Ratites; the ancients of the bird world. #2 The case of the flying moas

In introducing the wonderful and venerable ratites last time I made mention of another group of relatively little-known birds, the tinamous, long described as a 'sister group' of the ratites. There are 47 species of them in South, Central and North America, as far north as about central Mexico. Like the ratites they are Palaeognaths, forming with them an entirely different group of  birds, the 'ancient palates'. They fly poorly but can still do so and, unlike the ratites, thus retain the keel on the breast for anchoring the mighty flight muscles. They also differ from the ratites in having powder down feathers - amazing feathers which are never moulted, but which crumble at the tip to provide a permanent supply of conditioning powder (sort of like home-made talc) for cleaning and generally improving the feathers. For these reasons it has always been assumed that they separated from the ratites early in the piece, but travelled with the rheas when South America broke free of Gondwana. This means too that they couldn't actually be ratites, because that would imply that they had a common flightless ancestor with the rheas and regained flight in South America - such a reversal of all the acquired adaptations to a flightless lifestyle is universally regarded as an evolutionary impossibility.

Tinamous are notoriously shy, and to date I've only seen three species - all rainforest birds - two of them at one sitting, courtesy of the wonderful Aguas Verdes initiative in northern Peru, where forest birds are lured to a hide by offerings of corn. As a result the forest has been spared from conversion to coffee, and other landowners are taking interest; more on this story here. 

Cinereous Tinamou Crypturellus cinereus, Aguas Verdes, lower eastern Andes slopes, northern Peru.
This shows typical tinamou characteristics - strong running legs, and virtual lack of a tail,
which is associated with their reluctance to fly, and general lack of competence at it.
This is a medium-sized tinamou, weighing about half a kilogram.

The Little Tinamou Crypturellus soui is indeed one of the smaller tinamous,
weighing only 200-250 grams.

Tinamous, as I mentioned, are very hard to see normally, and this cryptic behaviour has saved them to some extent from dramatic losses suffered by other largish edible birds in their range. Nonetheless hunting pressures can be severe, along with steady habitat loss.

Great Tinamou Tinamus major at roost, Napo Lodge, Ecuadorian Amazonia.
This is a species that is facing problems, having been recently listed as Near Threatened.
It is a big tinamou, weighing well over a kilogram.

OK, you've been very patient - if indeed you're still reading! - while I go on about a group of birds that aren't really ratites. However, that's only what we used to think... I've been at some pains to introduce them because new understandings about them have changed pretty much everything we now think about ratites too. The nice neat story about ratites representing the archetypal Gondwanan story - an ancient group which inhabited all the southern lands before they parted ways, and drifted with the new continents to their new positions, was very appealing and was one I've told, in all good faith, many times over the years.

There have been some mutterings over the years along the lines of "OK, they're old, but not quite that old!". The mutterers had some good points - for instance Africa broke free of Gondwana by at least 110 million years ago. Madagascar was isolated by 88 million years ago – but from India rather than Africa! But still, how else could we explain what we see? Then in 2010 a paper was published by a group of Australian and New Zealand scientists which turned this particular comfortable understanding of the world inside out. They had available to them techniques denied to earlier researchers, including the ability to do a complete mitochondrial DNA analysis (mitochondria contain far less DNA than do cell nuclei, and this DNA seems to evolve more quickly than does that of the nucleus so tells good stories) and to look at such material from fossils.

The technique has rapidly become widely used to study a range of animal groups, comparing species to determine when their Most Recent Common Ancestor walked the earth ('MRCA' appears all over the place now). Phillips et al shocked us all by announcing that far from being associates of the ratites, tinamous are slap bang in the middle of them - they are ratites for any practical purposes. One existing hint (isn't hindsight wonderful?!) might have been that tinamous, like most other ratites, breed most unconventionally - a male waits to be visited by groups of roaming females who mate with him and lay their eggs into his nest, then move on and find another obliging dad for their eggs. (There are a few tinamou variations, but this is the norm.) It is generally regarded as a very efficient way of rapidly increasing populations.

