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Wednesday, Nov. 3, 1999
SHERLOCK HOLMES, ORNITHOLOGIST
How to read a bird's lifestyle in its feet
By MARK BRAZIL
A reflexologist will tell you that feet reveal a great deal about a person's physical state, and that cures can be administered via the feet.
A podiatrist will be able to determine from your feet how you walk, and will note any distinctive characteristics of your style of perambulation.
I have no idea what one calls a person who specializes in looking at animal feet, but there is no doubt that one can tell an enormous amount about an animal's lifestyle, just by thinking about its feet.
Give a thought to hard-hoofed horses, which run at speed over varied terrain; consider the broad padded feet of the camel that provide it with a non-sinking stability on sand; imagine the grip a rock-climbing chamois gains from its cloven hoofs or the power that a South American giant anteater can bring to bear on a termite mound with its hugely hooked clawed feet. With a little thought, the lifestyles of many mammals become evident after a look at their feet.
The same can be said of birds too. The broadly webbed feet of the ducks and geese are clearly adapted as paddles for water, and contrast strongly with the strong toes and powerful talons of the eagles and owls, which are so effective at clutching, holding and crushing. If you know the eagle's feet then it takes no great stretch of the imagination to work out that a similar foot, but equipped with pointed scales on the underside, is going to be very well adapted for catching slippery prey -- and you have the feet of the fish hawk or osprey.
Many birds have lost the fourth or hind toe, and the three forward-facing toes are small and graceful. These are the fleet of foot, the fast-running shorebirds.
At the opposite extreme are those species where the fourth, rear-pointing toe is well developed and joined by the third toe which can be rotated around so that there are two toes facing forward and two back. This arrangement, combined with a stiff supportive tail, clearly forms a strong grip and brace, ideal for tree climbing -- and these are the woodpecker's feet.
There are feet for every lifestyle. The long, strong legs of the cranes are well adapted to wading through deep marshes and streams, while the tiny legs of the swifts, with their equally tiny, needle-sharp claws, provide excellent grip when hanging to the outside of a nest, though they are seldom used otherwise.
The minute feet of the hummingbirds indicate that they too are little used; after all, any extra weight to carry would make all that hovering flight even more difficult to fuel. In contrast the enormously enlarged feet of the cormorants, which fit so closely together and which are set on surprisingly short, stout legs, work like a paddle steamer's paddle once submerged.
Certain birds have bodies no larger than a chicken, but enormously elongated toes, almost half as long as the body. The purpose of those "stretched" feet might take a little more thought to divine. Though their feet are not webbed, these birds live near water. In fact, they move about on the water. Their long thin toes help spread their weight out so much that the aquatic vegetation is able to support them. These are the lily-trotters, or jacanas.
The same patterns of feet crop up over and over in the bird world, evidence that the number of lifestyles is limited and repeated in similar environments around the globe.
Earlier this year I came across a foot type I had not examined before, and so I had to put my Sherlock Holmes hat on to try and work out the possibilities.
While making my way up toward Lake Mashu in the Akan National Park region of eastern Hokkaido last spring, I came across a freshly killed bird beside the road. The unfortunate bird had no doubt been struck by a car, but was in perfect condition, which allowed me to examine its plumage in some detail. It was only after admiring the excellent cryptic coloration of its feathering that my attention was drawn to its feet.
The bird in question was a hazel grouse, Ezo raicho, a member of the game bird group widespread in Hokkaido and occuring widely across the taiga or boreal forest belt, all the way to Scandinavia.
Larger than a quail but smaller than a chicken, the hazel grouse is a true forest species. I have encountered territorial males calling from high branches in dense coniferous forest. I have seen them whirring their way between the tree trunks when disturbed, and have on several occasions seen females leading parties of youngsters through the leaf litter.
The extraordinary high-pitched whistle of this bird is a rousing call to other males, and by blowing through the hole in a 50 yen coin I have been able to convince them that I too am a territory holder. The males become inquisitive, even aggressive, and circle me in silent fury as they try to work out how to drive away their giant competitor.
As I examined this bird's feet, it was with such thoughts of past encounters rattling around in my brain that I tried to rationalize the details. These birds spend a great deal of their time either walking about on the ground, or on tree branches, so the relatively strong toes came as no surprise. These feet were clearly made for walking.
Birds' feet are scaled, reminding us that they are, after all, derived from reptiles. (Some scientists even consider birds the last living dinosaurs.) Turning the feet over, I noticed the strange feathery flanges of scales along each side of the toes. It was almost as if the toes were hairy, and at first I was at a loss to explain why.
Grouse family members typically have short legs with strong toes, and the hazel grouse is no exception. Species such as the ptarmigang or raicho, which live in Japan high in the Japanese Alps, are no strangers to snow, and their legs are well-feathered for insulation in arctic or alpine cold. That feathering also provides extra grip for the feet.
The hazel grouse, although it does not live in very high mountain areas, is no stranger to snow. In its forested habitat, snow can be from a few centimeters to a few meters deep, and I have seen evidence that hazel grouse burrow in the snow at night to protect themselves from the wind and the cold.
Could it be that those fringes along the toes spread out as the foot descends, increasing the surface area and so reducing the amount the bird sinks into the snow? I am speculating, but it seems reasonable.
If you have any other theories that might explain the hazel grouse's strange interphalangeal fringes, or if you happen to be an expert on feet, I would be delighted to hear from you.
Send questions or comments to Mark Brazil via e-mail at firstname.lastname@example.org or via snail mail care of The Japan Times.