Avian Camouflage
Avian feathers collectively known as plumage come in different colors. These colors can function to make the birds standing out or camouflage. Avian camouflage is dependent on the correspondence of the shades and pattern of plumage to the surrounding, with or without the aid of certain factors such as molting and avian posture.
Plumage that are able to camouflage
Barred plumage-plumage with bars of light and brown pigments
Countershaded plumage- birds with dark dorsal sides and light ventral sides
Plumage of earth tone colors-blacks, browns etc
How plumage acquire their colors
Avian plumage colors are produced by biochrome pigments such as Melanin and Carotenoids. Melanin is produced by the oxidation of tyrosine in dermal cells known as melanocytes (Tickell, 2003). The long (dendritic) extensions of melanocytes make contact with feather follicles, and melanin granules are transferred into the feathers via endocytosis (qtd in Tickell, 2003). Melanin is responsible for a lot of the earth tones; these are colors such as black, brown and gray. Melanin is also responsible for the varies pattern found in birds such as spotting, striping and bared plumage. There are two types of melanin they are Eumelanins and Phaemelanins. Eumelanins produces dark brown, gray and black colors and Phaemelanins produces tans, reddish brown and some yellow colors. According to Gill (1994) color patterns occur because of inverse concentrations of eumelanins and phaemelanins. For instances, in the gray catbird the lead gray colors is as a result of eumelanin and the rusty colors of undertail is as a result of phaemelanin. Carotenoids are also responsible for camouflage, they produce particular greens. Carotenoids are mostly based on the diet of the birds. The environment can also influences the plumage colors of birds and also play a role in camouflage. Iron oxides, which are adhesive substance, that are quite common in terrestrial and aquatic environment play a role in camouflage. Birds such as the male Ptarmigan use the oxide-rich soil to camouflage themselves making them less conspicuous quickly and reversibly prior to their molting in the summer. (Delhey et al, 2007).
Contributing factors of Avian camouflage
Mottling and avian posture also play a role in camouflage. Mottling is a process whereby birds shed their plumage for new plumage. In the summer Male Rock Ptarmigan minimize the conspicuousness of their white plumage from the winter by mottling to acquire a brown cryptic plumage for the summer (Paxton, 2009). Avian posture also plays a role in camouflage. The American Bittern arranges its bill pointing towards the sky, hence lining up its body contours and the stripes on its breast with it surrounding (Mayntz, n.d).
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