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Anonymous
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Any ornithologists out there?... i read recently that "swifts sleep on the wing" How do 'they' know that?.... can you think of a way of finding it out?
sam said:I remember a thing about sharks never sleeping because they would die if stopped swimming and swooshing water through their gills. That was followed up with an idea that they 'semi sleep' while swimming slowly. Maybe Swifts do the same sort of micro power nap. But surley they can't spend their entire lives on the wing... they nest don't they? I'd catch a brief nap then.
[Swifts'] legs have become so weak, because they are so seldom used, that the birds are helpless and easily caught once on the ground; but swifts never alight on the ground except by accident. They feed on the wing, sometimes mate on the wing [!], and even sleep on the wing. At dusk, swifts circle higher and higher until they disappear from sight. It used to be thought that they returned after dark to roost at their nests, but it is now known that those which are not incubating eggs or brooding young remain aloft until sunrise, probably cat-napping on currents of rising air between short spells of flapping to gain height.
Their flight is so effortless that swifts apparently need little rest. They probably spend more of their waking hours in the air than do any other land birds. An ancient belief had it swifts roosted in the Heavens. In recent years two lines of research have been used to show that some swifts do spend the night on the wing. One was to fix an automatic device to the entrance to the nests to register whether the birds entered or left them during the hours of darkness. The other was to go up in aeroplane and actually see the birds at night.
The swifts' short legs and small, weak feet will not support them in normal fashion. They never perch on tree branches, and few can raise themselves high enough off flat ground to give their wings play to take flight. They roost clinging up-right to vertical suefaces with their sharp toenails, propped against cliff walls, tree trunks, or chimneys by their short tails.
The fact I would advance is, that swifts tread, or copulate, on the wing; and I would wish any nice observer, that is startled at the supposition, to use his own eyes, and I think he will soon be convinced. In another class on animals, viz. the insect, nothing is so common as to see the different species of many genera in conjunction as they fly. The swift is almost continually on the wing; and as it never settles on the ground, on trees, on roofs, would seldom find opportunity for amorous rites, was it not enabled to indulge them in the air. If any person would watch these birds on a fine morning in May, as thye are sailing round at a great height from the ground, he would see, every now and then, one drop on the back of another, and both of the sink down together for many fathoms with a loud piercing shriek. This I take to be the juncture when the business of generation is carrying on.
The most aerial of all birds is the sooty tern, which is widespread throughout the tropical oceans. After leaving its nesting grounds as a youngster, it is reputed to remain aloftr continuously for 3-10 years until it is old enough to breed for the first time. Although this is impossible to prove, research suggests that it does not need to return to land to rest but, as long as there is enough food available, can stay in the air indefinitely. It does not even need to settle on the sea to feed, preferring to catch fish or squid by picking them from the surface while hovering or by seizing them in mid-air when they jump to escape underwater predators.
The most aerial land bird is the common swift, which remains airbourne for 2-4 years after fledgling, during which time it sleeps, drinks, eats and even mates on the wing. Its flight is about 70 per cent more efficient than that of other birds of cpmparable size, because it has long wings and a low body mass in relation to wing area (to reduce energy expenditure) and a shallow, forked tail that reduces drag and increases lift. Like a sooty tern, it has to come to land only when it is ready to breed.
The Lecky Mouse said:Dolphins sleep half a brain at a time,
or did I just make that up?
beakboo said:I've always found swifts to be rather frightening looking. Is it just me? They look like small demons, and I've always wondered if they were the subject of much superstition. They're so incredibly well designed for flight that they seem almost like perfect machines. :monster: