The sentence you provided is mostly correct, but let's look at it carefully and see how we can improve it a little:
Original sentence: "The penguin dad warms the egg in a pouch on his feet, while the mother is off catching fish."
Grammar check:
- "Penguin dad" is understandable, but it is better to say "The father penguin" or "The male penguin" to sound clearer.
- "Warms the egg in a pouch on his feet" is correct because some penguins, like Emperor penguins, keep eggs warm on their feet under a flap of skin (called a brood pouch).
- "While the mother is off catching fish" is a good phrase, but "off" is more informal. You can say "while the mother is out catching fish" or simply "while the mother catches fish."
Improved version: "The father penguin warms the egg in a pouch on his feet, while the mother is out catching fish."
This sentence is grammatically correct and very clear.
Summary: Your sentence is good, but changing "penguin dad" to "father penguin" and "is off catching fish" to "is out catching fish" makes it clearer and a little more formal.