Garden Warblers tuck their heads into their feathers if they are unfit, scientists discover

  • Researchers analysed the sleeping patterns of migratory Garden Warblers 
  • Thermal imaging footage revealed birds low on fat reserves nestle their heads
  • Birds in better shape sleep with their heads facing forward and untucked
  • That means they are more alert as a result and can listen out for predators

Curling up for a good night's sleep when you are feeling under the weather may be just the antidote but some birds risk their lives by snuggling up to conserve energy.

Garden warbler

Garden Warbler by Biillyboy - Wikicommons

Leonida Fusani of the University of Vienna and University of Veterinary Medicine, Austria, who was involved in the research, said: 'We discovered that migratory birds trade off safety for lower energy expenditure.

'If they sleep with their head tucked in the scapular feathers, they enter a sort of deeper sleep that is associated with lower energy consumption but exposes them to higher predation risk.

'Consequently, birds in good condition sacrifice some energy to sleep more safely with the head untucked, whereas birds in poor condition sacrifice vigilance to save energy while sleeping unsafely tucked in.' 

Researchers analysed the sleeping patterns of Garden Warblers at a stopover site in the Mediterranean.

They wanted to look at how small migratory songbirds cope with sleep deprivation.

They found that at night, Garden Warblers in a poor metabolic state slept more and exhibited less migratory restlessness than birds in good condition.

Co-author Professor Andrea Ferretti, said: 'Although there was good reason to think that birds reduce heat loss by tucking their heads in their feathers, we were surprised to see that they actually reduce their alertness when sleeping in this position.'

You can read the full article here.


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