Can anyone give me some explanation for this? I have heard, and read, that swifts spend much time, even years, without touching down, and even sleeping on the wing. How is this possible? To me it sounds a bit like a pilot falling asleep in his cockpit during a flight. A fish can be suspended in water in one spot but anything that wants to remain airborne needs to keep moving… so how do they do it without crashing? And how can an animal that relies on daytime vision keep flying at night without crashing? Do they have any alternative method (other than vision) to guide them at night?
"A swift adapts the shape of its wings to the immediate task at hand: folding them back to chase insects, or stretching them out to sleep in flight…
Swifts spend almost their entire life in the air. During flight, they continually change the shape of their wings from spread wide to swept back. When they fly slowly and straight on, extended wings carry swifts 1.5 times farther and keep them airborne twice as long. To fly fast, swifts need to sweep back their wings to gain a similar advantage…
Swifts do not land to roost, but spend the night at 1.5 km above the ground…To measure their flight speed, Swedish scientists used radar. They found that swifts let the air blow past their wings at 8 to 10 m/s (29-36 km/h). At these air speeds, swift wings deliver maximum flight efficiency. For the swift that means more gliding and less flapping to maintain altitude…
The swifts for this study had been brought in dead or dying to seven Dutch bird sanctuaries. Swifts, when forced to land on the ground, cannot take off by themselves and will starve unless a kind and timely passer-by throws them in the air. Swifts are the most aerial of birds. They migrate annually from South Africa to Europe. Over their lifetime, swifts cover 4.5 million kilometres, a distance equal to six round trips to the moon or 100 times around the Earth. At day, swifts hunt insects; at night they ‘roost’ in flight. Swifts even mate in the air and land only lay their eggs, in nests tucked away into crevices of walls and cliffs. Swifts are not related to swallows. They are family of another well-known aerial acrobat, the hummingbird.
http://www.sciencedaily.com/releases/2007/04/070427113243.htm
It is assumed that some birds such as the Swift can enter a form of sleep while flying but as yet has not been proved. I found an article which suggests the following.
‘The following review examines the evidence for
sleep in flying birds. The daily need to sleep in most
animals has led to the common belief that birds, such as the
common swift (Apus apus), which spend the night on the
wing, sleep in flight. The electroencephalogram (EEG)
recordings required to detect sleep in flight have not been
performed, however, rendering the evidence for sleep in
flight circumstantial. The neurophysiology of sleep and
flight suggests that some types of sleep might be compatible
with flight. As in mammals, birds exhibit two types of
sleep, slow-wave sleep (SWS) and rapid eye-movement
(REM) sleep. Whereas, SWS can occur in one or both brain
hemispheres at a time, REM sleep only occurs bihemispherically.
During unihemispheric SWS, the eye connected
to the awake hemisphere remains open, a state that
may allow birds to visually navigate during sleep in flight.
Bihemispheric SWS may also be possible during flight
when constant visual monitoring of the environment is
unnecessary. Nevertheless, the reduction in muscle tone
that usually accompanies REM sleep makes it unlikely that
birds enter this state in flight. Upon landing, birds may
need to recover the components of sleep that are incompatible
with flight. Periods of undisturbed postflight
recovery sleep may be essential for maintaining adaptive
brain function during wakefulness. The recent miniaturization
of EEG recording devices now makes it possible to
measure brain activity in flight. Determining if and how
birds sleep in flight will contribute to our understanding of
a largely unexplored aspect of avian behavior and may also
provide insight into the function of sleep.’
Hope this helps
References :
1. University Ecology
2.http://www.springerlink.com/content/373128476108587x/fulltext.pdf
3.http://www.londons-swifts.org.uk/Swift%20Facts.htm
"A swift adapts the shape of its wings to the immediate task at hand: folding them back to chase insects, or stretching them out to sleep in flight…
Swifts spend almost their entire life in the air. During flight, they continually change the shape of their wings from spread wide to swept back. When they fly slowly and straight on, extended wings carry swifts 1.5 times farther and keep them airborne twice as long. To fly fast, swifts need to sweep back their wings to gain a similar advantage…
Swifts do not land to roost, but spend the night at 1.5 km above the ground…To measure their flight speed, Swedish scientists used radar. They found that swifts let the air blow past their wings at 8 to 10 m/s (29-36 km/h). At these air speeds, swift wings deliver maximum flight efficiency. For the swift that means more gliding and less flapping to maintain altitude…
The swifts for this study had been brought in dead or dying to seven Dutch bird sanctuaries. Swifts, when forced to land on the ground, cannot take off by themselves and will starve unless a kind and timely passer-by throws them in the air. Swifts are the most aerial of birds. They migrate annually from South Africa to Europe. Over their lifetime, swifts cover 4.5 million kilometres, a distance equal to six round trips to the moon or 100 times around the Earth. At day, swifts hunt insects; at night they ‘roost’ in flight. Swifts even mate in the air and land only lay their eggs, in nests tucked away into crevices of walls and cliffs. Swifts are not related to swallows. They are family of another well-known aerial acrobat, the hummingbird.
http://www.sciencedaily.com/releases/2007/04/070427113243.htm
References :
It’s a myth. They catch and eat insects on the wing.
References :