Fabulous Feathers

I've talked on many occasions before about feather colours - look on the right of this page under Labels, then Colours in Nature for some links - but I haven't actually looked at the feathers themselves, and they are truly wonderful. They are a key, perhaps the key, to the extraordinary success of birds, and they help determine how and where it lives. A measure of their importance is that, despite their proverbial lightness, they weigh two to three times what the bird's skeleton does.

Cinereous Harrier Circus cinereus, Los Glaciares NP, Argentina.

Feathers, or at least filamentous scales, evolved well before the development of flight and in at least two other dinosaur groups - the certatopsid group, the poster species of which was triceratops, and the flying pterosaurs - as well as the running carnivorous theropods, a branch of which became birds. The purpose of these was doubtless insulation, in animals which were controlling their internal temperatures, or becoming 'warm-blooded' as we might carelessly put it. (Consider that a 'cold-blooded' lizard on a rock at 40 degrees has warmer blood than the mammal passing by.)

More complex branched feathers arose, as far as we know, only among the theropods, but were possessed by many non-flying species of them. It seems that display was an important function before various small dinosaurs adapted long arm and leg feathers to assist in gliding, which ultimately evolved into true flight.

A feather is a marvellously complex structure. A 'basic' feather - and we'll get to the different types of feather in a while - comprises a shaft with barbs projecting along it on each side. The base of the shaft is hollow, where it is embedded in the skin; this is the calamus. The rest of the shaft – the rachis, or quill – is solid. Along each side of the barb, in turn, are rows of barbules. The barbules on one side of the barb are hooked, those along the other side are looped, so that each barbule ‘zips’ onto the next one, like velcrose.

Basic parts of feather (of Australian Bustard - found dead by the road!).

Enlargement of part of the same feather - still far too small to see the barbules, though we can
see on the right where some barbs have become 'unzipped'.
Take a feather, pull the barbs apart (feel the resistance to your pull),
then rezip them by running your fingers along the barbs.
I love how the intricate patterns (formed by melanin pigments) run across all the barbs!

As well as keeping warm air in, a bird (other than some diving birds like cormorants and darters) needs to keep water out – waterlogged feathers are heavy and cause chilling by expelling the insulating air layer. Preening oil can be part of this waterproofing, but so is the structure of the surface feathers. Barbs on the outer surface are more widely spaced, which has the effect of causing the water to form drops, which are readily shed.

Wing and tail feathers are very enlarged and strengthened, shaped to give lift and steering. 

Flight feather (of Australian Pelican) - very stiff and strong.

The wing feathers, the flight feathers, are called the remiges, singular remix, and are divided into the primaries and secondaries. The primaries are longer, and are attached to the outer bones of the wing, the modified hand and wrist bones. The secondaries are shorter, and grow from the larger inner bone, the ulna. The tail feathers, or retrices, play a role in steering, balancing and braking. Here's the Cinereous Harrier again to demonstrate.

Wing and tail coverts overlie the flight and tail feathers above and below (at the front of the wing and the base of the tail) to protect them from damage and to provide a smooth surface to promote aerodynamic efficiency.

Contour feathers, the other visible body feathers, cover the surface of the body and also aid flight by streamlining. Most contour feathers also have a downy base, for insulation. 

The extensive downy base is evident; down feather barbs have no barbules, so are loose and woolly.

Many adult birds also have a layer of down feathers (with no barbules at all) under the contour feathers; these grow from different follicles from those from which contour feathers sprout. Many chicks however are covered in a layer of 'natal down'. These insulating feathers grow from the same follicles which will later produce their adult feathers.

Natal down on Swallow-tailed Gull Creagrus furcatus chick, Galápagos (above),
and on Darwin's Rhea Rhea pennata chicks, Torres del Paine NP, Chile (below).

 

These chicks are still substantially covered in natal down, but are also developing flight feathers.
Red-tailed Tropicbird Phaethon rubricauda, Lady Elliott Island, Queensland, above;
Australian Darters Anhinga novaehollandiae, Canberra, below.

 

As suggested earlier it is not of course the feathers per se which insulate, but the layer of air they trap - the same principle as double glazing. We've all seen a small bird in winter looking twice as big as normal, with its 'doona fluffed up'. The feathers are controlled by tiny muscles which can raise them, or indeed squeeze them flat in hot conditions. No sleeping bag manufacturer has ever produced a synthetic substitute for feather down which is anything like as efficient.

Contour feathers often have a woolly ‘aftershaft’, at the base, though it is mostly very small and not easy to see among the downy base. It is believed to be primitive remnant trait, based on who does and doesn't have them - passerines, the most modern Order of birds, don't. However in emus and cassowaries, among the most ancient of living birds, it is the same length as the rest of the feather.

Emu feather with aftershaft.
The barbs have no barbules, hence the characteristic 'haystack' appearance of emus, and the
hairy look of cassowaries.

Then there is a range of specialised feathers which are not present in all birds.

Single shafts of bristles around the eyes or base of bill are believed to be sensory, but probably also play an important role in protecting the eyes from struggling prey; they are primarily observed in birds which catch insects. 

