Showing posts with label birds. Show all posts
Showing posts with label birds. Show all posts

Thursday, January 23, 2014

Oh, the ingratitude

Everyone has days when they feel unappreciated.
You know how it is: those around you not only take your help for granted, they then go on to presume.
Well this is one of those days for me.

What’s caused this sad state of affairs?
Well, with the summer rain, my garden’s transformed into a jungle. The ‘lawn’ has reached head-height and the local avifauna have moved in.
This is not the problem.
I love watching the common waxbills clamber about the tussocks, scissoring off grass seeds with their redder than red bills. Down below the firefinches and blue waxbills hop about searching diligently for windfalls, and garrulous flocks of red-billed queleas swoop in to chatter and squabble among the trembling seed heads.


The joys of being lawn-mowerless
(Common waxbill, Estrilda astrild)

But these little seed eaters aren’t alone. In the wild mango, a pair of scarlet-chested sunbirds are canoodling, and tucked beneath my eaves, four families of white-rumped swifts noisily discuss the pleasures of the day.
But my grievances don’t rest with any of these critters.
It’s the garden’s tiniest feathered bug-eaters that have earned my ire.

Now tawny-flanked prinias aren’t a species you usually notice. They flit about in the undergrowth, pausing now again, with jauntily cocked tails, to peer around for ill-fated bugs. Only if something’s bothering them do you become aware of their loud and persistent complaints: przzt-przzt-przzt.


Tawny-flanked prinias (Prinia subflava) are Africa’s best attempt at a fairywren. However they’re traditionalists at heart, opting for monogamy and nuclear families. This juvenile was photographed by Neil Strickland.

Tawny-flanked prinias were once thought to flutter over much of Africa, India and east Asia (prinia is the Javan name for the species). However, the elegant inhabitants of the orient have recently gained taxonomic independence (becoming Prinia inornata) - presumably to their huge relief (my prinias could never look this refined).
Photo taken in Taiwan and posted on Flickr by John&Fish.

I was sitting on my veranda one morning, with my dogs and cat sprawled around me, when a prinia fluttered down to perch in a tangle of weeds almost at my elbow. Oh how charming, I thought, as I watched it throw out its chest excitedly and clarion its territorial przzts. It then zipped away, returning a moment or two later with a long, wavering grass stem.
Oh no, it couldn’t be...
Surely, not there...
But yes, it was determinedly twining the grass stem around a weed stalk.
I watched aghast: the creature was building a nest at perfect dog nose-height.

Now please bear in mind that while one of my dogs (Wizard) is a dyed-in-the-wool husky who sensibly eschews feathery aperitifs in favour of whale carcasses, the other is a husky-cross. I don’t know what her husky forebear coupled with, but it was certainly purpose-bred to exterminate rodents. Magic’s blood-lust for small defenceless critters is enough to turn even Wizard’s stomach.
I couldn’t decide whether the kamikaze homemakers, busily weaving a nursery just 1.2 m (4 ft) away from us, were the silliest birds to fly God’s airspace... or the most fiendishly cunning.
What snake, what monitor, what raptor would dare attack them there??

The pair dashed back and forth excitedly, hopping up and down on their toes and eagerly entwining leaf blades into their globe-shaped construction. Every now again one (the male?) would alight exuberantly on a weed top and przzt in triumph (just in case some predator hadn’t noticed them). I’m sure birds feel euphoric when they’re nest-building. These two just looked so, well... pleased with themselves.

Hmm, scissor truss joists here I think...

Both Ma and Pa prinia enjoy DIY but since they favour matching outfits (and both don their glad rags for the occasion (brighter with tail extensions)), I don’t know who this is.


The completed nursery.

I was convinced that sooner or later they’d realise the error of their ways and abandon the whole hare-brained scheme, but after a few days three tiny eggs – salmon-brown mottled with purple – appeared inside the rattan ball.

Having borne witness to this folly, I felt obliged to assist the venture. So, for the last month, I’ve been creeping about the garden, calling my dogs away dozens of times a day, dashing outside whenever a harrier hawk or coucal drops by and generally worrying over the hatchlings’ long-term prospects.