Darwin's Rhea father and chicks - who between them have many mums - Torres del Paine NP, Chilean Patagonia.

From the conventional viewpoint however it gets worse - the closest relative of tinamous are not the obvious rheas, but the New Zealand moas! Moreover the same study showed that Ostriches and the recently extinct Madagascan elephant birds are not each other's closest relations, as logic would insist, but the elephant birds and kiwis are closer to each other than they are to anyone else... Ostriches are way out on the ratite fringes - and may have even arisen in Eurasia, arriving in Africa only some 23 million years ago.

The only way to make any kind of sense out of all this is to accept the seemingly preposterous idea that the ancestral ratites flew to their current continents, then all (except for the tinamous) subsequently lost the power of flight. Kiwis and emus/cassowaries parted ways only 60 million years ago - but by then New Zealand had been isolated for 20 million years. Moas and tinamous separated at about the same time.

It's a difficult concept to absorb. I've always been a firm believer in the parsimony principle – ie that the simplest evidence-based explanation is always likely to be the correct one. The more evolutionary steps that are required to explain something, the less likely it is that it happened that way. But once we accept, however reluctantly, all this explosive material, how on earth are we - or at least the researchers - supposed to explain such a bizarrely unlikely set of circumstances? What could possibly have happened right across the Southern Hemisphere to have triggered a series of wildly unlikely parallel events at about the same time?

Well, of course something did. Around 65 million years ago, already a time of colossal volcanic activity, a massive meteorite, an asteroid some 10km across, smashed into what is now the Yucatán Peninsula of Mexico, hurling vast quantities of dust and smoke into the atmosphere and dropping temperatures cataclysmically. Sulphates hurled into the air formed nucleation sites for brutal acid rain storms. Once the dust particles settled the huge quantities of carbon dioxide released raised worldwide temperatures for centuries. By the time things had started to settle down again, three quarters of all plant and animal species on earth had vanished, including all the dinosaurs (other than some of the birds of course). 

Southern Cassowaries, Etty Bay, North Queensland.
Their small flying ancestors survived the great meteorite strike.

It was an empty landscape, full of menace and opportunities. Among the now-empty niches was that formerly occupied by the birds' immediate ancestors, the erect running dromaeosours. We know that birds, especially on islands, are prone to give up the enormously energy-demanding flight habit when there is no longer a pressing need for it. So, it is not at all hard to conceive that members of a particular group of bird survivors, with the genes of the dromaeosaurs still within them, should have responded to landscapes suddenly largely devoid of predators and full of options, by giving up flight that had carried their ancestors across the oceans. Later they also grew larger in response to such predators that did eventually arise.

Darwin's Rhea chicks, Patagonia.
Their ancestors flew to South America, arriving quite separately from the (apparently later) tinamous.

An unlikely story, but the only one that fits the facts - and the job of science, and indeed of common sense, is to find theories to fit the facts, rather than deny the facts to fit a theory.

And doesn't it make a good story?!

PLEASE REMEMBER THAT I ALWAYS VALUE YOUR COMMENTS!
THEY CAN BE ANONYMOUS (THOUGH OF COURSE I'D PREFER TO BE
ABLE TO THANK YOU BY NAME) AND YOU DON'T NEED A GOOGLE OR ANY OTHER ACCOUNT.

BACK ON THURSDAY
 (And remember that you can get a reminder when the next post appears by putting your email address in the Follow by Email box in the top right of this screen.)

Ratites; the ancients of the bird world. #1 Who are they?

Across the southern lands are (and in some cases were) scattered a series of mostly giant, flightless birds, whose significance we often overlook. We call them the ratites, from Latin for a raft, a reference to the flat breastbone - if you no longer fly, you no longer need either the great flight muscles (some 15% of your bodyweight) or the keel on your breastbone to anchor them. 