Tawny Frogmouth Podargus strigoides (on nest), Canberra

Paperbark Flycatcher Myiagra nana, Nitmiluk NP, Northern Territory.

Filoplumes are also single shafts with abundant nerve endings at the base. They are scattered among other feathers, especially flight feathers, and apparently convey information about the movement of other feathers, so they can be adjusted if necessary. We know them as the ‘hairs’ on a plucked chook (ie 'chicken' to my non-Australian readers). 

Powder down is a particularly remarkable feather type which occurs among ordinary down; the tips of the feathers disintegrate into a powder of keratin, used for preening and conditioning - like talc powder, though chemically quite different. This remarkable feather type has evolved independently among many bird groups; the down feathers may be scattered throughout the body, or concentrated in patches. Powder down feathers are not moulted with other feathers, and grow continually.

Mealy Parrots Amazona farinosa at Blanquillo Clay Lick, Peruvian Amazonia.
The floury (ie 'mealy') appearance is due to an abundance of powder down.

White-necked Heron Ardea pacifica, Grenfell, New South Wales.
All herons have powder down which they collect with the bill and pass to the foot to apply to the feathers.

Next time you pick up a feather, have a good look at it and admire it with the wonder due to a truly remarkable product of nearly two hundred million years of evolution.

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Bunya Mountains National Park; splendid isolation

Actually the Bunyas, in the hinterland of south-east Queensland, aren't really so isolated in terms of visiting them, but ecologically they represent a remnant of ancient Australia, rainforests left behind when the plains around them dried out, surviving in the cooler moister shelter of the ranges.

Subtropical rainforest creek line on one of the Bunya Mountains walking tracks.

The surrounding plains have been almost entirely cleared for agriculture but they were until relatively recently covered in dry Brigalow (Acacia harpophylla) forests and vine forest, or bottle tree scrub - as indeed the base of the Bunya Range still is. 

Bottle tree scrub, with Narow-leaved Bottletree Brachychiton rupestris.

The range is based on layers of basalt from volcanic eruptions, the most recent of which occurred 22 million years ago. While isolated it is functionally part of the Great Dividing Range, in that rain falling on the eastern slopes flows to the Pacific while water from the south-western slopes runs into the Condamine, and ultimately via the Balonne, Darling and Murray into the sea in South Australia.

Location of Bunya Mountains, 150km inland from the Sunshine Coast in south-east Queensland.

Famously the area was of enormous significance to indigenous people for the sporadic huge bounty supplied irregularly by the synchronised Bunya Pine seed production. It was a time when many peoples gathered and it was immensely important socially as well as economically; it's a story that's readily available and you can read accounts of it from people much more qualified than I am to tell it. Needless to say, tragically, those traditions were disrupted and then destroyed, not least due to the logging of the valuable timber resources of the range's forests. The last major gathering took place late in the 19th century; it seems to me that this underlines its importance, as much of the culture would already have been lost by then.

Europeans have been visiting the mountains for recreation since the 1860s, and in the 1880s a 12,000 hectare timber reserve was declared in an attempt to at least moderate the harvesting. In 1908 a 9,000 hectare national park was declared - this was the first major national park in Queensland (coming just months after the tiny Witch's Falls, now a section of the Tamborine National Park). Nonetheless logging continued for another decade or so! The park has since doubled in size to nearly 20,000 hectares and while logging has ceased, there are still conflicts from the proximity of residences and businesses high in the range on the park boundary - as these signs indicate.

These signs face each other across a narrow road - obviously enough,
the sign above is in the national park.

 

The subtropical rainforest, dominated in part by the mighty Bunya Pines Araucaria bidwillii, dominates the upper parts of the range (which rises to 1100 metres above sea level). The pines belong to one of the old Gondwanan conifer families, Araucariaceae; the species was named for John Bidwill, acting NSW Government Botanist and Director of the Botanic Gardens and later Commissioner of Crown Lands and chair of the Bench of Magistrates for the Wide Bay region of Queensland (then still part of New South Wales). He passed the material on to Sir William Hooker of Kew, who described the tree. 

Ancient emergent Bunya Pines; the dome-shaped canopy is diagnostic.
They are restricted to a few areas of south-east Queensland, plus a couple of small
relic populations far to the north in the tropics.

Bunya trunk; it has been claimed that the notches were cut by indigenous cone harvesters,
but it seems that this must remain just a good story. Inter alia, I'm sure those scars would have grown over
well before now; perhaps they represent former limbs.

The massive cone of the Bunya Pine (and a much younger bloke in a world where blogging
hadn't been dreamt of!). It is not wise to linger under the pines when cones are ripe!

Alongside the Bunyas grow the closely related Hoop Pines (though in theory they favour lower drier elevations). This species, A. cunninghamii (for the illustrious explorer-botanist Allan Cunningham), is much more widely distributed, found from northern New South Wales to New Guinea; it is also grown in timber plantations.

The very distinctive erectly ragged crown of Hoop Pines.

