I think I'm going cuckoo

Thrice welcome, darling of the Spring!
Even yet thou art to me
No bird, but an invisible thing
A voice, a mystery.

                     Wordsworth (who clearly didn't live around here)


Firstly, let me point out that this post is not about lemurs.
In fact it isn’t even about Madagascar.

I’m taking a break from my lemur litany to indulge in a bit of a gripe.

I need it.

You see my neighbourhood ‘invisible thing’ is driving me to distraction.


I’m sure you know how it feels to be assailed by an apparently innocuous sound, endlessly repeated.
Whether it’s the plink of a dripping tap or a tune circling in your mind, incessant repetition can push the sanest of us into madness. (And after eight years as a recluse, sanity is not my strong suit.)

My own personal bugbear comes feather-coated. He swept in about a month ago, all fresh and perky after a winter vacation in equatorial Africa. Dressed elegantly in soft grey, with a waistcoat of pinstripes and salmon cravat, he’s far too dapper for his slightly embarrassing moniker: the red-chested cuckoo (Cuculus solitarius).

 

Like other cuckoos, the red-chested (Cuculus solitarius) is dressed to impress. His slick hawk-like shape, raptorish eye-ring and sparrow-hawk chest stripes are no accident. Experiments show that the stripes alone are enough to intimidate potential cuckoo-rearers, allowing the wearer access to nests. Photo by Johann du Preez.


My red-chested cuckoo is out for a good time.
Having staked out a bachelor pad in the trees along the river, he dallies at special ‘song posts’ hidden in the foliage (essential, to avoid the shot-gun blasts of irate listeners) and sends forth his message. Repeatedly.

Now his descending, three-note call is not unpleasant per se (you can listen to it here).
But repeated stridently - at one second intervals – for hour after hour after hour, it’s simply soul destroying. And don’t imagine that nightfall brings relief. Mere darkness is no deterrent to a red-chested cuckoo on the make.

Tossing and turning sleeplessly, I’ve had plenty of time to ponder the purpose of his incessant advertising. Is he warning off rivals or serenading the ladies? At the risk of eroding your sympathy, I’ll admit (solely for scientific purposes) that he does occasionally take a break; sometimes for several days at a stretch (ah, blessed relief).
But this is weird behaviour for a bird that defends its territory with song. Does he only engage in operatics when he has an audience?
I’ve come to the conclusion that what he’s really shouting is,
“Have I got a nest for you!”

You see, in red-chested cuckoo society, it’s the male who screens prospective foster parents. When not driving innocent bystanders insane, he skulks about spying on the neighbours. Once he spots a happy couple preparing their nursery, he hurriedly leads (one of) his true loves to the spot and helpfully distracts the parents-to-be while she sneaks in and lays an egg. To make the crime scene less conspicuous, she then scoffs a resident egg (why waste a good egg?).

Like all his kind, this cute red-chested cuckoo chick won his spoiled, only-child status by murder (struggle, push, shove... ‘Oh look, chick/egg overboard. Now how did that happen?’).
Photo by Arno & Louise Meintjes.

As I’m sure you know, cuckoos produce eggs that look similar to those of their victims to assist them in their evil egg-switching.
This is all good and fine if you’re a cuckoo species that freeloads on only one type of bird. But my annoying red-chested cuckoos don’t put all their eggs in one basket (that way, they could become extinct... or so I fantasize).
No, my cuckoos foist their ankle-biters off on to 18 different species of sucker, all of whom produce very different looking eggs. So how do the cuckoos mix and match?

Well not all red-chested cuckoos are born equal. In any one place, you’ll find several different races (called gentes), each of which specialises in hoodwinking just one particular host, and produces the eggs to match.
But how do the cuckoos maintain this racial purity? What happens when a girl from the Cape robin gens (gens is the singular of gentes) is swept off her feet by a boy from the wagtail gens. Will the couple’s daughters ever find a suitable nest for their miscegenated eggs?
Alternatively if maiden cuckoos always abide by family tradition and only choose lovers from within their own gens (i.e. there’s no racial mixing), surely the races are really different species?

The answer is devious. Unlike mammals - where it’s the male who totes the whacky, sex-defining Y chromosome - birds do things the other way around. Macho birds carry two Z chromosomes while the ladies are ZW. Egg colour is craftily encoded on the W chromosome, so it’s always passed on – unadulterated - from mother to daughter regardless of what or whom Dad is (as he can only ever contribute a Z chromosome).

A recent study of greater honeyguides (OK, not a cuckoo but employing the same nefarious means of reproduction) found that their gentes are extremely ancient. When the researchers looked at the honeyguides’ mitochondrial DNA (which comes only from Mum) they found that the gentes had remained entirely separate and unsullied for millions of years. But when they looked at the chromosomal DNA (which comes from both Mum and Dad) they could find no difference between gentes (because everyone happily interbreeds).

The eye of the beholder. Some gentes of red-chested cuckoo lay eggs that don’t match those of their target species. So why do the victims accept them? Unlike us, birds are able to see near ultraviolet wavelengths. When researchers examined the eggs using ultraviolet-visible spectrophotometery, they found that they were similar. Oops.
Photo by Johann du Preez.

Among their other weird traits, cuckoos are renowned for their fondness for hairy caterpillars (they munch them, not keep them as pets). They develop this predilection only in adulthood because no sensible foster parent offers a chick such noxious fare. Furred caterpillars are eschewed by almost all birds thanks to their urticating hairs (I love that word; it means ‘stinging like a nettle’). The tips of these hairs are detachable and dispense irritating poison. Although cuckoos scrub their dinner thoroughly (you can see footage here), the lining of their gizzard still ends up bristling with cactus-like spines. To rid themselves of these, European cuckoos slough off and regurgitate bits of mucous membrane lining (a trick most of us employ only after dining on dodgy prawns).



Local cuckoo food.
Who wouldn't want one as a pet?


It was perhaps this ability to stomach noxious things that encouraged our ancestors to link cuckoos with wedlock. The sceptre of the ancient Greek goddess of marriage is normally topped by a cuckoo rampant, and folklaw stipulates that to hear a cuckoo is good luck for those about to tie the knot, and a portent of adultery for those already wed. Since I fall into neither category, I’ll opt for the alternative claim: the number of cuckoo calls you hear signifies the number of years until you marry or die (whichever comes first).

By my calculation, I should still be going strong in 9011.
How long my sanity will last is another question entirely.