Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"

All right, here I have for you something unusual. This is a White-Necked Picathartes, Picathartes gymnocephalus. So you're probably asking, 'what under the blue heavens is a Picathartes?' Well I'm glad you're probably asking that! A picathartes is one of exactly two species of strange birds that live in rainforests of Central and West Africa. The name comes from two combined names … 'Pica' which is a magpie, and 'Cathartes' which is a vulture. So this is a 'magpie-vulture' … except that is not really any of those. They're also called 'rockfowl' and 'bald crows' … again, not being fowl or crows. These birds belong to a unique 'branch' of the family tree of the Passerines or Songbirds/Perching Birds. More about that later. The other picathartes-species, the grey-necked, is similar, but with bright red, blue and black naked skin on its head, while this one's head is yellow and black. The species name 'gymonocephalus' means 'naked-headed', although both species actually have naked heads.

Cliff-Nesters

The two species of picathartes are dependent on a very specific habitat. They need first of all fairly dense and moist jungle to forage in; but for reproduction, they need rocky walls, caves, and/or cliffs with overhangs, underneath which they build their cup-like nests of mud. Most of the rainforest in Africa is in flat, low-lying regions without rocks or cliffs, making them unsuitable for nesting for these birds. There are some hilly and mountainous terrain, in the western part of the rainforest belt, from Sierra Leone eastward, with some good-sized mountains in Nigeria and Cameroon, and from there to about Gabon where there are some eroded hills. The white-necked is found in the western section of this range, and the grey-necked in the eastern parts. Where the rocky cliffs and walls are limited in extent, these birds share them in small colonies. They're most easily seen around their nesting sites; in the forest itself they tend to skulk in the gloom.

The rainforests where these birds breed, are very moist, growth is rampant, and food is available throughout the year. In some parts of the region there are two 'seasons' of even-higher-than-average rainfall, and in these parts the birds may even breed twice per year, in these seasons of abundance. The nests are made of plant fibres, leaves and twigs set in mud and attached to the wall of a cliff or cave or rock, typically protected by an overhang against the near-constant rain. The picathartes pair up, and both parents incubate the eggs and care for the chicks.

Army Ant Followers

These birds are some of several bird species that have come to make use of army ants in the jungle. These are large and aggressive ants that live in huge swarms that practically go to war: they run through the jungle and subdue and kill anything they can. Though this is not quite as bad as often portrayed in popular culture; army ants aren't really capable of overwhelming and killing humans or large animals. But they do manage to overpower many smaller critters, and most importantly for our birds, lots of small things will desperately flee these army ants. So the picathartes (and some other birds) lurk along the sidelines, to try to catch whatever escapes the marauding ants.

When not following the ants, the picathartes will seek their prey in the forest understory, using their bills to probe in the ground or to turn over leaves. They eat insects and invertebrates mainly, but will catch small frogs and lizards. They also will hunt small aquatic animals in shallow water.

Strange Relationships

These birds are unlike any other found in Africa. They are indeed songbirds, members of the Passeriformes, the largest order of birds, which includes thousands of species including such common ones as sparrows, thrushes, warblers, starlings, swallows, larks and many more. As songbirds go, they're fairly large, reaching 40 cm/16" in length. They're somewhat crow-like in shape, but not closely related to crows. For long, they've been believed to be related to babblers, a huge group with many species in Africa and Asia and just a few in the Australian region. Unlike most babblers, though, they are mostly silent, just uttering soft whistles as alarm calls. Indeed, recent genetic studies indicate that they are not babblers at all. They're not closely related to any of the many known families in the songbird order! They are most likely members of a branch that split off from the songbird family tree at around the same point where the oscine songbirds branched into its current two big divisions, the Passerini or sparrow-like ones and the Corvini or crow-like ones.

I speak a lot about relationships in these articles. Remember, when we speak relationships, we're actually meaning 'blood' or family relationships. All of life on Earth is one huge family – we are all related, and going back far enough, a common ancestor can (potentially) be found for any two individual living beings of any species, whether animal, plant, bacteria or anything else. We are related to birds, but very distantly … the common ancestor between mammals and birds likely lived around 300 or more million years ago. Birds are closer relatives of crocodiles … with them, they probably share an ancestor that lived about 240-230 million years ago. Birds are indeed dinosaurs – the small, feathery ones who survived. So in a way, all birds would actually fall into a family or even subfamily of the dinosaurs (most specifically, the raptors), but they very rapidly diverged and speciated, starting around the late Jurassic, 150 million years ago. The main groups of birds living today probably diverged from each other in the Cretaceous, which lasted from 135 to 65 million years ago. I'm not sure about the songbirds, though … they are perhaps the most recent order of birds to evolve, having mainly started taking over the stage from other small birds like the Coraciiforms (kingfishers, rollers, bee-eaters and so on) from around 50-40 million years ago. But they might already have been present, though keeping a low profile, in the late Cretaceous.