Now I do not expect accolades for this effort. I don’t expect the little creatures to sing my praises or bring me gifts (bugs?) or help with the housework. But their actual response left me speechless.

I was busily working on my computer (I do work sometimes) when I noticed a prinia hopping past the back door. I’d seen them flitting about there before and assumed they were hunting bugs. But this one was carrying something in its beak. It hopped on to the back door step, paused, examined the step with its head on one side, looking first to the left and then to the right, and then it carefully put down its burden – placing it meticulously, just so. It then flew off.

Curious, I went to see what it had been doing.
Bad move.
There, right before my door, was a little moist package of bird poop.
And when I looked closely I realised that the whole step was scattered with small white faecal sacs.They were using my door step as a waste dump for their nestlings’ poop!

Now I know that most birds remove (or swallow) their ankle-biters’ droppings so they don’t attract potential chick-munchers.
But why put the stuff on my doorstep?
Do they think my house stinks so badly it will mask the faeces’ odour?
Why not place the goo further along the veranda amid the piles of swift droppings? 
Why not put it, well... ANYWHERE else??

Sigh.
I’m just NOT appreciated.


Yeah, so?

Monday, August 26, 2013

Archaeopteryx meets Priscilla

Ask people to name an iconic African bird and you’ll likely wind up with a whole lake-rim of flamingos and ostriches, plus maybe a ground hornbill or guineafowl thrown in for luck (ahhhhh... splosh).

But of all the myriad feathered critters cluttering the airspace of this continent, there are only two orders who flutter here and nowhere else: the mousebirds and the turacos.

I’ve already sung the praises of cute little mousebirds, so today I’ll take you down to the river to meet one of the weirdest birds I know.
A creature of the forest, around here it lives only in the verdant tangle of trees along the riverbank.  As you pass beneath the towering leadwoods, jackal berries and figs, you’ll hear its eerie kok-kok-kok-kok-kok call (which rises, in strength and pitch, to a deafening crescendo) reverberate through the gloom (you can also experience it here).
Carefully scan the smooth upper branches of that giant fig... but no...
Wait... there!
In that water berry, there’s movement.
A large ungainly bird suddenly lopes out along a branch, swaying slightly from side to side as it runs towards you. At first it looks to be black, its long wedge-shaped tail dark against the sky, but as it paces through a splash of sunlight you see its flamboyant plumage: iridescent purples and greens with a flush of rose rising on its breast. Without pausing stride, it leaps over a gap and halts abruptly on a branch directly above you. For a moment it shifts uncertainly from foot to foot, craning first left, then right, trying to catch sight of you. Then, cocking its head on one side, it peers down with one carmine-encircled eye, raising its raffish violet crest (a movement suggestive of arching an eyebrow) and fixes you with a fierce quizzical glower.

This is the purple-crested turaco.

If it decides you’re scary enough, you’re in for a real treat.
After a moment of dithering, running and hopping, it opens its stubby, rounded wings to unfurl a dazzling pageant of scarlet. It then launches into an elegant, balletic leap and glides away to a nearby tree. (I couldn’t find an ‘available-for-use’ image of the bird in flight - and of course snapping one is way beyond me - but please take a look at this one; it’s worth it.)


Running through the treetops, the purple-crested turaco (Gallirex porphyreolopha) bears a distressing resemblance to the world’s earliest feathered aviators.

Young turacos (this one’s an up-and-coming Ross’s turaco) even bear gnarly claws on their wing joints (used for pre-flight travel). They sensibly lose these primordial mementos in the embarrassment of adolescence. Photo posted on Flickr by SeaworldSA.
 
The turacos’ proficiency at tree-clambering is aided and abetted by a weird, reversible outer toe. This accessory normally sits at right angles to the axis of the foot, but can be swivelled fore or aft, depending on need. Photo by Vince Smith.
 
