Friday, March 18, 2011

A blessing of bee-eaters

When I first learned what bee-eaters ate I was shocked.

I mean common names are almost always wrong, right?

You don't see honeyeaters plundering bee hives or oystercatchers diving for pearls. An antbird wouldn't be seen dead consuming ants, miners don't venture underground and blacksmith plovers show no interest in metalwork. And as for goatsuckers (nightjars), well...

Anyway, who in their right mind would want to eat bees?

Well, swooping and gliding in the airspace outside my house is a flock of around 10 birds that do precisely that.

They're white-fronted bee-eaters and they just love noshing on stinging things.

White-fronted bee-eaters (Merops bullockoides) always remind me of an Australian aboriginal creation myth that says birds arose when a rainbow shattered and the falling fragments took flight.
Now that's nicer than descending from dinosaurs, isn't it.
Photo by Nathan Rupert.

Looping the loop on slick wings, bee-eaters will snap up other flying critters too (no airborne grasshopper, wasp, cicada or termite is safe) but they actually prefer to feast on bees. Calling to each other with noisy enthusiasm and settling in gregarious clusters on the overhead power lines, they sit scanning the sky for quarry, whimsically tilting their heads to one side and then the other and staring intently straight up into the blue. In Malaysia, olive bee-eaters can spot a 1 cm (0.4") wasp from 80-95 m (260-310 ft) away, and I'm sure my locals are just as astute. Once they detect a victim they dash out in aerial pursuit. Their long curved bill – so like a nectar feeder's – allows them to keep their eye on the ball bee right up to the moment of capture (which is marked with an audible snap). They then zoom back to their perch for a bit of bug-processing.

I love the way my resident clan constantly narrates their activities. They have appealing upward-inflected calls; a tasteful combination of squeaking-door and balloon-rub (I know that doesn't sound pleasant but it is).

Assault and battery. Bee-eaters use violence to de-venom their prey. First they beat the hapless victim senseless and then carefully rub its nether parts against the perch (as you'd move an eraser) to tear away the noxious bits. Photo by Arno & Louise Meintjes.

When I first moved here I was startled to come across what looked like a pile of used Christmas wrappings strewn on the sandy track by the river. As I got closer I realised it was actually a gathering of white-fronted bee-eaters. But 'Oh my God', they'd been massacred!

They were lying perfectly still in a tumbled heap, their wings outspread and their heads, with eyes closed, kinked at horrible neck-broken angles. I stared aghast. Who was responsible for this dreadful carnage? Only when I came within a couple of metres (6 ft) did an eye open, and then another. I could almost hear the exasperated sighs as the sleeping birds slowly struggled to their feet, ruffled their feathers back into place and glared up at me. Oh, they'd been sunning.

But bee-eater weirdness isn't limited to a taste for venom-toting bugs and melodramatic basking behaviour. They burrow too. Yep, they use that constantly-growing beak to gouge out a one metre (3 ft) long tunnel from a cliff face. Their short-legs and tiny feet are specially designed (I'm sounding very creationist today) for earthmoving, with two toes fused partway along their length for improved shovelling power.

Nesting in large colonies, white-fronted bee-eaters can pepper a cliff face with ten burrows per square metre. Their tunnels slope upward - presumably to avoid runoff - but the egg chamber is rimmed with a lip to prevent accidents. Photo by Sander Kuulkers.

My local bee-eaters used to nest in the river bank near my house but they've abandoned the site. You can see why here. The little holes are the original nest tunnels and the big ones are nests excavated by predators. Prime suspects (based on claw-mark size): Nile monitors and honey badgers.

I you haven't already guessed, White-fronted bee-eaters are special. They possess one of the most complex social systems in the avian world. They're like those large, jolly southern European families that feature in Hollywood movies. Pairs team up for life, but they're often helped in their chick-rearing duties by one or two other birds (usually kids who've chosen to loiter at home). While this sort of cooperative breeding is fairly common in birds, white-fronted bee-eaters go even further. Each family unit joins forces with two or three other units to create a big sociable clan (of up to 12 adults). Clan members happily visit one another's nests and forage together, and if one family loses its brood, it will switch to helping raise its neighbour's. But just like feuding Capulets and Montagues, bee-eater clans are intolerant of one another.

Although breeding colonies normally house three to six clans, each one chases rival clan members away from its nests and fiercely defends its own exclusive feeding territory. Since the clan's feeding territory is normally located around 1 km (0.4 miles) from the nesting site, the birds must wing it all the way back each time they want to feed the kids. And this is no mean feat, considering that a bee-eater nestling munches around 50 insects a day (all individually delivered). Phew!

There are currently two other species of bee-eater helping to keep my garden bee-free. The European bee-eaters are migrants, winging in at the start of December for four months of bee-filled R & R. This species is a bit schizophrenic in South Africa. While the ones around here are holidaying after the stress of chick-rearing in southern Europe or the Middle East, those further south are busy stuffing bees into fledglings in preparation for their winter vacation to central Africa.
My third species, the little bee-eater, resides here fulltime. Each year a vociferous pair raises its family in the roof of an old aardvark hole inside one of the mongooses' favourite termite mounds. We've all got used to the scolding.

Bringing home the bacon bee. When breeding a European bee-eater (Merops apiaster) needs to catch around 225 bee-sized insects daily to maintain itself and its chicks. Photo by Joaquim Coelho.

Of the 24 bee-eater species that grace our world, the little bee-eater (Merops pusillus) is the teeniest. It's about the size of a sparrow. Photo posted on Flickr by Lip Kee.
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