Send him a note thanking him for all the meat birds he's donating. Tell him they're coming over so fast that you can't cull them all in time, so you're going to get your local church/foodbank/etc coming over in the week to help you process them. 
(Being silly but seriously, if they're on your property & he isn't doing anything about it then you should take care of your property however you can.)

(Being silly but seriously, if they're on your property & he isn't doing anything about it then you should take care of your property however you can.)