Hi! Your sentences are almost perfect. Here are the best versions and a short, simple explanation for each.
- Original: People help birds by making bird feeders and leaving food for them to eat.
Better: People help birds by making bird feeders and leaving food for them.
Why: "For them to eat" is not wrong, but "for them" is shorter and still clear. - Original: People help birds by making bird feeders and filling them with food.
Correct: People help birds by making bird feeders and filling them with food.
Why: This sentence is already correct. The two actions (making and filling) match in form, which is good. - Original: People help birds by leaving food in feeders.
Correct: People help birds by leaving food in feeders.
Why: This is also correct. You can say "the feeders" if you mean specific feeders, but both ways are fine.
One more tip: Always start a sentence with a capital letter and end with a period. Great job helping birds with your sentences!