It took all afternoon and all night, but the first chick is hatched. I was just watching the mom feed the chick at 3:40 pm on Saturday and she did indeed use the rabbit they brought to the nest a couple days ago. It makes you wonder about how they knew the egg was about to hatch, and shows that they were planning on it by storing the rabbit for the first feeding. Amazing!
One of the questions our students asked related to eagle ancestry and genetics of plumage. I haven't found anything satisfactory, however I did find a nice summary of the evolution of eagles and kites from reptiles in the PBS Nature page: http://www.pbs.org/wnet/nature/episodes/american-eagle/bald-eagles-evolutionary-ancestors/4274/