I agree with the Sevin statement. Nobody has chiggers like we do here- it's a evil we all live with, and they're on the rabbits, the squirrels, etc. so it has nothing to do with chickens here.
You can use Sevin on your yard and it's not going to kill the birds. You may not know this, but you can get Flowers of Sulfur at any pharmacy and put it in an old sock to dust yourself so you don't get bitten. It says not to put it on the skin, but I called Poison Control myself, and they said it's just a liability thing, that pharmacies use it in compounds FOR the skin.
You'll never be bitten again if you dust your ankles, and if you intend to sit in the grass, you dust your underwear elastics.
Fact: showering within an hour of being in a chigger-infested area will prevent chigger bites altogether.