Correct sentence: Toucans sleep by tucking their beaks under their wings.
Why this is better (simple):
- Use beaks (plural) to match toucans (plural).
- Say by tucking or with their beaks tucked to show how they sleep.
- Use under their wings because toucans put their beaks under their wings, not on their backs.
Other correct ways to say it:
- Toucans sleep with their beaks tucked under their wings.
- A toucan sleeps by tucking its beak under its wing.
Fun fact: Toucans tuck their beaks under their wings to stay warm and feel safe while they sleep.