Your sentence is nearly correct but needs a little fixing for better clarity and grammar. Here's the original sentence:
Baby water birds often start out with fuzzy feathers that can easily get wet. So many water birds, like swans, practise taxiing their chicks around on their back.
Let's look at the corrections step by step:
- Word Choice: Instead of "practise" (which is British spelling), you can use "practice" for American English. But since either is okay, you can keep it if you prefer British English.
- Plural Agreement: "On their back" should be "on their backs" because birds are plural, so you say "backs."
- Verb Usage: The phrase "taxiing their chicks around on their back" is a little complex. "Taxiing" is a technical word that means moving slowly over water or land, usually for aircraft. For an 8-year-old, it's better to say "carry" or "take" their chicks on their backs.
Here's a corrected and clearer version of the sentence:
Baby water birds often start out with fuzzy feathers that can easily get wet. So many water birds, like swans, carry their chicks around on their backs.
This version is easier to understand and grammatically correct.