February 23, 2011

Scientist Unlocks Mystery Of Seagull Sleep Patterns

A discovery made by a scientist who has been studying sleep in bird colonies found that seagulls learn from each other when it is safe to nod off.

The scientist found that when they feel it is safe to sleep, it results in "waves of sleep" passing through seagull colonies as the birds enter differing stages of vigilance.

This is the first time such behavior has been documented, and the findings were published in the journal Ethology.

Seagulls open and close their eyes periodically while sleeping, like many other species.  This allows the bird to monitor what is going on around them while they are resting.

"But not to the extent that they could if they were awake," Dr Guy Beauchamp of the University of Montreal, Canada told BBC.

Until now, it has not been clear what information seagulls use to decide when to sleep.

If many seagulls are sleeping, this may be a sign that it is safe to nap.  The same works as if few are sleeping, which could be a sign that a seagull may decide it will be more vulnerable to attack if it starts to snooze.

Beauchamp investigated this puzzle by studying how the sleep patterns of seagulls change over time at sites in the Bay of Fundy, New Brunswick, Canada.

He pointed out how often individual birds slept within a colony over fixed periods of time.

"Sleeping is easy to score because gulls usually sleep with their bills tucked into their [feathers]. Every minute or two, I calculated the proportion of sleeping birds in the group."

These counts revealed that gulls with more alert neighbors opened their eyes more often when they were asleep.

"So seagulls do pay attention to what their neighbors are doing, and adjust their sleep pattern accordingly," he told the BBC.

Beauchamp recorded waves of sleep passing through the colony as the gulls tended to copy the behavior of their neighbors. 

"It was not obvious if temporal waves would occur. They are predicted to occur when copying is important, but it had never been documented before," he told BBC.

Beauchamp's results add weight to a growing view among biologists that vigilance in animals is a social phenomenon.

Individual animals adjust their behavior according to their own perception, but also in response to information gleaned from the behavior of their companions.

Such behavior leads to a collective phenomenon, and in this case is waves of sleep.


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