Edith. Though Eliza can stay inside too. Eliza is trouble and will just get knocked up.

And yeah. Cats live years and years longer on average if they're kept indoors. (Dr. Harry, the tv vet, told me this so it must be true.) No cat diseases (though Ed already has some of those) and no cars and no other cats or dogs or coyotes helps. Ed loves you and Hawkeye and you are both home.

Or if you only want to save the birds and not Edith then the bell. But C is righter than my original suggestion.

Here be bunnies. Also cows are still cute.