Emus Dromaius novaehollandiae near Esperance, Western Australia.

Their significance in the world of birds is their undisputed role as The Elders. The most fundamental subdivision of the world of birds is not, as one might expect, into Passerines and Non-passerines, but into the Palaeognaths (the 'ancient palates') and the Neognaths ('new palates'). The details of the palates needn't concern us here, but the elemental subdivision thus created certainly does, because the Palaeognaths comprise just the ratites and their associated 'sister group' the South American tinamous (but more on them later). It's just them versus every other living bird!

Since we've started this introduction to them in Australia, we might as well continue here. When Europeans arrived here there were probably three species of emus. The small emus on Kangaroo Island (off the coast of South Australia) and King Island (in Bass Strait between the mainland and Tasmania) are generally regarded as separate species (D. baudinianus and D. ater respectively), but the evidence is tragically limited, with only one and three skins respectively surviving. Some authorities take a more cautious approach and regard them as sub-species. There were also Tasmanian Emus which were almost certainly the same species as the mainland birds; they were gone by the 1860s, while the other two were exterminated horrifically soon after the arrival of Europeans in the early decades of the century.

Kangaroo Island Emus, by French self-taught natural history artist Charles-Alexandre Lesueur, who
sailed with the Baudin expedition of 1800-1803. While visiting Kangaroo Island they captured two
unfortunate emus and took them back to France.

On the mainland they're still doing well, though they retreat from settlement and are now very rare in the south-eastern highlands. I'll talk more about Emus than the others, both because I know them best, and because much of the information about them can be used to compare the others.

Emus on the Hay Plain, south-western New South Wales.

They are found across all of inland Australia, where they are nomadic, following the rains and feeding on seeds or fruits or caterpillars or grasshoppers as conditions dictate. This nomadism and their disdain for fences has led to many of their problems with European settlement. In Western Australia the 'Great Emu War' of 1932 was fought between migrating mobs of over 20,000 emus, and the Australian army with machine guns and grenades, called in by the WA government. Jock Marshall in his pioneering conservation work The Great Extermination (published in 1966, just before he died, far too young) reports "History does not record the name of the CO emus, but he must have been a good chap". It seems that perhaps only a dozen emus were killed, and the government had to withdraw the military to save them from further embarrassment.

Like most ratites, Emus are polyandrous, though they start off the breeding cycle as a pair in mid-summer, and dally for about five months. In late May and June she lays up to 20 large dark green eggs in a scrape on the ground, totalling up to 15kg. Not surprisingly, she reckons by now that enough is enough, and she plays no further part in the process, though if she’s still feeling frisky she can go off and do it all again with someone else! Each time she leaves the father in sole charge. He broods for eight weeks, and during the whole time he lives off his body reserves without eating, drinking or defecating, rousing only to turn the eggs several times daily. In this part of the world eggs were apparently laid in about July, which meant that the male was incubating in the snow.

Emu eggs, north-western New South Wales.

In South America rheas are even more Bohemian (from a very anthropomorphic perspective!). The texts tell us that “males are simultaneously polygynous, females are serially polyandrous”, which means that males become territorial, while females form small mobile groups which roam around seeking collective dalliance with likely-liking blokes. He mates with the group of females who all lay eggs in his nest, then go off to look for another bloke to do it all again.  

Darwin's Rhea Rhea pennata and chicks, Torres del Paine NP, Chilean Patagonia.

Kiwis on the other hand are always monogamous, while ostriches can be monogamous in harsh desert situations, though their usual approach is much more complex. A dominant male and female share brooding duties, while in the same territories subordinate females mate with multiple subordinate males and leave them to get on with, as with the emus. At the same time roaming males pass through and mate with the females, but it's not clear who ends up holding the baby in that situation.

The striped Emu chicks can walk within hours, and run and swim within a week. As they get older, they are distinguished from older birds by a dark neck and head. Dad cares for them for 18 months, so he only breeds every other year.