Turacos are members of an ancient order (Musophagiformes) and - since they keep themselves to themselves - no one really knows who their relatives are. The proteins in their eye-lenses (hey, the first place you’d look, really) hint at kinship with songbirds, their feather parasites are cousins to those on itchy fowls and their strange, swivel toes place cuckoos in their ancestry.
But as far as I’m concerned, they’re like no other. There’s something absurd and incongruous about their awkward, cumbersome shape coupled with such over-the-top plumage. They somehow remind me of avian drag queens, and I’m always half expecting them to break into an Abba dance routine.
Of course, it’s entirely inappropriate to question the purple-cresteds’ sexual predilections: they’re highly conventional birds. Living in old-school nuclear families, they’re unflinchingly monogamous and defend their home turf (very noisily) from anyone who may disrupt their conservative familial bliss.


I included these dreadful images (typical of my photographic prowess) because they show (in a blurry way) courtship feeding. It sounds so romantic, doesn’t it? Then you realise he’s hacking up regurgitated fruit pulp...
 
Nevertheless she seems grateful. Maybe it’s because she knows there’s worse to come. Parent turacos not only chomp their little darlings’ old eggshells, they gulp down their excrement too.

Now if turacos are the closet transvestites of the avian world, it’s the way they come up with their extravagant costumes that’s earned them global notoriety. You see turacos are the only feathered critters able to wear green. Lesser birds may look green but it’s all a con. While others achieve their verdant hues using yellow feathers (structured to refract sunlight and reflect blue wave lengths), turacos manufacture a genuine green pigment, turacoverd. This unique colorant is a copper uroporphyrin compound made up of 6% copper. The birds’ brilliant red wing feathers (found in most of the forest-dwelling species) are also designer-made, tinted with another exclusive copper-based stain, turacin. (The rest of the world’s birds must make do with carotenoids, for bright, orangey reds, and phaeomelanins, for rusty reds). But accumulating so much copper is challenging (so that’s who’s stealing the telephone cables...) and it takes young turacos twelve months to grow as gaudy as their parents (cable theft is slow work?). It’s even been suggested that turacos are only able to employ copper-based pigments because they dwell in one of the world’s richest copper belts.

 
The local copper Mecca: humans have been mining the stuff around here for more than 1200 years. This is the Phalaborwa copper mine, about 60 km (37 miles) up the road.
 Photo by Roman Betik.


Pride of the kingdom. The purple-crested turaco (Gallirex porphyreolopha) is Swaziland’s national bird. But fame and fortune come at a cost: the species’ dazzling flight feathers feature prominently in the ceremonial regalia of the Swazi and Zulu royal families.
Photo by Lip Kee.
 
Of course turacos are not alone in using copper to brighten up their world. Humans have been daubing this metal about ever since those old winos, the ancient Greeks, discovered how to cook up verdigris (expose copper plates to the fumes of fermenting grapes, then scrape off the crust of blue-green tarnish). Unfortunately humankind subsequently went astray (oh, that’s unusual) creating killer wallpaper throughout the 19thC using a copper-arsenic dye (Napoleon’s emerald walls probably hastened his demise: studies show his hair samples are chockfull of arsenic).
Sadly, this pigment was also used to tint clothing, sweets and deserts. A mass poisoning in Greennock, Scotland (where green confectionary was all the go during village celebrations) spawned a national aversion to green sweets (and I’ve indeed met a Sparkle-scoffing Scot who staunchly refused the green ones). Nevertheless, it’s all OK. Once our forebears figured out the perils of snacking on arsenic they converted their lovely green dye into an insecticide...


There are 23 species of turaco (all native to deepest, darkest Africa) and I couldn’t resist showing you how spiffy they are. This demur little one is a Knysna turaco (Tauraco corythax) from, well, Knysna in South Africa. Photo by Johann du Preez.
 

“What do you mean, you’ve never HEARD of turacos!”
Photo (of a white-cheeked turaco, Tauraco leucotis) by Loren Sztager.
 

Like all turacos, the red-crested (Tauraco erythrolophus) from Angola likes to munch fruit, flowers and buds. They’re such committed fruitarians that they even feed their chicks mostly just fruit pulp. Photo by Ciaran Dunston.
 
Turacos once laboured under the name of plantain-eaters until ornithologists realised they didn’t. This one’s a great blue turaco (Corythaeola cristata) at home in the Congo jungle.
Photo by Brent Moore.


