Feather Care; it's life or death

A feather is a truly wonderful thing. Birds, the most numerous group of land vertebrates, owe their spectacular success to their feathers, which evolved from the scales of their dinosaur ancestors. The original function of these finely-divided scales was to provide insulation by trapping a layer of air around the owner's body (like the principle of double-glazed windows). In time they developed further to enable flight (one of only four times this has happened in the history of life on earth), and to form the basis of sometimes spectacular courtship displays. (And I have that in mind for a future blog post too.) Small wonder then that a considerable part of every bird's day is devoted to high-grade care and maintenance of its feathers. 

I don't want to spend a lot of time on the feathers themselves, though it wouldn't be hard to do so, but I do need to show you the basic structure, so you can get a better idea of what the birds in the following photos are actually doing.

This shows the basics of a feather (which I found on an outback roadside, in this case
the former property of an Australian Bustard). The most important single point
is that a feather isn't a solid vane, but comprises hundreds of fine barbs growing
from the central quill (or rachis).

If you click on this close-up to expand it, you can see the individual barbs.
What you can't see without a microscope is that the barbs are 'zipped' together by
rows of barbules along each side of the barb, lined with hooks along each edge,
which mesh like velcrose. If you gently pull on the feather to make an opening
like the one on the right, you can feel the resistance as the zips are opened.
If you run your fingers along the opening you will rezip the barbules.

And every bird must spend a considerable amount of time every single day in feather maintenance, including 'rezipping' every feather. Here are just a few of many photos I could have chosen, in a wide range of different birds, showing the attention to detail associated with the daily preen. The first three clearly show a single feather being rezipped.

Black Swan Cygnus atratus, Pambula, south coast New South Wales.
This bird is moulting its flight feathers, so is temporarily unable to fly.

Eurasian Coot Fulica atra, Canberra, attending to its wing feathers.

Yellow-billed Spoonbill Platalea flavipes, Jerrabomberra Wetlands, Canberra,
also paying careful attention to its crucial flight feathers.

 

Mistletoebird Dicaeum hirundinaceum, Milang, South Australia,
conscientiously working on his secondary flight feathers.

However there are very many more smaller feathers which play other roles, equally important, especially the contour feathers which cover the entire body and provide streamlining. These include the coverts which cover the base of wing and tail feathers, and the ear openings. Beneath the body contour feathers are fluffy down feathers for insulation. All of these also require care, but much of this preening occurs beneath the layer of feathers so it's not easy to see the detailed action. It's obvious what the bird's doing though! Much of this activity occurs during the day when the bird's finished its morning feeding, and while so occupied it can become quite absorbed in its work and relatively unaware of us watching it.

Blue-faced Honeyeater Entomyzon cyanotis, in a street tree in Griffith, NSW.

Brown Pelican Pelecanus occidentalis, Puerto Ayora, Galápagos,
low in a mangrove in the port.

Galápagos Flightless Cormorant Nannopterum harrisi, Isla Fernandina, Galápagos.
Obviously it doesn't need to work on its flight feathers, but insulation is critical in
the cold waters of the Humboldt Current.

Little Raven Corvus mellori, Kosciuszko National Park, NSW.
Again this bird was quite close to us, but engrossed its task.

Spinifex Pigeons Geophaps plumifera, indulging in some group preening near Alice Springs.

Many species, especially waterbirds, use an oily secretion from a gland on the back to spread on the feathers. This not only cleans but assists with waterproofing and acts as protection against fungi and bacteria, while keeping the feathers flexible.

Male Australian Darter Anhinga novaehollandiae taking preening oil from the gland at the base
of his tail, before anointing his feathers with it.

As an alternative, many birds utilise powder down, derived from special feathers which grow constantly and never moult, and whose tips crumble into a talc-like powder which is used for cleaning and conditioning.

 

These Southern Mealy Parrots (or Amazons) Amazona farinosa,  here at Blanquillo Clay Lick
in the Peruvian Amazon basin, are so named for their abundance of powder down,
‘mealy’ meaning ‘floury’.

Not all preening is done with the bill however. Many species in a range of families have a serrated edge to the claw on the middle toe, which is used to ‘comb’ those feathers which can't be reached by the bill, to remove dirt, lice and used powder down.

 

Pacific Heron Ardea pacifica, in Grenfell, NSW, scratching a part of her body which is
inaccessible to her bill. The use of the middle (front) toe is clear.

Swift Parrot Lathamus discolor scratching its face, Callum Brae NR, Canberra.
It was an exciting time when a flock of at least 60 of this beautiful but Critically Endangered
little parrot spend some weeks in this woodland reserve in suburban Canberra in May 2021.

Olive-backed Oriole Oriolus sagittatus scratching, somewhat awkwardly, in a backyard tree
in Nowra, NSW.

A Golden-headed Cisticola Cisticola exilis which emerged from its reedbed habitat
at the Jerrabomberra Wetlands in Canberra to have a good scratch.

Equally essential to a feather's well-being - and thus to its owner's - is regular bathing, to remove dust, feather particles and perhaps parasites. All birds practise this regularly, even in cold climates or weather, which tells us that cooling isn't the main purpose (though of course in some situations it can be.) 

Austral Negrito Lessonia rufa, Argentinian Patagonia. She is bathing in a stream
fed by a nearby glacier, at 50 degrees south, so staying cool is not her chief issue!

May in Canberra isn't quite that cold, but this Eastern Rosella Platycercus eximius
wasn't trying to escape the heat either.

Any shallow water can be used, from the edges of a lake...

Red-rumped Parrot pair Psephotus haematonotus, Lake Cargelligo, central NSW.

... to a small rockhole in the desert...

