- Canopy
- The upper layer of leaves and branches in a forest, where birds like the Scarlet Tanager forage high out of easy view.
- Carrion
- Dead animal flesh. It's the main food of scavengers such as the Turkey Vulture.
- Cavity nester
- A bird that nests inside a hole — in a tree, bank, or nest box. Woodpeckers, bluebirds, and Wood Ducks are cavity nesters.
- Clutch
- The full set of eggs laid and incubated together in one nesting attempt.
- Conservation status
- An assessment of how close a species is to extinction. This site uses the IUCN categories, most commonly Least Concern.
- Corvid
- A member of the crow family (Corvidae) — crows, ravens, jays, and magpies — a group famous for its intelligence.
- Covert
- A small feather that covers the base of the larger flight feathers on the wing and tail. Rows of wing coverts form a bird's wing bars.
- Crepuscular
- Active mainly at dawn and dusk, the low-light hours in between day and night.
- Crest
- A tuft of feathers on the crown that a bird can raise or lower, as seen on the Northern Cardinal, Blue Jay, and Tufted Titmouse.