Not an Owl; some of the other night birds

It's a common, and perfectly understandable, assumption that all nocturnal hunting birds must be owls. Most of us don't usually get a good look at these birds unless we happen upon them when they're trying to sleep in the daytime, while hoping to escape the notice of the noisy day birds which always want to move them on. Moreover, even if we do get a decent look, they still look rather owl-like - big eyes, soft plumage, delicately patterned plumage, often mottled or streaked for camouflage. These 'not owls' are the potoos of South and Central America, the Oilbird of northern South America, the nightjars and nighthawks, found across most of the world, the frogmouths of Australia and south-east Asia and the owlet-nightjars of New Guinea, plus a few nearby islands (including Australia). Each of these groups forms a Family, and until recently all were placed in the same Order, but in 2021 it was broadly agreed that each of these Families was better understood as a full Order in their own right (see here and find Version 11.2).

Hopefully you've read this far! If so, please persevere - that's pretty much the end of the taxonomy lesson, and the rest is just about these very interesting groups of birds.

Tawny Frogmouth Podargus strigoides near Canberra; they typically spend
the day in the open, relying on their impressive camouflage for protection.

While we're on frogmouths we might as well continue with them. There are 16 species, and through most of their extensive range, which stretches from Australia to India, they are rainforest dwellers, many of them very hard to find. However the Tawny Frogmouth is the exception, being a bird of drier forests and woodlands throughout Australia, including the arid inland, wherever there are trees and open ground for hunting. They are found in suburbia, including in all Australian capital cities, and I'm sure that they are the most familiar night birds to most Australians.

Tawny Frogmouth and large chick, about to fledge (indeed it flew just a day after this),
in a park near our Canberra home.

Despite the apparent similarities with owls, there are significant differences. Whereas owls have forward-looking eyes (like us), frogmouths' eyes are more on the side of their head, like most other birds. They have broad shallow beaks for scooping up food (insects, plus some frogs and mice, taken mostly from the ground), whereas an owl's beak is sharp and narrow for tearing up prey. Owls hunt primarily with their feet, which are powerful and taloned like a hawk's; a frogmouth's feet are comparatively weak and are not used to seize food. Much the same comments could be made about the other 'not owls' we'll be meeting today.

 

While these photos don't show it to best advantage (mostly because these birds didn't choose a well-matching branch to roost or nest on), the frogmouth's camouflage is remarkable. The streaks in the plumage can resemble cracks in bark to a remarkable degree. The head is held upright to reinforce the impression of a broken branch. The eyes are closed, though, if the bird is approached too closely, they will open to slits, and the head will turn ever so slowly to keep the intruder in sight.    

 

As the previous photo suggests, nests are very flimsy and placed on a horizontal branch or a flat fork.

Adult on nest, Narrabunda Hill, Canberra.

Sometimes old nests of other species are repurposed by frogmouths.
 

Tawny Frogmouth on old White-winged Chough nest, Mulligans Flat NR, Canberra.
It may just have been perching, but it was in November when I'd expect them to be breeding.

The three Australian/New Guinea species are all in the genus Podargus; Marbled and Papuan Frogmouths are found in both islands, while Tawnies are only in Australia. I find this surprising though, given that they occur almost to the tip of Cape York, just across the narrow Torres Strait from New Guinea. Going further north-west, the 13 Asian species are only found on the other side of Wallace's Line; all are smaller and restricted to rainforest.

Papuan Frogmouth P. papuensis, Centennial Lakes, Cairns, above and below.
This tropical species is found north from about Townsville to the tip of York Peninsula,
and throughout New Guinea. It is usually found along rainforest edges and in
drier rainforest, which is generally known as monsoon, or vine forest. This pair was
roosting in mangroves, where they were surprisingly hard to see.

The third Australian species, the Marbled Frogmouth P. ocellatus, is notoriously hard to find in its rainforest habitat. It has two very separate small Australian populations, on Cape York Peninsula, and in the border ranges of near-coastal NSW and Queensland, as well as throughout New Guinea.

