As darkness falls and thoughts turn to slumber, waves of sleep wash over seagulls huddling against the elements.
This is not poetry, but a discovery made by a scientist who has been studying sleep in bird colonies.
He found that seagulls learn from each other when it is safe to nod off, resulting in "waves of sleep" passing through seagull colonies as the birds enter differing states of vigilance. This is the first time such behaviour has been documented. The work is reported in the journal Ethology.
Like many other species, seagulls open and close their eyes periodically while sleeping. That allows them to monitor what is going on around them while they are resting.
"But not to the extent that they could if they were awake," explains Dr Guy Beauchamp of the University of Montreal, Canada.
So sleeping is risky, as it makes the birds vulnerable to predators. Yet, until now, it has not been clear what information seagulls use to decide when to sleep. For example, do they base the decision on their own experiences, or do they monitor what other seagulls are doing?
If many birds are sleeping, that may be a sign that it is safe to nap; equally, if few are sleeping, a seagull may decide that it will be more vulnerable to attack if it is asleep while more vigilant group members are awake.
Dr Beauchamp investigated this puzzle by studying how the sleep patterns of seagulls (Larusspp) change over time at loafing sites in the Bay of Fundy, New Brunswick, Canada. He noted 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 neighbours opened their eyes more often while sleeping.
"So seagulls do pay attention to what their neighbours are doing, and adjust their sleep pattern accordingly," he reported.
What is more, as the gulls tended to copy the behaviour of their neighbours, Dr Beauchamp recorded waves of sleep passing through the colony, with the proportion of sleeping gulls rising and then decreasing through time.
"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 says.
Dr Beauchamp's results add weight to a growing view among biologists that vigilance in animals is a social phenomenon. Individual animals adjust their behaviour - for example by deciding when to sleep - according to their own perception, but also in response to information gleaned from the behaviour of their companions. Such behaviour then leads to a collective phenomenon, in this case waves of sleep.
This is not poetry, but a discovery made by a scientist who has been studying sleep in bird colonies.He found that seagulls learn from each other when it is safe to nod off, resulting in "waves of sleep" passing through seagull colonies as the birds enter differing states of vigilance. This is the first time such behaviour has been documented. The work is reported in the journal Ethology.
Like many other species, seagulls open and close their eyes periodically while sleeping. That allows them to monitor what is going on around them while they are resting.
"But not to the extent that they could if they were awake," explains Dr Guy Beauchamp of the University of Montreal, Canada.
So sleeping is risky, as it makes the birds vulnerable to predators. Yet, until now, it has not been clear what information seagulls use to decide when to sleep. For example, do they base the decision on their own experiences, or do they monitor what other seagulls are doing?
If many birds are sleeping, that may be a sign that it is safe to nap; equally, if few are sleeping, a seagull may decide that it will be more vulnerable to attack if it is asleep while more vigilant group members are awake.
Dr Beauchamp investigated this puzzle by studying how the sleep patterns of seagulls (Larusspp) change over time at loafing sites in the Bay of Fundy, New Brunswick, Canada. He noted 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 neighbours opened their eyes more often while sleeping.
"So seagulls do pay attention to what their neighbours are doing, and adjust their sleep pattern accordingly," he reported.
What is more, as the gulls tended to copy the behaviour of their neighbours, Dr Beauchamp recorded waves of sleep passing through the colony, with the proportion of sleeping gulls rising and then decreasing through time.
"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 says.
Dr Beauchamp's results add weight to a growing view among biologists that vigilance in animals is a social phenomenon. Individual animals adjust their behaviour - for example by deciding when to sleep - according to their own perception, but also in response to information gleaned from the behaviour of their companions. Such behaviour then leads to a collective phenomenon, in this case waves of sleep.
Until now, how species such as loggerhead sea turtles manage to migrate thousands of miles across oceans with no visual landmarks has been a mystery.
To carry out the research loggerhead hatchlings from Florida were placed in circular water containers and tethered to electronic tracking systems to monitor their swimming direction. The hatchlings were then exposed to magnetic fields which replicated the fields they would come across in two locations on the same latitude but different longitude along their migratory route. The turtles reacted to each magnetic field by swimming in the directions that would, in the real location, take them along their circular migratory route. The researchers say this shows that the hatchlings are able to determine longitude using information from the magnetic field.
