Saturday, November 16, 2013

Really Weird Birds - The Alpine Swift

The Alpine swift is an amazing migratory bird that spends its breeding season, which is the Northern Hemisphere summer months, in and around the Mediterranean and the northern Middle East, including the United Arab Emirates, through to western Asia and India. 

Before the arrival of winter, they migrate south to southern and eastern Africa, where there is a seasonal abundance of insects.  They have wide gaping mouths perfect for catching and swallowing insects while in flight.

Alpine swift in flight. 
Recently published in the journal Nature Communications, is a study that shows the first evidence that the Alpine swift can fly day and night for 200 days straight during their migration.  This is longer than any other recorded bird.  Six birds were affixed with a device that recorded acceleration and ambient light.  This determined when the birds flapped their wings, glided, and when they rested.  The results show that they didn’t fly during their breeding season, when they had to incubate their eggs and land on the nest to feed babies.  However, they glided and flapped during their entire southern migration (which included across the Sahara Desert!).  They also glided and flapped during their entire overwintering period in sub-Saharan West Africa! Then of course the return migration was non-stop also, meaning this little bird spends more than six and a half months of non-stop, day and night flight, which covers about 6,200 miles!

Flying and staying airborne uses up a lot of energy and Alpine swifts must be able to recover and rest while still aloft.  The results from the study are still inconclusive as to whether the birds actually sleep during their time above ground.  Perhaps these birds, like some other organisms, use unihemispheric sleep, where half the brain powers down into sleep mode while the other half remains alert; or perhaps they only sleep during their breeding season. 

They are of course very well adapted to eating in the air.  They will swallow small insects, but what also nourishes them is called aerial plankton.  It’s a mixture of fungus spores, bacteria, minute seeds, and those tiny insects.  Aerial plankton also contains enough water for Alpine swifts to last them indefinitely.

This research team next hopes to discover the evolutionary causes responsible for this extraordinary behavior.

Submitted by Sara Oliver, World Bird Sanctuary Naturalist

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