Crimson Chats Epthianura tricolor at Willie Rockhole, near the edge of the
Great Sandy Desert, Western Australia. This hole, unsurprisingly, was attracting
a regular parade of bathers.

 ... or even a fallen palm leaf that has caught some rain water.

Young Grey Fantail Rhipidura albiscapa in palm leaf bath, Coffs Harbour Botanic Gardens,
north coast of NSW.

However bathing isn't the passive process that these photos might suggest. The bird works to force water between the feathers, pushing the breast into the water, rocking hard from side to side and flinging water around with the wings. Water is then thrown onto the back, first with feathers raised to let the water in, then the feathers are pressed flat to squeeze the water through them. This vigorous activity can make it hard to get a decent photo, and I've never claimed photographic expertise!

Male Golden Whistler Pachycephala pectoralis, Canberra.

Silver-crowned Friarbird Philemon argenticeps in a Darwin back yard.

Australian White Ibis Threskiornis molucca, bathing at a popular human swimming
spot at Howard Springs, near Darwin.

Unlike the other bathers featured above, the friarbird in the Darwin back yard is using a small bird bath provided by the human inhabitants. This is perhaps the most important thing you can offer the birds in your yard, along with local plantings. And for reasons already explained it's important in both summer and winter. Here are a few birds enjoying the bath on offer.

Female Superb Fairywren Malurus cyaneus completely submerged (top right of the bath) in our
Canberra yard on a frosty June morning - indeed there had earlier been ice on the bath.
I took this photo from our balcony above it.

Double-barred Finches Stizoptera bichenovii and Chestnut-breasted Mannikin
Lonchura castaneothorax on the same Darwin bath featured in the friarbird photo above.

Eastern Spinebill Acanthorhynchus tenuirostris in a garden near Mount Clunie NP,
far northern NSW.

Metallic Starling Aplonis metallica at renowned bird lodge Kingfisher Park,
near Julatten in northern Queensland.

It might seem counter-intuitive initially for water birds to need to bathe in additon to their normal swimming, but it makes good sense when you consider that most water birds are well-waterproofed so must make an active effort to get the water into their feathers.

Magellanic Penguins Spheniscus magellanicus bathing in a flock, in the icy
waters of the Strait of Magellan at the very tip of South America. The roiling water
is evidence of their intense activity to get the dense oily feathers soaked.

Australian Pelican Pelecanus conspicillatus vigorously splashing at
Tidbinbilla Nature Reserve near Canberra.

A variant of this activity is leaf-bathing, where a bird hangs in foliage during or after rain, sometimes upside down, opening wings and feathers to allow the water through.

Sulphur-crested Cockatoo enjoying the rain.

It's not at all surprising that many urban birds have learned to use sprinkler hoses in the same way, flying through the spray or splashing in dripping leaves. Some will simply stand side-on to the spray, raising the wing on the sprinkler side to accept the shower.

Crested Pigeon Ocyphaps lophotes making the most of the hose in our back yard.
This is obviously fairly recently learned behaviour.

In the absence of water - but often when there is a choice too - birds will sometimes engage in a thorough dust bath, taking as much trouble to work the dust into the feathers as they do water. There seems to be no consensus as to why, but it is suggested that it might help to remove excess preening oil which might otherwise gum up the feathers, as well as perhaps playing a role in parasite removal.

House Sparrow Passer domesticus, deep in a dust bath
in a village on the island of Anchao, southern Chile.

Speckled Mousebirds Colius striatus crowding into a patch of dried mud
to conduct their dusty ablutions on Mount Kenya.

Finally there is the practice of sunning - spreading out the wings and opening the feathers in full sunshine - to assist in feather care. This one is a bit more complex as there are probably more than one purpose to it. For instance these vultures are certainly spreading out in the early morning sun, but I suspect that their major motive is to warm up before taking to the air in order to reduce the energy cost of getting such a big body aloft.

Black Vultures Coragyps atratus catching the early sun at Muyuna Lodge on the Amazon River,
northern Peru. Even in the tropics nights and early mornings can be cool.

True sunning for feather care however is quite different. I'm sure we've all got a fright at coming across a bird spread out and unresponsive on the ground (Australian Magpies are frequent practitioners), and being startled when it suddenly comes out of its stupor and hops away, perfectly healthy. Again the exact purpose has not been studied, but it seems as though it is an anti-parasite strategy. Sunshine can be fatal for fungi and bacteria, and it may force lice to leave the body, or expose themselves in moving away from the sun, where they may be more readily removed by the bird (though being in an apparent torpor probably precludes this idea!). Here are a few birds deeply engaged in their sunning. All four of the Australian birds featured were sunning in mid-summer so unlikely to be doing it for warmth.

Bar-shouldered Dove Geopelia humeralis, Kingfisher Park Lodge, north Queensland.
This one has raised its wing to allow better sun access to its flanks, a posture very
reminiscent of the Crested Pigeon in the hose above. We watched a few different birds
sunning in this spot - see the Macleay's Honeyeater below.

Common Bronzewing Pigeon Phaps chalcoptera sunning on a big granite boulder in
Namadgi NP south of Canberra.

Macleay's Honeyeater Xanthotis macleayanus enjoying the popular sunning site
at Kingfisher Park already mentioned. This bird was quite contorted.

Red Wattlebird Anthochaera carunculata sunning in the garden below our balcony.
This one really did look dead or dying for a while!

Social Flycatchers Myiozetetes similis sunning on a log in southern
Peruvian Amazonia.

And perhaps that's more than you wanted to know on the subject, but I do think we get even more enjoyment out of nature if we understand - or even just try to do so - more about what we're seeing. If so I hope I've been able to help a little with that. And I am just a little obsessed with how absolutely amazing are feathers and everything to do with them!

NEXT POSTING THURSDAY 14 APRIL

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