Emu with young chicks near Cue, inland Western Australia.

Father and older chicks, northern Flinders Ranges, South Australia.

All more modern birds have feathers which 'zip together' by tiny hooks on the barbules along the edge of each barb, hundred of which branch from the central vane, or rachis. In ratites these hooks are missing, so the plumage is much looser and more hair-like than we're accustomed to seeing in a bird. An Emu can be somewhat reminiscent of a haystack in fact.

Shaggy Emu plumage.

Something else is happening here too though. Some birds, especially more primitive ones, have an aftershaft, like a small second feather, branching from the base of their feathers; passerines mostly lack them. They tend to be woolly and it seems as though their purpose is primarily insulation. In Emus however this aftershaft is the same length as the main shaft, and in fact it is generally not clear which is which. You may get a sense of it in the photo above, but here's a single Emu feather. They share this oddity with cassowaries, which are in the same family.

Emu feather; the aftershaft is as long as the main shaft.

In kiwis and cassowaries, the plumage is much coarser and hairlike, probably for waterproofing, at least on the exterior; the underfeathers tend to be woolly.

Southern Cassowary Casuarius casuarius, Etty Bay, north Queensland.

One more thing on Emu plumage; they have a somewhat curious 'part' down the back, with the feathers falling away on either side of it.

Emu drinking near Esperance, Western Australia; note the conspicuous part along the spine.

All ratites have three toes, except for ostriches, which have reduced that to two. All except the forest-dwelling kiwis and cassowaries are birds of the open plains, and all except kiwis are runners. All of these can easily maintain speeds of 50kph, and the smaller rheas up to 60kph; an ostrich when pressed however can reach 70kph. 

Emus and cassowaries are in the same family, but the other groups each form their own family. There are three species of cassowary, all found in New Guinea, while the Southern Cassowary is also found in the rainforests of north Queensland, to where it doubtless walked during a glacial period when Torres Strait was dry - this last happened only 10,000 years ago. Their most obvious characteristic is the tough flexible casque on their head, whose purpose is still debated. It was supposed that it helped in running through dense vegetation, but there is no evidence for that. Captive birds have been observed using it to shovel litter aside, and it probably also has a display purpose, along with the colourful neck wattles.

Southern Cassowary, Mount Hypipamee NP, north Queensland.

Cassowaries are primarily fruit-eaters and are important vectors of rainforest fruit seeds. It has very recently been shown that the seeds of the Javan Ash Ryparosa javanica, a rainforest tree from north Queensland, germinate far better if fed first to a cassowary. In fact, over 90% of seeds taken from cassowary droppings germinated, compared with only 4% of uneaten seeds. Javan Ash seeds incidentally have one of the highest levels of cyanogens ever recorded in a plant, but presumably the birds pass them through quickly enough and without breaking the surface of the seed, so that they are unaffected.

In Africa there are two ostrich species, as the result of a recent recognition that the Somali Ostrich of far north-east Africa is a separate species, Struthio molybdophanes, from the much more widespread Common Ostrich S. camelus.  They are the world's largest birds, males standing up to 2.75 metres tall and weighing close to 150kg. Unlike other ratites males and females are very different; males are far larger, but are also black and white, compared with the females' duller grey-brown tones. 

Male Common Ostrich, West Cape NP, South Africa.

There are five species of New Zealand kiwis, relatively small forest-dwellers with characteristic long down-curved bills and highly developed senses of smell for finding worms and arthropods in soil. They are primarily nocturnal, though this may be only since the advent of humans and associated predators. They form a life-long pair bond; a kiwi's egg may be 25% of its body weight, making it the largest of any bird.

North Island Brown Kiwi Apteryx mantelli;
photo courtesy Wikipedia.

