- [Narrator] The bird is a gold crest.
It is the smallest bird in Europe.
She weighs no more than a teaspoon of sugar.
Her eight eggs may look tiny too, but in relation to her, they're huge.
Each one weighs 16% of her body weight.
In human terms, that would be like giving birth to eight whopping 18-pound babies.
But her tiny body can only cover two or three of her large eggs at any one time.
Bird embryos develop at around 98.6 degrees, so how will she keep them all warm?
Well, the secret of her success is revealed when we turn our standard camera off and our thermal camera on.
She has hot legs.
She's pumping extra blood through them to radiate heat, and now her actions have been caught on film for the first time.
No other bird on Earth is known to do this.