Tuesday, 2 August 2011

African Vultures

Adult White-backed Vulture in flight - note white under-wing coverts.
So, it's time to return to the savannah I think, and although I've not been out for a while now, I've spent some of the day thinking about vultures, having been reviewing a paper on their distributions. So I thought it would be a good opportunity to think about these overlooked, but rather important birds.
White-headed Vulture, Tarangire, July 2010

Mixed Vultures, white-backed, Ruppell's and Lappet-faced, Manyara Ranch Jan 2011
Let's start by looking at the vultures we get here in East Africa and working out how to identify them. Some, like the above white-headed vulture are always easy - that profile is obvious even in babies. Same goes for the biggest of our East African species, the Lappet-faced, to the right.

But how about the other two common species - Ruppell's Griffon Vulture, and African White-backed? These aren't always so easy. Adults are OK - Ruppell's have pale ends to their feathers, resulting in a scaly look whilst adult white-backed have, well, white backs... But the immatures and (particularly) juveniles are not so easy at times, and if their white-back isn't showing, how do you know? First, you need to decide if it's an adult or not. Look again at the mixed fulture flock on the right here - the second bird from the front has a clear white ruff around the neck - the first bird has a brown one. That's a very good hint that your second bird is an adult. Similarly, look at the birds in the back row and you'll see another white ruff on the bird immediately left of the back-row Lappet. This bird also has a huge pale horn-coloured beak and scales - a typical adult Ruppell's, whilst the second from the front is uniformly pale and has a rather thiner and pointier dark, beak - a typical adult white-backed. So, all is well and good with the adults now you can age them (see the other adult white-backed there?), but what about the juveniles?

White-backed and Ruppell's Vultures squabbling, Manyara Ranch, Jan 2011
This is harder - the Ruppell's only get the scales and pale bill as they get older, but the bill shape is the same. So start by looking at the two adults at the back of the earlier picture to get a handle on bill-shape, and then look at the squabbling birds on the left. The two having a go at each other are obviously Ruppell's (neither is a juvenile, though the bird on the left still has the dark bill and brown ruff so it's obviously immature) and the bird looking right at the front is clearly a White-backed - much thinner beak.

The birds are a little better behaved in the picture below, and you should be able to start getting you eye into those beak differences which are all you've really got (bar size) on the real juveniles. And, of course, if you're in southern Tanzania you're not likely to find Ruppell's at all, though they do wander from time to time. Which means, I'm afraid, that flight identification of juveniles is really, really tricky - I don't think it's possible to be certain all the time.
Feeding Vultures, Ruppell's Griffon and White-backed

The other vulture you're likely to see in Tanzania is the Hooded Vulture, and I can't seem to find any of my own pictures here, but there are plenty of good ones online, and it's not hard to identify - small, thin beak, pink head, etc. And, when I first came to east Africa, you also used to see Egyptian Vultures all the time (again, the adults are easy to identify, black and white plumage with a bright yellow face, though immatures are possibly confusable with Hooded - check the length/shape of the tail (shortish and square = hooded, long and diamond shaped = Egyptian) and the colour of the face (pink = hooded, black or yellow for Egyptian)), but sadly no more - an immature seen in Serengeti and reported to the Tanzania bird atlas recently is the first sign of breeding in the region for a while. Why not, you ask? I have no idea - probably the biggests mystery decline at the moment, so if you've any ideas let us know!

Right, ID sorted, what's to like about vultures? Most people see them as pretty disgusting scavengers, with no redeeming features. But in fact they're very useful - not only do their early morning movements give you a good idea of where the lions might have made a kill, but imagine what happens when you get rid of them. They're incredibly efficient scavengers, known to be more efficient than their mammalian competitors - the flock pictures from Manyara Ranch Conservancy in January were feeding on a wildebeest killed by lions and within 30 minutes had finished the remaining half of the carcas, leaving just bones and a few tatters of skin. Not bad! So, take them away, and their competitors - the jackals, hyaenas and feral dogs will take over, being freed from these highly efficient birds. In fact, this is exactly what has happened in India, where poisoning by Diclofenac killed off nearly all the vultures in just 10 years, with a massive increase in rabies and anthrax too suggested to be caused by the decline of vultures and subsequent increase in mammalian scavengers and uneaten carrion. Not nice, huh? We should be glad of vultures and ensure we reverse African declines too...

How they achieve this efficiency has long been known - foraging vultures keep an eye on each other, and once they find a carcass different species (in general) tackle different bits. Typically the smaller species - white-headed and hooded are the first to arrive at a carcass and they might have a peck at the eyes and other soft parts, but they're not strong enough to rip through the thick skin, so have to attract the attention of larger species. For the thickest skinned carcasses, only the Lappet-faced can cut through, though White-backed and Ruppell's can tackle many. Generally, once the carcass is opened, White-backed and Ruppell's take all the nice soft meat. White-headed and Lappet-faced then come back in and will take all the tough bits - skin and tendons in particular. Finally, the scraps are cleaned up by hooded and Egyptian, with their fine beaks for cleaning around joints, etc. All very efficient, and obviously strongly avoured by evolution because new world vultures (which we now think again are probably raptors, btw), asian vultures and even extinct vulture populations from long ago all seem to have the same three groups.

White-backed Vulture in Baobab, Tarangire, Oct 2009
So, much to be interested in vultures really. And they do make for wonderful sunset shots to leave you with!

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