In South America there are three species of rheas, though until recently only two were recognised. Rhea was the mother of the classical Greek gods and goddesses, but we have no idea why Paul Mohring, the German biologist, applied the name as a genus in about 1750. While brooding, the male is very aggressive, to the point that once he’s started brooding further females laying eggs must leave them outside the nest, and leave him to pull them in. Their food focus is on broad-leafed plants, but they also eat seeds, roots, fruit, insects, and small vertebrates. As ratites go they are relatively small, only a metre tall and with relatively long wings; this enables their very impressive turn of speed.

Darwin's Rhea Rhea pennata and chick with Guanaco (which gives an idea of how relatively small the bird is)
Torres del Paine NP, southern Chile.

Darwin's Rheas near Punta Arenas, on the Strait of Magellan, above and below.

There were apparently seven or eight of the mighty elephant birds of Madagascar, in two genera; the largest of them stood three metres tall and weighed up to half a tonne. They survived until recent times, until the arrival of humans, who presumably hunted them and their eggs to extinction. They were certainly present within the last 1000 years, and there are accounts attributable to them much more recently than that. 

The same sad tale could be told of the nine New Zealand moa species, the largest of them standing a colossal 3.6 metres high and weighing close to 250kg. Unlike all other ratites they had lost even their vestigial wings; presumably as forest-dwellers they were not runners and had no need of them for balance. They disappeared only some 600 years, overhunted by the newly arrived humans.

The conventional story of ratites is that they are a classic example of old Gondwanans, scattered across the southern lands as the continents took them on their journeys. That is the story I want to examine next week - be prepared for surprises if you've not hitherto heard this one!

BACK ON THURSDAY
 (And remember that you can get a reminder when the next post appears by putting your email address in the Follow by Email box in the top right of this screen.)

Perito Moreno; a rare growing glacier

Perito Moreno Glacier is one of the chief attractions for visitors to Argentinian Patagonia, and quite justifiably so. It lies in the eastern fall of the Andes, some 60km west (in a straight line) of the touristy town of El Calafate, on the shores of Lago Argentino. This is a vast lake, extending all the way from El Calafate (and well beyond) to the glacier; it was 'discovered' (ie by Europeans) by Francisco 'Perito' Moreno, a nineteenth century Argentinian archaeologist, anthropologist and explorer of Patagonia. 'Perito' means an expert, and has a similar connotation to 'professor' as we might apply it respectfully to a learned person.  

The north face of Perito Moreno Glacier from approximately six kilometres away, across Lago Argentino.

The glacier lies within the huge Los Glaciares National Park, which covers some 700,000 hectares of Andean wilderness, including much of the Southern Patagonian Ice Field, the world's largest after Antarctica and Greenland. (An ice field is defined as a complex of glaciers which buries much of a mountain range.) To give a sense of scale to the photo above, the ice wall we can see towers more than 70 metres above the water surface (with another 100 metres of ice below it). The glacier arises 30 kilometres deeper into the mountains, and the final wall of ice (not all of which is visible in this shot) is five kilometres wide. 

Location of Perito Moreno, near to the Chilean border (which is within the Andes).

The map, taken from Google Earth, shows part of the ice field, the foot of the glacier (at the end of the red arrow),
Lago Argentino, El Calafate, and the approximate point from which the first photo was taken (at the yellow diamond).

This map shows too how the southern arm of the lake is cut off by the glacier pressing against the opposite shore of the lake; the water rises in the southern arm, fed by local runoff, until it is many metres above the level of the rest of the lake. Eventually (on average every five years or so) it breaks through dramatically; this aerial photo was taken on 21 March 2016, which was only three weeks after the most recent rupture. I am surmising that the pale colour of the arm is because it is normally shallower than the main body of water, but I'm open to more informed suggestions.

A closer shot of the glacier wall from the same location as the photo above.
The southern arm of the lake is in the foreground with the main lake out of sight beyond the glacier.

The first time I visited Perito Moreno, more than 10 years ago, I joined one of the daily trips which cross the lake, and conducts walks on the glacier - closely supervised by very well-informed guides, certainly on that occasion.

