Good job noticing that sentence! Here are correct ways to say it:
- Plural (many toucans): Toucans sleep with their beaks on their backs.
- Singular (one toucan): A toucan sleeps with its beak on its back.
- More natural way to say how they sleep: Toucans often tuck their beaks under their wings when they sleep.
Why?
- Look at the subject. If you say "Toucans" (many), use plural words: "beaks" and "backs" and the pronoun "their."
- If you talk about one toucan, use singular words: "beak," "back," and the pronoun "its." Also the verb becomes "sleeps."
- The last sentence is just a natural, clearer way to describe how toucans really rest.
Short examples to remember:
- "Cats lick their paws." (many cats)
- "A cat licks its paw." (one cat)