The songbirds themselves fall into a few major divisions; the broadbills and their allies are a 'primitive' group of Africa and Asia, with a single outlier (possibly) in South America; the Tyrannii is a group that is mainly found in South America where it is incredibly diverse, containing several families. The Pittas of Africa and Asia are also probably close to these. All of these groups are considered the 'suboscines' or birds somewhat more primitive than the 'advanced' or oscine songbirds. Then there's a group that today is reduced to a tiny remnant, the New Zealand wrens – which are again not wrens, but distant relatives of all of the advanced songbirds. The advanced songbirds then start with the scrub-birds and lyrebirds of Australia, these being considered the most primitive of the advanced songbirds, and from there come all of the rest – larks, swallows, wagtails, bulbuls, shrikes, warblers, real wrens et cetera et cetera. All of these 'et-ceteras' are in turn divided into two big sections: the sparrow-relatives or Passerini and the crow-relatives or Corvini. Both of these groups number in the thousands of species and both are found pretty much all over the world.

So remember when we're speaking of relationships, we're not speaking of outward similarities. That's the thing with species and with evolution: two birds that are very closely related, can be fairly rapidly moulded into forms that look strikingly different, just because they adapted to different lifestyles in different habitats. So you see with Darwin's finches in the Galapagos Islands: from a single rather plain finch-like bird, several new kinds came into origin in a quite short period, with bills ranging from sharp and slender to short and stout. The honeycreepers of Hawaii are an even better example of evolutionary diversity, again having started with probably just a single, finch-like arrival on the islands, which became a huge assemblage of bird species with everything from thick seed-cracking bills to long, curved, nectar-sipping bills, with one species even having evolved a dual-purpose bill with a short, sharp, stout lower bill used to peck holes in bark, and a long, curved upper bill used to probe grubs out of those holes. The Hawaiian honeycreepers between them look like members of several different families, and yet they are all very closely related. (One of the most tragic things in the world is the extinction of most of this fascinating group that has been in progress ever since humans reached Hawaii. Many species disappeared even before Europeans reached the islands, and many more after – it is still going on.)

So when we speak of bird relationships, you need to understand we mean here relationships that can ultimately be traced back to who evolved from whom. To really make sense of the picture, you need to know your birds very well, both in space and in time. Bird fossils are rare, because birds have such thin and fragile bones, but a lot of the movements of birds in time and space can in fact be traced from analysing their relationships and noting where they are now, and how they might have ended up where they are now. The best way we have at present for analysing bird relationships is studying their actual DNA. The DNA is (among other things) a record of changes that were made from one species to another, so species that share more of the DNA are definitely closer related. And the amount of shared DNA can be surprisingly high. We, for example, share about 97% of our genes with chimpanzees.

Furthermore, there are genes that change at fairly steady rates over time, so that they can be used as a 'molecular clock' to show just how far in the past any mutual ancestor of two different species lies. This is not always extremely reliable, but does give a rough guide. This clock for instance seems to show that humans and chimps share an ancestor that lived about six million years ago. Fossils, however, appear to indicate that the common ancestor must have lived somewhat longer ago than that, since we now have found human-like beings that lived six million years and more ago that were already much more similar to us than to chimps. If indeed the mutual ancestor did live six million years ago, then chimps must have subsequently become more ape-like! Which is actually not impossible … evolution can be quite a complex and convoluted phenomenon!

All right! All of that leads us back to Picathartes and its relationships to the rest of the bird world. These two species are indeed now seen as being close to the dividing point between the sparrow-like and the crow-like songbirds. While the latter two groups both number in the thousands of species, there are only two species of Picathartes left. They are thus a kind of link between these two huge groups. These two species today represent a huge chunk of biodiversity and evolutionary history. They are as 'significant' when it comes to how different from other birds they are, as the entirety of the sparrow-ally or the crow-ally assemblages. They once again show how every bit of biodiversity is important … every species is a unique kind of thing, and we should see species as being far more than just individual critters. A species is a vast assemblage of living beings existing in space and over long periods of time, in complex relationships with other species and also with changing environments, representing links, pieces of the puzzle, when it comes to the overall evolution of everything on Earth, ourselves included. Every living species is a link with a past that goes right back to the origin of life on this planet, four billion years ago. Every species is an incredible success story of adaptation and survival, an unbroken line stretching right back to this distant dawn of life, and from there all the way to the present and potentially into the future. How great a tragedy, then, if any of these lines should get broken in our own time – and worse, as a result of our own actions!

Indeed, these two very unique birds are today both threatened with extinction. The rainforests in western Africa are some of those in the world most seriously logged, degraded and fragmentized. There are a few reserves in the range of these birds, but they desperately need more protection. And we still know very little about them … there is much more we still need to learn about their behaviour, ecology and relationships. They need large regions of undisturbed rainforest containing large swarms of army ants, and they need those protective overhangs and caves for building their nests. The latter is perhaps the main constraint on their abundance. If it was up to me, I would build large rock or concrete walls for them with suitable 'eaves' under which they could nest, to help them expand their range!

Colours of Wildlife Archive

Willem

23.01.17 Front Page

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