The boat which conveyed us - the dents in the bow were food for thought!

The ice wall becomes more impressive as the boat approaches it.

The blue in the ice develops as snow falls on the ice and is compressed by later falls, until air bubbles are squeezed out and crystals grow; ice with small crystals and air bubbles appears white. This blue was one of the things that delighted me that day - it was the first glacier I'd ever seen! Here are some images from then.

The glacier's edge, as we approached it.

Ice cave.

The view back to the lake, from atop the glacier.

Glaciers carve out landscapes, and move vast quantities of earth and rock across the surface, and the walk enabled us to see the impacts of that.

Gouges in the rock left exposed when the glacier retreats in summer; the bottom of the glacier
acts like a huge coarse sheet of sandpaper.

 

Moraine is material moved, perhaps for tens of kilometres, under the glacier and left behind when
the ice seasonally retreats. This is terminal moraine, ie at the end of the glacier.

As suggested in the post heading, Perito Moreno is most unusual in this worryingly warming world, in that it appears to be defying trends and logic, and expanding. Since the glaciologists can't agree how to explain it, I'm afraid I won't be trying to!

That was a fascinating experience, and I enjoyed it, but overall I think I prefer the walk that follows the lake shore, on a raised board walk, looking across to the glacier wall.

The glacier face; in the left foreground is the point where the southern arm of the lake (to the left) breaks through.

What is very obvious is the raft of broken ice in the water at the base of the glacier - and of course that is where it originates. 

From closer, the scale yet again becomes evident; many of the pieces of floating ice are huge.

The glacier is a slow river of ice, and at the foot ice is constantly breaking off as it it pushed by the millions of tonnes of ice behind it.

You've got to be lucky and patient to observe the moment of calving, and I was a touch too slow
to get the best of this one.

The results however are very easy to observe as they start their long journey across the lake to eventual oblivion; and some of those results are very odd indeed!

Some very singular icebergs, in which it is not hard to find animal-like shapes!

The surrounding forests are beautiful old-growth Nothofagus, or southern beech, forests, with a startling similarity to such forests in Tasmania and New Zealand - as well they might, having their origins in Gondwana when such forests stretched from a united Australia and New Zealand through Antarctica to South America - and of course were carried across the world when the continents ripped asunder. 

Old growth Nothofagus forests, above and below, straight out of ancient Gondwana...

Apart from the beeches themselves - and Nothofagus species are found in those Australian and New Zealand cool temperate rainforests - other plants are familiar too. 

Winters Bark Drimys winteri, Family Winteraceae.
This is regarded as one of the most ancient of living flowering plant families, offering an insight into
how early flowering plants may have looked. Very similar plants in Australia were until recent decades
also called Drimys, but are now known as Tasmannia.

Gavilea araucana, a member of an orchid genus of some 15 species, mostly found in the cold
far south of South America.

Close-up of the lovely flower.

Animals are present, but the busy and not always respectful hordes of tourists keep them at bay. There are always some treats however.

Patagonian Grey Fox Lycalopex griseus near the foot of the glacier.

A day in wild Patagonia would not be complete without a condor, and Perito Moreno rarely disappoints.

Andean Condor Vultur gryphus soaring against the mountains;
the snow drifts create a somewhat surreal effect.

But the highlight of my most recent visit was a much smaller predatory bird, who would probably have preferred to be overlooked...

Austral Pygmy Owl Glaucidium nana.This little owl, no more than 20cm high, hunts in a range of habitats
in the south of the continent, taking prey (mostly birds) up to twice its own size.
It is often active during the day; this one was by a busy track.

Most of my time in Patagonia has been in Chile, but my two visits to Perito Moreno stand out as highlights of my time in the wild south. Consider finding out for yourself.

BACK ON THURSDAY
 (And remember that you can get a reminder when the next post appears by putting your email address in the Follow by Email box in the top right of this screen.)