Around here big black rat snakes love chicken coops. They eat the egg and the mice that eat the feed. I've heard of corns spending a lot of time in trees so I figured they might be raiding the nests of small birds. most of my snakes also love chicks and quail so I figured eggs aren't that far off and worth the try.
Three of my corns and a king all took eggs on their first attempt. Two others ate them on the second attempt when I put the eggs in a pile with f/t hatchlings. I'll test more of my corns when breeding season passes.
These are eggs from button quail that I breed. I also have and abundance of coturnix and chicken eggs I'm going to try on larger snakes like the retics. Once the egg got several inches down (about an inch past the last photo) there was a very audible crunching sound as the egg broke. It looks like maybe half the shell got digested and half expelled in her waste.