long tail give it the appearance of a Sparrowhawk or Kestrel. It is the male Cuckoos who herald the traditional start of spring, as the females have a very different bubbling type of call. It was believed that St Tiburtius Day, the 14th April, was the day the first Cuckoo called although the Celts associated the bird with April Fool’s Day. In Scotland, the day was originally celebrated on 13th April and called Gowk’s Day, a Gowk being a Cuckoo bird or a foolish person who was gullible enough to be the target of any number of pranks on the day.
Of course what the Cuckoo is most famous, or infamous, for is its status as a brood parasite, that is to say its penchant for laying its eggs in other birds’ nest. Females have the ability to store sperm and will continue to lay eggs after the males have left the country from early June onwards. It could be that their resemblance to Raptors is beneficial when darting in to lay their egg, although it is a common sight to see a Cuckoo being mobbed by several wary birds. Nevertheless, once the deed is done, the hundred or so host species that have been recorded appear to be fooled into a willing state of foster parenthood. The reason for this is a tribute to Ma Nature’s ingenuity and the wonders of evolutionary biology. Once a female bird chooses a host species, whether it be Robin, Dunnock or Reed Warbler to name but a few, they continue to use that same species for the rest of their lives. Not only does the female lay an egg that looks very similar to the host bird’s eggs but the resultant fledgling mimics the begging cry of the other chicks. The newly hatched Cuckoo then proceeds to dispatch its fellow fledglings and eggs by pushing them out of the nest with ruthless or, to be strictly accurate, instinctive determination. This leaves it the sole beneficiary of the parent birds’ administrations and they continue the thankless task of feeding a chick which very soon outgrows both foster parents and nest.
So there it is, a very brief look at the life of one of our most familiar birds, albeit a fleeting visitor. The BTO website is certainly worth following. At present many of the returning males are in mid-Europe. I am sad to say that I personally have not heard a Cuckoo this year, but my ad hoc survey did show that people have heard at least one male in Crowhurst over the past few months. Let us hope the trials of the incredible journey does not prove too much for our annual visitors.
Hold on, I hear you cry, what has all this to do with some obscure disease the name of which is sprawled across the top of the page? I was hoping you would ask! Up until 1788 it was believed that the parent bird committed the murderous act of ejecting eggs and chicks from the host nest. Then a certain Dr Edward Jenner made a series of observations which he forwarded to the Royal Society and was subsequently elected as a Fellow. His letter contained an in-depth study of the newly hatched Cuckoo chick completing the heinous task. He even describes how the chick uses a special hollow in its back to rest the egg or fledgling in before flinging it to its doom. The hollow disappears after twelve days and appears to have been provided to the chick for that very purpose. Our own younglings will be able to recall from recently devoured history books how Jenner went on to be credited with developing the smallpox vaccine after observing how dairy maids infected with cowpox were immune to the far more deadly disease. As with all of the early naturalists, Jenner’s observations and recording skills are a delight to encounter.
The mode of accomplifhing this was very curious. The little animal, with the affiftance of its rump and wings, contrived to get the bird upon its back, and making a lodgement for the burden by elevating its elbows, clambered backward with it up the fide of the neft til it reached the top, where refting for a moment, it threw off its load with a jerk, and quite difengaged it from the neft.
Excerpt from Observations on the Natural History of the Cuckoo, By Mr Edward Jenner. In a Letter to John Hunter, Esq. F.R.S. (1788)
Enjoy your Summer, keep your eyes and ears open for Nature’s delights and do mind your Fs and Ss!
Tell it to the locked-up trees,
Cuckoo, bring your song here!
Warrant, Act and Summons, please,
For Spring to pass along here!
Rudyard Kipling, The Cuckoo Song (1922)
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