| A | B |
|---|
| terrestrial | living on or in land |
| endotherm | an organism that generates its body heat internally by its own metabolism |
| feathers | specialized outgrowths of the skin of birds |
| contour feathers | feathers that cover the body, wings, and tail of a bird |
| preen | to maintain or repair using a bill |
| preen gland | a gland located near the base of the tail that secretes oil |
| down feathers | soft feathers located beneath contour feathers |
| sternum | breastbone; bone to which flight muscles are attached |
| air sacs | the posterior and anterior structure used in respiration, resulting in only oxygenated air moving through the lungs |
| incubate | to maintain favorable conditions for hatching |