It seems logical to me to go from frogmouths to potoos, though the latter are in a different Order, as we have seen, and only found in the American Neotropics. Whenever I see them though I am struck by how much they resemble frogmouths, though that's entirely due to adaptations to similar lifestyles. Like frogmouths they hunt from a perch, but unlike them they take prey almost exclusively from the air, and never from the ground. Their camouflage is just as good but rather than perch on horizontal branches they use vertical stumps or broken branches, positioned upright so as to seem like an extension of the stump.

Great Potoo Nyctibius grandis, Pantanal, south-western Brazil. This is the largest
potoo, up to 60cm long, and is found from south-eastern Brazil to southern Mexico.

The seven species are found between them in every Central and South American country, though they are most prevalent in the Amazon Basin.

The Long-tailed Potoo Nyctibius aethereus, here at Tambopata Reserve in the southern Peruvian
Amazon, is found throughout the Amazon basin, and in the southern Brazilian Atlantic forests.
I love how the white wing patch resembles lichen on a tree trunk!

Common Potoo Nyctibius griseus, Muyuna Lodge, northeastern Peru. It is found
almost throughout South America except for the far south and the higher Andes,
and in much of Central America.

They don't build a nest, simply laying a single egg in a depression on a branch, or on top of a stump. The pale chicks have their own camouflage, resembling a lichen-covered branch.

Common Potoo chick, Yasuní NP, Ecuadorian Amazon.

Great Potoo chick, Muyuna Lodge, Peru.

Unsurprisingly, I am a big fan of potoos, not to mention the amazing guides who can reliably spot them!

The smallest of these 'not owl' Orders is represented by just one species, the somewhat enigmatic Oilbird Steatornis caripensis, found along the slopes of the Andes and in the lowland forests of northern South America. While distantly related to the other Orders, it differs from those birds in almost every way except for being nocturnal.

Oilbird above a rainforest waterway in Yasuní NP, Ecuadorian Amazonia.
My friend and guide extraordinaire Juan Cardenas were in a canoe doing
reconnaissance for a tour when we saw what we thought was a nightjar above
our heads. When we arrived back at our lodge, we both realised what we'd
really seen, for the first time for both of us.

 

For a start, of all these 'non owls' only the Oilbird is fully vegetarian, living on fruits of palms and laurels. Along with the New Zealand Kakapo, a flightless parrot, it is the world's only nocturnal fruit-eating bird. It finds the fruit by night by smell, and can travel up to 120km from their roost to feed. Moreover it not only has the remarkable night-sight that we'd expect, but it also uses echo-location, like a microbat. This is because, like the bats, it breeds and largely roosts in caves, and needs the 'super power' to navigate in the total darkness. This is not unique among birds, but it is very rare - the only others that I am aware of using it are some swiftlets, which also nest in caves. If caves are not available, Oilbirds will also roost in deep rock crevices and ravines, and it has recently been discovered that they regularly roost in trees in the rainforest too.

Oilbird roost in a deep slot canyon, at the Quiscarrumi Bridge near Moyobamba
in northern Peru. The birds look like brown rice grains on the ledge
in shadow in the left foreground.

A closeup, somewhat hazy, view of the roosting Quiscarrumi Bridge Oilbirds.

Of the five 'non owl' orders in the torch light today, the delightful little owlet-nightjars form something of an outlier - in fact their closest relatives (though still distant) are the swifts and hummingbirds! They are essentially a New Guinea group, where are seven species. One of these extends to and throughout Australia, and there is an endemic species in each of the Indonesian Moluccas and New Caledonia. (There was also a flightless New Zealand species which became extinct in about 1400 when rats arrived in New Zealand with humans.)

 

The elegant little Australian Owlet-nightjar Aegotheles cristatus (also found in the savannas of southern New Guinea) is less than 25cm long and is found in open country throughout the continent. Its musical churring call is a familiar night sound, including in suburbia near bushland. It is the only open country member of the group, the rest being rainforest birds. It hunts insects like a flycatcher does, taking off from a perch to seize prey in the air or from a branch or the ground.

