Other
National Aviary: Curriculum: Wings to Fly
Richly illustrated interactive activity leads you through an investigation of bird wings. Includes interesting comparisons of the bones in a bird's wings with those in human arms and of the design of wings in birds versus planes.
Cornell Lab of Ornithology
Cornell Lab of Ornithology: Molting
Why do birds molt? How many times a year do they molt? When do birds molt? These questions and more are answered on this comprehensive site.