The Angel Experiment and School's Out Forever by James Patterson
Seems that someone (we don't know who) thought it would be a good idea to meld the DNA of human children with bird DNA. Their most successful effort is Maximum Ride, the protagonist of the series. She and five other hybrids--the flock--all have wings and can fly. They escape "the school" where they were made, studied, and imprisoned, and try to find out the big "why." Why were they made, why were they made, and why won't these people leave them alone?