Ornithology lecture (scroll down to "flight"):
http://www.usd.edu/biol/faculty/swanson/ornith/lec1_2.html
Science of flight, birds and gliders:
http://www.yale.edu/ynhti/curriculum/units/1990/7/90.07.09.x.html
Feather construction, definitions:
http://globalflyfisher.com/staff/luallen/featherb.htm
Aerodynamics of flight (scroll down to "Feathers" and then down to
"The
Mechanics of Flight in Birds"):
http://wings.ucdavis.edu/Book/Animals/instructor/birds-01.html