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.

Monday, September 10, 2012

Flipping uncertainties

Yesterday was International Rock Flipping Day.

No, it wasn’t a day of wild celebration for stone-skimming enthusiasts, nor a day of reckoning for designers of rockeries.

On this auspicious day stout-hearted folk from around the globe head out into the wilds to turn over boulders and see what weird and wonderful critters are loitering underneath.

Now each time the event rolls around I’m faced with a quandary. I like the idea of all this collective rock-flipping but quail at the prospect of actually shoving my fingers into the murky haunts of venom-toting beasts.
OK, you may think I’m being overcautious, but the rocks around here harbour 3m (9.5 ft) long black mambas, bad-tempered puff adders and at least two species of cobra (one of whom spits venom with llama-like gusto). It’s a constant fight to keep these creatures out of my home without voluntarily invading theirs!

In the past I’ve deviously circumvented this dilemma (see here and here), but this year my ingenuity failed me and I decided to give Rock Flipping Day a miss. So averting my eyes from all rocks, and trying to ignore the skinks and flat lizards skittering about on every outcrop, I set off to find my mongooses. After one and half hours trudging through the heat, scouring the length and breadth of Koppiekats’ range, I finally found the group sprawled in the shade right beside my car.

And they were lying under rocks.

Although I only had my old point-and-shoot camera with me, I dutifully lay in the dirt on my stomach and tried to take some (bad) under-rock photos.

Whatta you lookin at?

What dwarf mongooses (Helogale parvula) do under rocks.

'There are older and fouler things than orcs in the deep places of the world.'

Rock crevices are ever popular when jackals, honey badgers or dogs pay a call.

OK, I admit I didn’t flip anything. But I also didn’t die a slow and painful death by envenomation.
And I defy anyone to find something cuter under a rock.

To discover what the world's other (genuine) rock-flippers found beneath their rocks, check out Wanderin' Weeta blog.

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