The bill, or beak, of a bird assists them in eating. Different bills are best used for different kinds of foods and feeding methods. Specific scientific families of birds eat similar foods and have similarly shaped bills. Thus, the shape of the bill is key in beginning to identify a bird correctly.
For instance, Hutton's Vireo is a small green bird with an eyering and two wingbars. In plumage, habitats, and some behaviors, it is very similar to some Empidonax flycatchers, but the bills are quite different!
Again, beginners are sometimes confused by their first Spotted Towhee, thinking it must be related to the somewhat similar-looking American Robin. But one look at the bill and a birder in-the-know will quickly see that the bills are quite different, with the robin having a generalist bill and the towhee a seed eating bill.
Gulls and terns are similar and in the same family. However, the bills of terns are sharp-pointed, the bills of gulls are strongly hooked.
An American Goldfinch--bright yellow with a black cap--has a small conical seed eating bill. Carefully observing that, one would not confuse it with the insect eating bill of the Wilson's Warbler, also bright yellow with a black cap.
Every bill of a bird can be described using standard terminology. A birder should attempt to learn these terms and the correct meaning. In this regard a textbook on ornithology would be of great use.
Characters of the bill:
In addition, some birds have other features of the bill such as gular sacs, rictal bristles, nostrils in a fleshy cere or nostrils in a tube.
Here is a web site that may be helpful:
Bird External Anatomy from an ornithology course at Eastern Kentucky University.
Future posts will discuss bill shapes more specifically.
Artwork of bird beaks used under the Creative Commons Attribution-ShareAlike license (CC-BY-SA). Author: L. Shyamal.