As well as the brightly coloured forest species, there are a few drab turacos who knock about in open woodland (the unfortunately named go-away-birds). But what these species lack in garishness they make up for in behavioural peculiarities. The grey go-away-bird (Corythaixoides concolor), who lives around here, often breeds in cooperative groups.
Photo by Arno Meintjes.

 
Livingston’s turaco, I presume (Tauraco livingstoni). This species explores the forests of southern Tanzania and Malawi. Photo by Heather Paul.
 

Ross’s turaco (Musophaga rossae) ready for the mardi gras. Longevity is one of the turaco's many claims to fame with captive ones surviving more than 30 years.
Photo posted on Flickr by San Diego shooter.
 

 
The Hartlaub’s turaco (Tauraco hartlaubi) leaps about in the forests of the Kenyan highlands.
Photo by Francesco Veronesi.
 
“Mama mia, here we go again... my, my... how can I resist you?” 
Photo posted on Flickr by Belgianchocolate.
 

Sunday, September 23, 2012

Male nannies get the girls

One of the advantages of living above the river is the endless aeronautics display.

Step outside my door and you're treated to fork-tailed drongos fluttering and plunging, little bee-eaters, adorned in cinnamon and gold, effortlessly looping the looping and, way up above, tiny swifts floating like calligraphy bewitched from the page.

But among these master aviators, there’s one creature that surpasses them all.

Dressed like an accountant and encumbered by a massive ice-pick bill, it seems an unlikely candidate for aerial supremacy, but the pied kingfisher is utterly mesmerising.

Zooming along just inches above the water, it suddenly rockets upward 10m (33ft) into the air, and there it stalls. Completely. With its torso held almost vertically and its huge black bill pointing straight down, it hovers motionless; not just for a few moments, but on and on and on.


Pied kingfishers (Ceryle rudis) are the second largest of South Africa’s ten kingfisher species. This one’s double necklace of black reveals that it’s male; females are more demur, sporting only a single band. Photo posted on Flickr by Tarique Sani.

It’s at this point that I start feeling anxious. I know I should be excited at the prospect of the hunt, and I’ve seen other people clutch one another eagerly and cry, “Oh look, it’s about to dive!”
But as the bird just hangs there, flouting gravity, I find myself glancing at the pool below and wondering how anything can plunge at breakneck speed into one foot of water without suffering... er, neck-breaking consequences. As the bird continues to hover (for the next 5 to 10 seconds), pictures drift into my mind: murky underwater images of kingfishers stuck bill-first in the muddy pond floor.

Of course this never happens. Down the bird plummets, plunging below the surface and immediately surging back up - almost at the same speed (how does it do this?) - amid a glittering cowl of water droplets.


Pied kingfishers plunge-dive in waters throughout Africa, India, Myanmar and southern China. While African birds dine exclusively on fish, those living in Asia are less fussy, enjoying side dishes of aquatic insects and crabs.
Photo by Arno Meintjes.

But if the way pied kingfishers acquire lunch is bizarre, it’s nothing to the way they produce more little kingfishers.

Defying all kingfisherly conventions, this bird thumbs its nose wings its beak at the concept of territoriality.
And nuclear families? Well, who needs ‘em?

You see unlike other kingfishers, pieds gather together in busy breeding colonies. Using nothing but beak and claw, they gouge out 2 m (6.6 ft) long nesting tunnels in a communal bank, sometimes crowding their homes to within 0.5 m (1.6 ft) of one another.
And as if this isn’t social enough, loving couples also share their underground hideaways with up to six male nannies!


Born to burrow. The pied kingfisher's second and third toes are partly fused together; this is thought to help them shovel dirt.
Photo posted on Flickr by skuarua.

So how does all this come about?
Well, young pied kingfishers leave the family home normally at about four months of age, but if the guys don’t find themselves a girl (and 95% bomb out), they move back home with Mum and Dad. Now this isn’t as bad as it sounds because they do help out about the house. In fact, they put as much effort into their chores (guarding the chicks from marauding mongooses, monitors and rivals, and ferrying fish to them) as do Mum and Dad. Of course this is sensible (and so isn't the kind of behaviour you expect from young males): if you can’t have kids of your own, at least you can give your genes a push-start by helping your little brothers and sisters.

