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.

When your stalker has feathers...

The parched colours of the dry season.
Photo by Kim Reijs.

When I venture into the field these days it's like I've somehow slipped into a Disney animated classic.

All I need is a ballooning skirt and a tripping walk to make the illusion complete.

Why am I suffering these weird fantasies?

Well, the moment I set foot in the bush, I'm surrounded by clouds of little blue birds, all atwitter with excitement. And then the little animals come creeping out of the undergrowth to gather at my feet.
Magic?  Charisma?  Sadly no.
You see it's the height of the dry season here. With the bush seared, dusty and leafless, everyone could use a drink.

In an effort to curry favour with my study subjects (essential if I'm to ever find the little brutes), I reward them with a small bowl of water whenever I join a group. And of course it doesn't take long for the other locals to catch on too.

The mongooses crowd around the bowl, some delicately lapping with pink tongues while others dip in their paws and lick the moisture from their toes. Meanwhile a menagerie congregates around us.
Four-footed or two, feathered, scaled or furred, no one can resist the lure of free drink.

Tamarind (HF047) enjoying a tipple.

The tree squirrels (Paraxerus cepapi) aren't backward in coming forward.

Rough-scaled plated lizards (Gerrhosaurus major) disdain rules of etiquette.

Rainbow skinks (Mabuya quinquetaeniata) tentatively seeking that elusive pot of gold water.



"... and then I told that great brute of a mongoose to just clear off..."



The blue waxbills (Uraeginthus angolensis; pictured above) are the most persistent (and impatient). They accompany me as I search for the mongooses, flitting through the bare twiggy undergrowth, peeping vociferously. We collect more and more followers as we go, with everyone complaining loudly about having to wait to wet their whistle. I find this entourage a bit irritating because it drowns out the subtle, tell-tale peeps of my mongooses.

But if the waxbills are annoying, there's one avian devotee that drives me insane. Dressed in humdrum colours, it flutters from branch to branch above my head, ruffling its wings, wriggling its white-edged tail and bobbing about like a creature possessed. It also feels compelled to squawk non-stop. One of my bird books likens its raucous call to the sound of a shaken box of matches, which is pretty accurate if you pump up the volume about 100-fold.

This irksome devotee will dog my steps for hours (OK, for the purposes of scientific accuracy, I'll admit that this is a slight exaggeration). It certainly doesn't retire once I find the mongooses (and they dislike it as much as I do). You see it's not after a mere sip of water. It wants wax.

Yep, you read right: the greater honeyguide is one of only a handful of critters who's able to dine on, and digest, wax (thanks to special microbes in its gut).

But before you start imagining some ghastly Hitchcockian scene, let me make it clear that it isn't after earwax.
This feathered stalker hungers for beeswax.

Its fervent taunting is designed to persuade me to follow it to a likely bee hive. Once there, it expects me to smoke out the bees and heroically retrieve the honeycomb so it can gorge itself on bee larvae and wax (it doesn't eat honey). I've never felt tempted to accept this offer (opening a jar of jam seems safer), but if I'm unwise enough to move or speak in the bird's presence, it gets super excited and zooms off, in a sweeping, undulating flight, toward the nearest hive.

Although greater honeyguides (Indicator indicator) are only about 20 cm (8 in) long, they vex the inhabitants of woodlands and savannahs throughout sub-Saharan Africa. When not guzzling wax or terrorising baby bees, they make do with flying insects.
Photo by Carol Foil.

Now as a zoologist who studies partnerships between species (see an example here), I know I should revere this bird. Collaboration between beasts of feather and fur is rare, and the greater honeyguide is the poster child for such complicity.
But God it's annoying!
And the creature's not easily deterred; honeyguides will invade villages and gardens in search of someone with a sweet tooth, and they even pursue cars and boats.

You see the honeyguide has had the dubious pleasure of sharing its habitat with humans for millions of years, and that's plenty of time to notice a mutual fondness for bee by-products. But what's really impressive about the alliance that's evolved, is how well human and bird communicate.

For example, when the Boran people of northern Kenya decide to do a spot of honey pilfering they inform the birds by whistling piercingly through clasped fists (this doubles their chances of bumping into a honeyguide, who then reduces the time they spend searching for a hive by two-thirds). Of course the bird has reason to come running flying: only 6% of the hives (of Apis mellifira) in its territory are accessible to beak and claw alone.

Upon arrival, the honeyguide gives its annoying come-hither call, zips off for a moment (presumably to identify landmarks along its proposed route) and then leads the honey gathers in a beeline for the closest hive. (A three-year study found that the birds monitored all the hives in their area, routinely stopping by for a minute or so to check they were active).
Intentionally or otherwise, the honeyguide also informs its followers how far they'll have to walk. The further away the hive, the longer the bird is gone on its initial reconnaissance mission, and the nearer the allies gets to the booty, the shorter the bird's perch-to-perch flights become. When the team finally rocks up at the hive, the bird gives a special 'here it is' call, perches close to the nest and then keeps mum.

If you haven't already seen footage of a greater honeyguide doing its thing, you can view one (and David Attenborough imperilled by bees) here (courtesy of the BBC's Trials of Life).

The weirdness of greater honeyguides is not limited to their dietary habits. These birds are territorial and each male has a special 'song post' where he sits from dawn 'til dusk throughout the breeding season vociferously boasting of his macho charms. Interested lady honeyguides simply drop by for a bit of fun every now and again.
But once knocked up, female honeyguides appear to go to pieces, abandoning the fruit of their passion at the earliest opportunity. They cunningly slip their egg into the nest of unsuspecting hole-nesting birds (such as barbets and woodpeckers). When their little darling hatches, it dispatches its nest mates with a wicked billhook designed for the purpose.
Serendipitously, you can see wonderful photos of this villainous behaviour here.

The adoptive parent (a meves starling) of a greater honeyguide chick bringing home the bacon frogs legs.
Photo by Johann du Preev.

But all is not well in the land of honey procurement.
When I first started working on the dwarf mongooses six years ago, I was constantly beset by these irritating birds; now it's a rarity. I hadn't really given this much thought: sure, the resident birds had learnt I was a no-show and had given up on me (sigh of relief). But after researching this post I began to realise how bad this is.

You see in many places greater honeyguides don't indulge in guiding at all. It's believed that this is the result of humans, at some time in the past, welshing on the deal. And increasingly local people are abandoning traditional food gathering techniques (hey, sugar's dirt cheap at the supermarket), leaving the birds high and dry.
Similarly, human activities such as honey gathering are banned in national parks and other protected areas, exacerbating the problem.

So this amazing alliance between bird and mammal - rightly lauded as the world's most impressive example of interspecies mutualism - is rapidly disappearing.

And I'm hastening its loss!



Honeyguides and Honey Gatherers: Interspecific Communication in a Symbiotic Relationship. H. A. Isack & H. U. Reyer. 1989. Science, 243: 1343-1346.

The Fallacy, Fact, and Fate of Guiding Behavior in the Greater Honeyguide. W. R. J. Dean, W. Roy Siegfried & I. A. W. MacDonald. 1990. Conservation Biology, 4: 99-101.