Cavity: A hollow space.
Chiseled: Carved or formed with a metal tool used to shape or chip away a solid material.
Eaves: The lower edge of a roof that extends.
Extinct: A species has been eliminated due to natural processes or human activity.
Endangered: In danger of becoming extinct in the near future.
Habitat: The local environment in which a specified organism, population or species lives. It is characterized by physical and chemical features, and the presence of certain other species.
Perch: An elevated place where a bird can rest, usually a rod or branch.
Population: A group of organisms of the same species that live in the same area at the same time. An example in Maryland is the population of bald eagles that live in and around the Blackwater National Wildlife Refuge.
Recessed: Having an area that is set back or sunken in a structure.
Roost: Rest or sleep.
Species: Organisms whose members are alike and successfully reproduce among themselves. Examples in Maryland are the green salamander and the Canada goose.
Threatened: Likely to become endangered in the near future.