Australian Owlet-nightjar catching the sun in a eucalypt hollow in the
Australian National Botanic Gardens in Canberra. This is typically how we
see them, though I've also seen them roosting on a branch. They rely heavily
on such tree hollows for both roosting and breeding.

Finally there is the biggest family of 'non owls', the nightjars (which includes the American nighthawks). There are 96 species found on every vegetated continent, quite a few being inter-continental migrants. They live in forest and deserts and big cities. All are superb aerialists, hunting insects by sight in apparent complete darkness, though many can also be seen hunting in the dusk, when their elegantly long wings and aerial virtuosity are there to be admired. I have enjoyed many an evening in camp watching a nightjar hunting, swooping past in the gathering twilight, working up and down the open area of the campground, or flashing repeatedly over a pool or river, intercepting the insects rising from it. And listening! Nightjars have the most amazing calls, wild rising, accelerating bursts of gobbling and bubbling. The Large-tailed Nightjar of northern Australia sounds like someone repeatedly hitting a hollow log with an axe.

Blackish Nightjars Nyctipolus nigrescens, eastern foothills of the Andes in
northern Ecuador. Roosting on or near the ground is typical of nightjars,
and this one specialises in rocks or fallen tree trunks.

And now for the very embarrassing and embarrassed confession. I have quite a few photos of nightjars, some of them reasonably acceptable (though you may judge that below), but, but... I have never managed to take one of any of the three Australian species, though I've seen them all. The one I've seen most often is the Spotted Nightjar which occurs across most of the inland of the mainland Australia, in dry open habitats. By day you typically you first see them when they flush from the ground. They spend the day roosting, often in the shade, among ground litter or rocks, where they effectively disappear, courtesy of their superbly camouflaged plumage. I have watched carefully to see where they've landed (they often don't go far) and cautiously approached to get a photo - and have failed to find them every single time! I know. As I said, embarrassing. Let's move along to some that I have managed to see (with help on each occasion I should add), in Africa and the Neotropics of America.

Common Pauraque Nyctidromus albicollis (the origin of the common name seems to be
something of a mystery) is the commonest American nightjar pretty much throughout its range,
which includes most of Central and South America. The far-flung sites of
these two photos gives some indication of this. The one above was roosting near
our room at Muyuna Lodge on the edge of Amazonia in northern Peru...

... while this one was by the track in the northern Panatanal, south-western Brazil.
They are often encountered on tracks or roads at night.

Also in the northern Pantanal is this one, which I am very cautiously suggesting
is a Rufous Nightjar Antrostomus rufus, but without much confidence.
At the time it was called as a Little Nightjar Setopagis parvula, but
that doesn't convince me either. Any suggestions welcomed.
(Frankly it doesn't much resemble anything in the Pantanal field guide!)

I mentioned earlier that nightjars often hunt insects over water, so it's no surprise to see them along rivers, though the sheer numbers of these Sand-coloured Nighthawks Chordeiles rupestris along the Manu River in the southern Peruvian Amazon basin astonished me. (Nighthawk is a name used in the US for nightjars that are members of the genus Chordeile).

This was just a small part of a loose roosting flock.

A closeup of a couple of members of the same flock, roosting on flood debris.
It is found along river corridors in the western Amazon basin.

More surprising was seeing this Lesser Nighthawk Chordeiles acutipennis on the beach in Costa Rica, though apparently this is one of its normal habitats while overwintering there. It breeds in deserts in the south-western US and Mexico, and then flies south to Central and South America for the rest of the year, where it prefers watery habitats.

Lesser Nighthawk roosting on driftwood at the mouth of the Tarcoles River,
eastern Costa Rica.

Some nightjar males have spectacularly long and elaborate tail feathers or flight feathers for display purposes; here are some, though the first couple are unfortunately for us not adult males.

Fledgling Ladder-tailed Nightjar Hydropsalis climacocerca, Yasuní NP, Ecuador.
It is found throughout the Amazon Basin. When older, especially if it's a male,
it will have a curious tail structure, with the longest feathers being the central and
outermost ones. I confess that this doesn't say 'ladder' to me, but that comes from the
translation of the Latin name (not that that helps us of course). More importantly,
males fan the tails while flying slowly low over water to attract a female's attention.
It evidently worked for this one's parents!

