Approximatley every 5 hours. This link may help. I think it depends on what the metabolic needs are and what they have eaten. Milo and berries are going to be digested much faster than whole dried corn for instance.
Twice a day makes sense and compares to every five hours. If they feed at dawn 7-8am + 5 hr = 3 pm and eat again before roosting there you GO!
10 4 Curious because last weekend had a few birds to clean, all empty, regardless of time of day. Trying to correlate a possible change in feeding time etc. Need all the help I can get to find some birds.
I think this is relative. We raise chickens and if they gorge themselves ( not good ) their crops will be full. It is better if they graze all day and not have a full crop. IF they are shot during the AM and moving and grazing the crop is more likely to be empty even though they are eating. if you shoot them in late afternoon perhaps more likely to have a full crop that is digested at night.