If you hear birds chirping in the winter, it means they've built up enough fat reserves to survive the cold nights and have enough energy left to defend their territory. When food is scarce, they have to decide whether to spend their energy hunting for food or use it to sing. A bird sings at dawn if it has enough energy left over from keeping warm the night before.
John McNamara of the University of Bristol says, "Because birds can't predict exactly how much energy they need to survive the night, they need to build up enough fat reserves by dusk to cater for the worst-case scenario. And as most nights are not that cold, they should have enough energy reserves left over at dawn to sing."
His team trained both wild and captive robins to weigh themselves on electronic scales. They found the birds stopped singing when food started to become scarce, as the nights got colder and their fat stores diminished. When it was warmer at night, they had more fat left at dawn and were able to sing.
Mike Everett of the Royal Society for the Protection of Birds says, "It also underlines the importance of feeding robins and other small birds in our gardens during the winter? [which] really can mean the difference between life and death."
The music of the birds is glorious and the music of Dreamland is special too. We only feature three hand-picked composers in our music store. One of these is Ray Lynch, who composed our theme music. Listen to his CD, No Blue Thing.
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