Scissor-tailed Nightjar Hydropsalis torquata, Peruibe, on the coast north of
Sao Paulo, Brazil. Adult males have a pair of long slender outer tail feathers
which often break, so this could be such an unfortunate male, or a female.
Oddly the tail doesn't seem to feature in courtship displays, which
take place on the ground in an open space, while he claps his wings overhead!
This one was roosting in coastal heath just above the ground.

  

Pennant-winged Nightjar Caprimulgus vexillarius, Murchison Falls NP, Uganda.
This bird seemed to be injured, perhaps by another car. The extraordinary
pennants are hugely extended second primary feathers (ie growing from
about the centre of the wing) which grow longer each year, being shed
with the annual moult after breeding. They are used in courtship displays both
in flight and while perched on a rock or termite mound, with his back to the female.

Standard-winged Nightjar Caprimulgus longipennis, Ngaoundaba Ranch,
central Cameroon. His camouflage is exquisite. He is facing right, with his
head just under the two green leaves at the centre right of the photo. His
ornamentation also features a greatly extended flight feather on each
wing, though in this case much of the length comprises a bare shaft,
with the two black 'standards' at the tip, and clearly visible here.
The standards trail behind him in normal flight but are held straight up
when displaying, which occurs in leks, with many males gathered to compete.
It must be a spectacular event!

Lyre-tailed Nightjar Uropsalis lyra, Mindo Valley, north-western Ecuador.
This unlikely beauty is found along most of the Andes from Ecuador to northern
Argentina. Its behaviour doesn't seem to be well known, though males apparently
also form leks, competing with females through their flight display. To this end the
males' tails are up to 60cm long.

And I think that's probably enough, but hopefully you've been able to find something of interest here. One day I'll do a post on birds that are owls, but the not-owls are, I think, also fascinating and diverse. Thanks for bearing with me, and them.

Tawny Frogmouths by the Murrumbidgee River south of Canberra.

NEXT POSTING THURSDAY 19 OCTOBER
for more on Costa Rica - some animals

 

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A Celebration of Weird Bills

And by 'weird bills' I don't mean the sort where someone wants you to pay lots of money to renew a subscription that you never had!

A decade ago I wrote a brief irregular series of short posts on unusually adapted bird bills; those are pretty much lost in the mists of time but I've decided to resurrect the idea and build on it for today's post. A bird's bill (or beak if you'd prefer, there's no difference) is a wonderful structure, and is the sole food-gathering tool for most birds, as well as being fundamental to preening, nest-building, chick-feeding any many courtship activities. It is not too dissimilar to the jaws of other vertebrates in comprising upper and lower jawbones (mandibles) but it is covered in a thin horny or leathery keratin sheath. The top mandible is connected by three bony prongs to the forehead and sides of the skull, so unlike in a mammal's jaw the top mandible is moveable as well as the bottom one, enabling a significant gape. 

Let's start with a couple of the biggest bills, and one of my favourite birds (though that tends to depend somewhat on which bird I'm watching at the time). 

The claim to fame of the fabulous Sword-billed Hummingbird (Ensifera ensifera) is that
it has the longest bill of any bird relative to its body size. Indeed it is also claimed to
be the only bird with a bill longer than its body. Yet another claim is that it always rests
with its bill held upwards, because it's too heavy to hold horizontally, but this female
didn't seem to realise that.

I first saw the species (this photo commemorates that occasion) in Ecuador, at the delightful Yanacocha Reserve, 6,700 hectares of cloud forest on the northern slopes of Pichincha Volcano, across the ridge from Quito. Like other precious Ecuadorian cloud forest reserves, it is run by the admirable Jocotoco Foundation. While the Sword-bill feeds on a variety of tubular flowers which don't require the remarkable length of  bill, it seems to have co-evolved with passionfruit flowers, and especially the species Passiflora mixta. Both the bird and the flower live in a long strip of high elevation cloud forest (between 2500 and 3400 metres above sea level) along the Andes.