However, in some pied kingfisher colonies, pairs also take on unrelated childcare workers.

But why do these males want to hand over good fish to strangers?
And if there’s free help available, why don’t all colonies take advantage of it?
To get to the bottom of this fishy behaviour (sorry), Uli Reyer undertook a long-term study in Kenya, comparing kingfishers that lived on the windy shores of Lake Victoria (where non-related home-help is all the go) with those dwelling at flamingo-rimmed Lake Naivasha (where it’s unheard of).

He found that if you’re a pied kingfisher, Lake Naivasha is the place to be. Here the birds live a cushy life, feasting on plump native cichlids. Even without any help, pairs are able to successfully rear four healthy chicks.
But things are very different at Lake Victoria. The kingfishers here dine on slim, deep-water sardines which only come up to the surface at dawn and dusk. The birds must fly long distances over open water to reach their feeding ground water and the wind-whipped ripples reduce visibility. Only 24% of the birds’ dives snare a fish (compared with 79% at Naivasha), and pairs working alone can raise only 1.9 chicks. Half their hatchlings simply starve to death. So Lake Victoria kingfishers needed all the help they can get.


A juvenile pied kingfisher (and groups normally rear four) gulps down 35 g (1.2 oz) of fish daily and is fed for at least six weeks. But the fish the kingfishers catch average only 1-2 g (0.04-0.07 oz). Even without a calculator, that’s an awful lot of work!
Photo posted on Flickr by Lip Kee.

Just to make certain that it was the need to put food on the table that led to the recruitment of helpers, the researchers sneakily increased the workload of Lake Navaisha pairs by doubling their clutch to 8 to 10 chicks. Sure enough, these beleaguered parents happily accepted non-related nannies into their homes, even though this was not the done thing in their neighbourhood. In contrast, when families at Lake Victoria were reduced to just one or two chicks, the unburdened parents steadfastly rejected the approaches of potential helpers.

But all this doesn’t explain why unrelated males want to help.
If they don’t have younger siblings to care for, why don’t they just loaf about, marshalling their resources so they’re super sleek and sexy for the next breeding season?

Well Reyer discovered that 91% of these unrelated, live-in childcare workers landed themselves a girl the following year (compared with only 60% of the stay-at-home sons and 33% of the loafers).
What was their secret?
Well, almost half of these successful Lotharios teamed up with the female they’d helped the previous year!
You see fathering baby kingfishers really takes it out of you, and only about half of dads survive to breed the following year. And when hubby passes on, who’s right there, offering a consoling fish to the grieving widow? The live-in help, of course.

Unlike sons stuck at home (whose testes don’t even bother to produce sperm), unrelated helpers are all primed up for sex. This explains why Dad only accepts them into his family after his chicks hatch out and there's no chance of a bit of hanky-panky with Mum.
Photo by Andy Li. 


In fact, it looks as if the pied kingfishers’ unique nesting colonies actually serve as old time hiring fairs. Here, amid all the hustle and bustle, youths seeking childcare work can check out prospective families and advertise their availability (by presenting Dad with a gift of fish), and overworked parents can pick and choose whom they’d like to have help with the kids.


Looking smug? Traditionally kingfishers are associated with good luck. Photo by Martin Heigan.



Friday, February 3, 2012

Masked weavers revealed

If you’ve come here expecting an exposé on the criminal activities of textile workers, you’re in for a disappointment.

This post is about something much less exciting: SEX.

Now I don’t know how you choose your sexual partners, and I wouldn’t dare suggest that anything is inappropriate... But whatever traits turn you on, you can be certain that somewhere out there someone with feathers is already doing it.

Regardless of whether your interest is sparked by a lover’s apparel, their talent in the performing arts, their real-estate holdings, the colour of their footwear (you’d have to be a real booby to go for this), their artistry or – let’s get down to it – the size of their gender-specific endowments (excuse me, I was referring to tail plumes), your tastes don’t differ from millions of birds.

But there’s one group of feathered critters whose predilections are genuinely perverse.
For them, sweaty singlets and wolf-whistles are all the go.
That’s right; construction workers rule the roost in weaver society.