Clearly these Hoop Pines are growing in rainforest, complete with massive Bird's Nest Fern epiphytes.

Hoop Pine trunk, with the 'hoops' for which it was named.
Another significant difference from Bunya Pines is in the cones, which are tiny.

Like other subtropical forests this is a simpler forest than the tropical forests further north, but shares characteristics such as lianas, buttresses, epiphytes, strangler figs and many ferns, and is a lovely place to walk through; there is an excellent array of walks to choose from.

Bunya Pine-dominated forest.

An opening in the forest, with tree ferns and rapidly growing Giant Stinging Trees,
which specialise in colonising such clearings.

A tangle of fallen lianas.

An old, knotted liana.

A bank of ferns and cordylines.

Broad-leaved Palm Lily Cordyline petiolaris, above and below.
In the new lily taxonomy it is placed in the family Asparagaceae; it is found
throughout the near-coastal sub-tropics of Australia.

 

Leaf of Giant Stinging Tree Dendrocnide excelsa - it is literally a tree-sized stinging nettle, in the
family Urticaceae. You can see the stinging hairs around the chewed sections. The leaves always seem
to be nibbled, so the defences obviously only work against larger animals - but they certainly do work on me!

Buttresses on Churnwood Citronella moorei, family Cardiopteridaceae.
The Citronella was applied to a Chilean species; moorei for Charles Moore, NSW government botanist.

Strangler Fig Ficus watkinsiana; for more on stranglers, see here, but essentially they kill their host not
by strangulation but by shading them to death.
This one has a curious distribution in two isolated populations, one in northern New South Wales and south-east
Queensland, and one in tropical Queensland..

Cyathea cooperi, a tree fern, found along the eastern coast.
Unfortunately it has become an invasive weed in Hawaii and has invaded areas of southern Australia.

 Waterfalls feature on some of the walks.

Festoon Falls.

Paradise Falls; maybe a bit of hyperbole, but they are very pleasant!

Another favourite walk of mine in the Bunyas is the one up Mount Kiangarow, the highest point of the range (the walk actually starts high up and ascends very gradually). It starts in rainforest....

....but rapidly emerges into dry open forest, where a feature is the wealth of huge ancient grass trees, Xanthorrhoea glauca. They are certainly the largest of this species that I know, and only on Kangaroo Island have I seen others of similar size.

This magnificent specimen is at Burton's Well campground, at the start of the walk.

Avenue of grass trees along the track to the summit.

View from Mount Kiangarow, looking out over the park in the foreground and
the heavily cleared rich agricultural land of the Darling Downs beyond.

Another habitat which is of great interest in the Bunyas is the system of hilltop grasslands known as the balds. Their origin is unclear, though the presence of species restricted to them, including the locally endemic grass Bothriochloa bunyensis, strongly suggests they are natural. It is thought they are relics of the last glaciation; in recent times there has been considerable invasion of them by forest, which may be a product of global warming. Attempts are being made to counter this with use of fire.

Two views of some of the balds; there are well over a hundred of them along the ridges of the range.

Wildlife is rich, though I've not got a lot of photos - inter alia photography in rainforests is for those with better skills and equipment than I!

Carpet Python Morelia spilota, objecting at being asked not to lie on the road.
This is a scan of a slightly faded old slide from an early visit.

Red-necked Wallabies Macropus rufogriseus; along with some other animals they hang around
the visitor areas, but I prefer to show you slightly wilder ones where possible!

Brush Turkey Alectura lathami, another which has no problems making a living from visitors.
A mound-builder, which incubates its eggs in a huge pile of managed compost.

Male Superb Fairy-wren Malurus superbus. One of the most abundant and familiar birds in south-eastern Australia, but one more photo is never quite enough...

Female Paradise Riflebird Ptiloris paradiseus, one of three closely-related birds of paradise from
eastern Australian rainforests. An awful photo (again a scan of an old slide) but a special bird.

Juvenile (and wet!) Green Catbird Ailuroedus crassirostris; the two Australian catbirds are
relatively primitive bowerbirds which don't build display bowers, and which yowl loudly like cats
or crying babies, quite disconcertingly if you don't know them!

Topknot Pigeons Lopholaimus antarcticus, preening high in a Bunya Pine.
This big strange-looking fruit pigeon has no close relatives.

White-browed Scrubwren Sericornis frontalis. This active little group of birds had me fooled for a while -
I took them to be Yellow-throated Scrubwrens, but they are particularly yellow examples of the Queensland
race laevigaster. (If you're still wondering, the pale iris and distinctive white 'whiskers' are giveaways.)

 

And lastly this intriguing little character, twirling apparently contentedly at the end of a silken thread.

If you've not been to the Bunyas yet - or even if it's just been too long since you were there - take a detour when next you're in the vicinity, or even make a special trip! You won't be sorry.

PLEASE REMEMBER THAT I ALWAYS VALUE YOUR COMMENTS!
THEY CAN BE ANONYMOUS (THOUGH OF COURSE I'D PREFER TO BE
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