Bird topography

General anatomy
The two basic parts of a bird are referred to as underparts (ventrum, adj. ventral) and upperparts (dorsum, adj. dorsal).



Size refers to the total length of the bird from the tip of its beak to the tip of its tail. For example, the Broad-winged Hawk is 16 inches long. However, dead birds may appear longer because they were stretched out with "reasonable force" (e.g. a live Western Scrub-jay is 10 inches and a dead bird may appear to be 11½ inches).



The wingspan refers to the total length of a bird's wings from wingtip to wingtip. For example, the wingspan of the Bald Eagle is 70-90 inches long.

Plumage refers to the bird's feathers.

Parts of the head/bill
A bird's bill (or beak or rostrum, adj. rostral) is divided into two parts: lower and upper mandibles. The bill can be curved (e.g. avocets), decurved (e.g. sicklebills), curved to the left as in the wrybill (the only bird known to be like that) or as in the crossbill, their bills are criss-crossed. The top of a bird's bill is known as a culmen.

The bird's nostrils are also called nares. There are specific names for the nares, such as the cere (SEER) - found in parrots, hawks, falcons and owls or operculum (OP-err-CU-lum), which is found in pigeons.

A casque (CASK) a bony structure found on top of the head (cassowaries) or on the bill (hornbills).