Now if DIY skills were the currency of ardour in humans, I’d be destined for barren spinsterhood (hey, wait a minute, I am a barren spinster...). Although home-building skills may seem a tepid way to woo a lover, it hasn't held back weavers. Around 62 species (all in the genus Ploceus) are out there busily knocking up their edifices, mostly in Africa but also in southern Asia too.
And with all the recent rain, a large proportion of these creatures seem to be doing it right here.


A macho lesser masked weaver (Ploceus intermedius) kitted out for love. He only dons his mask - in bad-boy warning colours - when the talent weather is hot.

Gathering in rowdy hordes in trees overhanging water, the local lesser masked weavers are in a state of frenzy.
Males dash back and forth with long grass stems trailing from their bills, and there’s a constant buzz of chirping and squawking, which swells periodically into a goal-score roar when a flirtatious chick drops by.

Before a weaver on the make can fabricate an alluring boudoir, he must first stake out his own patch within the colony. This involves lunging at intruders and grappling tooth and nail beak and talon with any persistent rivals. Once he's scored an exclusive building site, Romeo gets to work weaving a collection of finely-laced, retort-shaped homes (if you're not a closet alchemist, a retort is a glass flask with a spherical base and a long tapering neck that's bent downward; it’s designed for distilling things). The male’s goal is to distil a harem of lady tenants who’ll considerately raise his chicks for him.

Using only fresh green grass, plucked straight from the clump, he twists and pokes and pulls, entwining the strips intricately, while emanating an air of intense and bad-tempered concentration. As the grass strands dry, they shrink, tightening up the weave and strengthening the structure. But with nest sites at a premium, a male can’t afford to keep any untenanted premises on his books, so pissed-off males demolish nests that have proven unpopular.

In the quest for the most beguiling nest, males also indulge in a bit of landscape gardening, clipping the leaves from all branches near their homespun abodes. This - along with the nest’s funnel entrance - is thought to make things tricky for those iniquitous nest robbers, the harrier hawk and the boomslang.


‘These damn things just keep growing BACK!’



‘Well, that’s an improvement anyway.’


When a lady weaver approaches, all the males get very excited, snatching up a grass stem and dashing to their best construction. Hanging from the base, a hopeful male flutters his wings enticingly, sticks his tail out horizontally and points his beak suggestively into his nest. He also chirps in a frenzied manner (precise translation unavailable, but I daresay you know all the usual pick up lines...).


‘If you come in here, you can see the playroom has a northerly aspect...’


‘I think someone should really tell George that the can-can is so yesterday.’


For any inept handymen out there, consoling themselves that bird's nest-building skills are hardwired anyhow, let me disabuse you. Male weavers must learn their trade.

While yearling females rush headlong into motherhood, their brothers eschew sex for a year or two. These young bloods get together in colonies of their own where they can work on their erections without censure. Experiments show that if adolescent males are deprived of this early practice (by denying them building materials), their DIY skills are seriously retarded. However, just like riding a bicycle (which you may be please to know male weavers cannot do), building prowess - once learned - is never forgotten; even if callous researchers blockade building supplies for years on end.


Slipshod workmanship will not escape the eye of a lady lesser masked weaver. However, the landlord's only responsible for creating the nest’s outer walls; all soft furnishings must be provided by the tenant.

But what does today’s lady weaver seek in a family residence?

Researchers working with village weavers (Ploceus cucullata) found that mothers-to-be aren’t swayed by outward appearances; neatness and closeness of weave are, after all, mere superficialities. What counts is the strength of the materials and the newness of construction. The girls will have no brook with old, browned off nests and, like master chefs, they’re canny at detecting what’s fresh and what’s not. Merely painting a good nest brown will not fool them, although the same cannot be said for males, who are three-times more like to demolish a nest if it’s been artificially dyed brown.


‘Hmm, I do like a Paspalum veneer; it gives a much fresher ambience than the traditional Poa finish...’



‘Yes Martha, I’ll join you in a mo’. That little minx Estella is looking real interested in Number 3.’



Tuesday, December 13, 2011

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.




Saturday, September 10, 2011

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.
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