The opposite of a night owl or someone who stays up considerably late. One who goes to sleep early and wakes up early.
Donna: Mike can't come to the party tonight. He goes to bed so early!
Tracy: What a day eagle!
A day in which you skip every single class and just be lazy. Most commonly following a long weekend and can become a double eagle day.
This weekend I got so smashed I had to take an eagle day on monday.