A related species of Passiflora at San Isidro Lodge in north-eastern Ecuador. The flower tube
of P. mixta is even longer than this, and probably no other bird can reach the rich nectar
supply at the base of it.

Well that's relatively the longest of any bird bill, but what about in absolute terms? That honour seems to belong right here in Australia, with a very familiar bird - the Australian Pelican Pelecanus conspicillatus. 

A male's bill can be up to 50cm long. The famous pouch, of thin stretchable skin,
is supported by a pair of surprisingly delicate long bones, but can hold up
to 13 litres of water.

The important point is that pelicans do not carry food (or water) in the bill, but eat it immediately.
As soon as a food item, nearly always a fish, is scooped up along with the surrounding water,
the pelican presses its bill back against the breast to squeeze the water out.
As can be seen here, pelicans (along with gulls and owls) can spread the bones of the bottom
mandible to increase the width of scoop. The fish is then manipulated to be swallowed head first.

As we'd expect, in most birds (though not the ones we're looking at today) the upper and lower bill mandibles are essentially the same size and shape so that they fit together snugly when closed. However if 'biting' or tearing is required, the upper mandible is often hooked to provide grip and leverage to rip and crush flesh, hard seedcases or even wood. In this case the tip of the lower mandible is often broad and square; when closed the top hook fits over it. Here are a couple of examples.

Yellow-tailed Black-cockatoo Zanda funerea breaking open Banksia marginata cones
to extract the seeds (in our backyard in suburban Canberra.) In this situation the
force is exerted by the bottom mandible against the top, which hooks into the cone.

The same cocky species has ripped deep into this very hard-wooded Blackbutt
Eucalyptus pilularis to extract moth or beetle larvae.
Near Ulladulla, south coast New South Wales.

Wedge-tailed Eagle Aquila audax with road-killed Red Kangaroo carcase, far
north-western NSW. The hooked bill will have no trouble opening the body.

However in a few specialised cases, this hooked upper mandible is greatly attenuated for extracting edible material from within a hard case with a small access. The big apple snails (Pomacea spp.) are abundant in Neotropical wetlands, but despite (or because of) being a valuable potential food source are protected by their large, smooth, hard shells with a small opening. However two species of raptors have evolved a long slender upper mandible to solve the problem; they are snail specialists.

Snail Kite Rostrhamus sociabilis, Panatanal, south-western Brazil,
at work extracting an apple snail, above and below. (The Slender-billed Kite Helicolestes hamatus
has developed a similar bill for the same purpose.)

But snails aren't the only food hiding in a hard shell; many seeds do the same. In the south-west of Western Australia the Marri tree Eucalyptus (or Corymbia) calophylla dominates large areas of dry forest; its fruit are not entirely dissimilar from an apple snail in appearance.

Marri fruit near Perth; the cases are phenomenally hard, but a couple of bird species endemic
to the area have solved the access problem in the same way the South American kites have. Both
these birds are experts at extracting the seeds without damaging the fruits.

Red-capped Parrot Purpureicephalus spurius, Albany,
a truly glorious large parrot, and the sole member of its genus.

The key feature of the Red-capped Parrot from our perspective however is the extended upper bill, fairly clear in this picture. Experienced older birds show great dexterity in nipping off the hard ripe Marri fruit, holding it in one claw, testing it and, if it is of good enough quality, rotating it while inserting the upper bill to extract the seeds. (Green fruit are simply chewed apart.) An earlier study found that 54% of Red-capped Parrots in winter had been eating Marri seed. 

Given the value of the resource offered by Marri, it is not so surprising that another bird has independently come up with a similar solution to the issue of accessing the seed. This is Baudin's Cockatoo Calyptorhynchus baudinii, named for French commander Nicolas Baudin, sponsored by Napoleon to lead of one the most impressive exporatory expeditions ever to visit Australia, in the first years of the 19th century. (I won't digress here into the vexed question of whether we should be lumping animals with people's names, but it was certainly simpler when the two white-tailed black-cockatoos were referred to unequivocally as Short-billed and Long-billed!) As you'd expect from the previous story, Baudin's is the long-billed version.

