Original: Black-capped Chickadee - Poecile atricapilla - USGS Patuxent Bird Identification InfoCenter Black-capped Chickadee Species Account - Cornell Lab of Ornithology Black-capped Chickadee Information and Photos - South Dakota Birds and Birding BirdHouses101.
Simplified: All About Birds: Black-capped Chickadee., Cornell Lab of Ornithology.