Thanks for the tips! The Pi is just there to run meye as a chicken monitor with some spare IR cameras I had laying around, but maybe I should have put it to use opening the door instead. :)
I used the timer/actuator setup from this thread very successfully in my chicken coop for the last year or so, but got tired of having to adjust the timer every few weeks as the light changed. We only had one unfortunate accident, and luckily the chicken lived. I probably should have built it...