Baudin's Cockatoos, Stirling Ranges NP. The special mandible is not as clear as it is in the
Red-capped, largely because the bill is part-hidden in feathers, though the light isn't helping.
In this pair it can best be seen in the female (with pale bill) on the left.

Baudin's Cockies are even more dependent on Marri than the Red-Capped Parrot, with wood-boring grubs comprising most of the rest of the diet. Sadly they are listed as Endangered, by the IUCN and both Western Australian and Australian governments. The single population is estimated to comprise between 10,000 and 15,000 birds; the main threat formerly was habitat clearance, while now it is regarded as a mix of loss of mature Marri trees (the key food source), competition for nesting hollows with feral Honeybee colonies, and illegal shooting (primarily by orchadists).

Another Australian cockatoo has also evolved such a bill, but for an entirely different purpose. 

Meet the Long-billed Corella, Cacatua tenuirostris, here at Urana in
south-central NSW. Its long upper mandible evolved to extract tubers, of a
native daisy species, from the ground.

Murnong, or Yam Daisy, Microseris lanceolata, here in Canberra.

The daisy is not uncommon, though never abundant, but once it was almost unimaginably profuse. Accounts from the grassy plains and open woodlands of southern New South Wales and northern Victoria tell of swathes of Murnong flowers turning the plains golden to the horizon. Their small sweet tubers were harvested by Aboriginal people, eaten raw or roasted to a delicious treacly consistency. European settlers learnt the trick from them.There are stories of wagon wheels turning up thousands of Murnong tubers from the soft soil, leaving them to rot on the surface. Then the sheep came, eating the plants and learning to push into the soil to eat the tubers as well. The plough finished the job. 

 

The corellas used to come in vast flocks to feed on them, but when the Murnongs largely disappeared so did the corellas. They rebounded when they found that the grains which replaced the Murnong were also edible, but of course this was a capital offence and the numbers fell again. Today numbers seem to have again recovered within their fairly small range of south-western NSW and western Victoria, partly due I suspect to their ability to adapt to eating the tubers of exotic weeds.

But what about the lower mandible; can that be adapted to a particular food-gathering purpose? Well of course it can - nature can do anything!

The skimmers comprise three species (one each in Africa, southern Asia and the Americas) of birds in the gull family (though until recently they were given their own family). They are distinctive birds with large bills, usually seen loafing on sand bars or mud banks either in rivers or at the coast.

Black Skimmer Rynchops niger, Pantanal, south-western Brazil.
Here you can clearly see the much longer and heavier lower mandible.

African Skimmers R. flavirostris, Queen Elizabeth National Park, Uganda.
You can click on both these photos to better see what I mean.

But for what purpose? This photo, ordinary as it is, gives you the answer.

Black Skimmer 'skimming', Isla de Chiloé, southern Chile. It is flying along steadily, just above the water, with that long lower mandible cutting the surface. When it contacts a small fish or shrimp it automatically snaps shut, flipping the snack inward. Wonderful!

OK, so much for unusually long slender bills; what about bills that seem abnormally flat and wide for scooping? No problems. Here are two examples in totally unrelated water birds. The first is the Shoebill Balaeniceps rex (ie 'king whale-head!'), sometimes referred to as a stork, but actually the only member of its entire family. Its massive bill is well over 20 centimetres long - only pelicans and some large storks have longer bills.

Shoebill, Murchison Falls National Park, Uganda.
The slightly mad-looking eyes can be a bit disconcerting, but more so I suspect
if you were about to be seized by that huge bill! They mainly prey on fish, especially
lungfish, concentrating on low-oxygen water where the fish are forced to come
regularly to the surface to breathe.

From this angle the savagely hooked tip is obvious, as well as the mass of the bill.

Across the Atlantic in the mangroves and streamside forests of the Neotropics, from Mexico to northern Argentina, lives a bird with a surprisingly similar bill to the Shoebill, but though it is equally massive relative to the bird's size, the Boat-billed Heron is only a third as big as the Shoebill.

