We Live In Costa Rica And Found A Large Gray/brown Speckled Egg On Ground. It's Heavy And Warm, So There's A Chick Inside, But What Kind? How Long After An Eggs Been Laid Before It Hatches?

Egg hatching of hawks, vultures or herons. We narrowed the type of bird that probably laid the egg down to one of the three birds mentioned in the question. Can it get too warm? We put it on top of a heating pad set on the lowest heat covered in a towel inside a covered aquarium outside. I turned it off this morning because i thought it felt too warm. However, when we found it yesterday it was pretty warm naturally then as well. It is about the same size as a large grade AA chicken egg.