(adjective) Traveling or changing territories frequently, often with a restless or erratic pattern. This differs from migration, which occurs in particular seasons as birds move between defined wintering and nesting ranges along relatively predictable routes.
Birds are often nomadic in search of either food or water sources. More species are nomadic in harsh climates such as deserts or far northern regions where food may be scarce, or in specific seasons when resources are harder to find, such as during a dry summer or a harsh winter. During the breeding season, these birds find a reasonably stable area to raise their broods, but may resume nomadic patterns shortly after their young have fledged. When resources are plentiful, even the most nomadic species may remain in the same area until those resources are depleted, after which they will move on, often traveling in flocks in a cooperative effort to find better territories.
Photo – Bohemian Waxwing Flock © Bruce Guenter