Boat-billed Heron Cochlearius cochlearius, Pantanal, Brazil.
The very big eyes tell us that it mostly nocturnal, so we can only see it
in the very late afternoon and at night. It is probably not particularly uncommon
but because it can mostly only be seen from a night-time boat ride, it seems scarce.

The strange bill led it to be regarded as 'not-a-heron' (and there are some who would reinstate the older view that it belongs to a separate family) but the general opinion is that it is an out-lying member of the heron family. It snaps up a range of prey, especially fish and invertebrates and small land mammals, often using its bill as a scoop in a way that no other heron does that I can think of. 

While typing this I've thought of another, entirely different, group of birds with similar broad scooping bills. The frogmouths comprise a family of well-camouflaged nocturnal birds from Australia-New Guinea and south-east Asia, mostly dwellers in dense forests. The best-known however is the Tawny Frogmouth Podargus strigoides, found in open forests and woodlands throughout Australia. Their short broad bills enable them to 'swoop and scoop' on prey, from large insects and spiders to frogs, lizards and even small mammals and birds. They are related to nightjars, swifts and hummingbirds!

Papuan Frogmouth Podargus papuensis, Cairns, north Queensland.

Finally a couple of bills that really don't fit any sort of pattern used by any other birds. 

 

Toucans, from the Neotropics, have famously huge colourful bills with which they toss down fruit, and extract nestlings from tree hollows. However we now know that the driving force behind the bill is its role as a heat disperser, to manage body temperatures in the tropics.

Toco Toucan , Pantanal, Brazil.
Rather than reiterate things I've written about in detail recently, see here for more on
toucans in general and here for the temperature-management story.

Flamingoes have an extraordinary feeding behaviour, which requires an extraordinary bill. In all the birds we've looked at today, the top mandible is the larger one with the flexible lower one working against it. In flamingoes the opposite is true.

American Flamingo Phoenicopterus ruber, Galápagos Islands.
Here the lower mandible is clearer larger than the top one.

What makes this seem especially peculiar is that the flamingo then turns its head upside down in the water so that the bill is almost horizontal, to feed with its bill in the conventional bird shape - larger mandible upwards! Presumably only thus can it get its bill close to and parallel to the substrate.

American Flamingo, same location, feeding in shallow water. It is separating water and
unwanted muddy particles from food items using a large, fatty, highly sensitive tongue with
numerous fleshy protuberances (lamellae), complemented by a keeled bill also fringed with
fleshy lamellae. The tongue is used as a pump which beats from five to 20 times a minute to
suck in beakfuls of muddy water and wrigglies - including algae, small fish and invertebrates -
and to expel unwanted gunk via a complex set of movements. Remarkable.

And while all these bills are, I believe, fascinating variations, I've left one of the most peculiar and  mysterious - ie whose function has only recently been properly understood - until last. There are two species of openbill stork, genus Anastomus, one in Africa and one in Asia. They, like the Snail Kite earlier, feed on the big apple snails but their approach is quite different. There has been a lot of debate as to how they use this structure to extract the snails, not least because the process is both rapid and mostly occurs under water. It is now agreed however that despite earlier beliefs they do not break the shell, or use the gap to carry snails away.

African Openbill Anastomus lamelligerus, Entebbe Botanic Gardens, Uganda.
You can see readily enough the outward curve towards the end of the lower mandible, but not
obvious from this angle is the twist to the side, so that the tips don't meet. Stalked pads at the
tip of the upper mandible hold a big Pila snail against the ground (or underwater mud) while
the lower tip stabs past the protecting operculum to cut the muscle which holds the flesh
in the shell. Even more remarkably a narcotic in its saliva trickles down the bill to assist the
process by relaxing the snail.

Well, there's probably nowhere to go after that story, at least in my opinion. I've gone on longer than I intended, but that's the (only) problem with good stories. Maybe we can even follow this thread in different directions one day. Meantime, thanks for perservering!

NEXT POSTING THURSDAY 13 OCTOBER

 

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