Birds are the most colorful of all terrestrial vertebrates. Their coloration varies widely not only from species to species but within species. Often plumage colors differ between the sexes, between adults and their young, and from season to season. All of these different color patterns increase the challenge of identification for the birder.
Within a species, adult males often differ in color and pattern of plumage, and sometimes in size, from adult females. Male andfemale NORTHERN CARDINALS have different plumages, while juveniles resemble females.
On an individual bird, color changes occur when feathers molt, or drop from their follicles to be replaced by new feathers. In its life span a bird will molt many times. After its first molt, when it loses its natal down, the bird will attain its juvenile plumage. This will be its first plumage with contour and flight feathers. This plumage often does not resemble that of either adult and is worn briefly for a few weeks or months. For the purposes of this book the term "juvenile" is used to refer to subadult plumaged birds that may, or may not, be sexually mature.
Although in many species, such as the bunting and cardinal, the juvenile attains adult plumage after its first year. There are spicies in which it takes the juvenile longer to do this. It may take juveniles of some spicies two or more years. These individuals may expirience what are known as first, second, or even third winter or summer plumages before ataining the plumage of adult birds. The ring billed gull is one such example.
Most adult birds have two molts a year with a complete molt of all feathers after the breeding season and a partial molt in late winter/early spring in which only the head and body feathers are replaced.The late winter or early spring molt produces the brighter plumage associated with many breeding birds and is called the breeding plumage or alternate plumage. Male ducks undergo a molt just after the nesting season begins and get a fresh coat of feathers that is drab like the female's called an eclipse plumage. Fall molts produce a plumage called winter plumage, fall plumage, or basic plumage.
Some genetic variations in color and pattern can be seen among populations representing different geographical races of a species. These races are also referred to as subspecies. Some species have two or more color phases or morphs.Hybrids between species may produce birds that share some characteristics of each parent but still have a very different appearance.Birds Variations Some birds results from crosses between Golden-winged Warblers and Blue-winged Warblers and their offspring.