None of us is so foolish as to think that winter is over.\u00a0 However, the spring bird migration is about to begin.\u00a0 It is likely that Red-winged Blackbirds will begin to appear in Maine before the month is over.\u00a0 March will bring Common Grackles, American Woodcock, Turkey Vultures, Eastern Phoebes and Osprey.<\/p>\n
As spring approaches, many songbirds will change from a drab winter plumage to a more gaudy breeding plumage.\u00a0 Males are much more likely to \u201cget dressed up\u201d for the breeding season.\u00a0 This change in costume is accomplished by molting of feathers.<\/p>\n
Like our fingernails, bird feathers are dead structures once they are formed.\u00a0 In fact, feathers are mostly composed of keratin, the same material that makes up our fingernails.\u00a0 As feathers are formed in special structures called follicles, various pigments are deposited as small grains in the feather that gives a feather its distinctive coloration.<\/p>\n
By far the most common type of pigment in bird feathers are the melanins.\u00a0 Melanins of different types impart black, brown and other earthy tones to a feather.\u00a0 Humans produce melanins too.\u00a0 The black skin of a person of African heritage is caused by the high concentration of melanin in the skin cells.\u00a0 Lighter-skinned humans produce melanins when exposed to strong sunlight.\u00a0 That\u2019s how we get a suntan.\u00a0 Melanins are produced by the cellular machinery of birds by recombining amino acids from the breakdown of proteins.<\/p>\n
Besides providing color to feathers, melanin has another important function in birds.\u00a0 The presence of melanin grains strengthens the feathers.\u00a0 You can probably think of a number of large birds that have black wing tips.\u00a0 Northern Gannets, Snow Geese, Tundra Swans, White Ibis, Wood Storks, American White Pelicans, and Swallow-tailed Kites are good examples.\u00a0 For a flying bird, the outer feathers of the wing experience the most stress during flight.\u00a0 The birds above are not close relatives.\u00a0 All of them have evolved black-tipped wings to reduce the wear on their outer wing feathers.\u00a0 The presence of similar structures in unrelated species is called convergence; black wing tips are an excellent example of convergence.<\/p>\n
Lots of our local birds have brilliant red, yellow and orange feathers in their breeding plumage.\u00a0 In most birds, these colors are imparted by pigments called carotenoids.\u00a0 Unlike melanins that a bird can manufacture, carotenoids cannot be made by a bird\u2019s cells.\u00a0 Rather, the carotenoids are acquired in the diet either by consuming plant material or indirectly by eating animals like caterpillars that consume plants.\u00a0 Carotenoids are made by plants.\u00a0 The brilliant yellows, reds and oranges of fall trees come from carotenoids in the leaves that are unmasked only after the green chlorophyll pigment is resorbed in the fall.\u00a0 Birds retain carotenoids from their plant food for their own decoration.<\/p>\n
The amount of carotenoids in the diet of a bird can determine how colorful that bird\u2019s breeding plumage is.\u00a0 For instance, a male House Finch typically has deep red feathers on its head, breast and rump.\u00a0 Males that are good at finding food rich in carotenoids have deep red feathers.\u00a0 Males on deficient diets are yellowish rather than red.\u00a0 Research has shown that female House Finches choose their mates based on the color of the plumage.\u00a0 Red males are preferred.\u00a0 Females seem to know that if a male is good at finding food for itself, his food-finding abilities will come in handy when it is time to feed hungry nestlings.\u00a0 Yellow male House Finches will normally not be picked as mates by females.<\/p>\n
A third type of pigments in bird feathers are called porphyrins.\u00a0 These compounds are similar to the hemoglobin molecules in our blood.\u00a0 Porphyrins generally impart reddish and brownish tones.\u00a0 These pigments are found in a number of owls.\u00a0 One characteristic of porphyrin pigments is that they fluoresce under ultraviolet light.\u00a0 Birds can see into the ultraviolet portion of the spectrum so porphyrins are likely more vivid for birds than they are for us.<\/p>\n
Eastern Bluebirds, Blue Jays and some other local birds have what appear to be blue feathers.\u00a0 However, there are no blue pigments in bird feathers.\u00a0 The appearance of blue is brought about by the particular structure of the feathers.\u00a0\u00a0 That structure allows all the different colors of visible light (all the colors of the rainbow) to enter the feather but only blue colors are reflected back out.\u00a0 All the other colors are absorbed by the feather and can\u2019t be seen.\u00a0\u00a0 So, a Blue Jay appears to be blue not because of blue pigments but by selective reflection of light.\u00a0 As I tell my students, blue color in birds is a pigment of your imagination.<\/p>\n
[Originally published on February 21, 2010]<\/p>\n\n
None of us is so foolish as to think that winter is over.\u00a0 However, the spring bird migration is about to begin.\u00a0 It is likely that Red-winged Blackbirds will begin to appear in Maine before the month is over.\u00a0 March will bring Common Grackles, American Woodcock, Turkey Vultures, Eastern Phoebes and Osprey. As spring approaches, […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[479,430],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/214"}],"collection":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/comments?post=214"}],"version-history":[{"count":5,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/214\/revisions"}],"predecessor-version":[{"id":219,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/214\/revisions\/219"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=214"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=214"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=214"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}