Now is the time of year when I start looking closely at American Goldfinches.\u00a0 During the winter, females and males are difficult to tell apart.\u00a0 The dark on the wings is black in males and dark brown in females.\u00a0 The wing bars, particularly the upper one, are a bit more yellow in males.\u00a0 In a month, telling males from females will be easy.\u00a0 The bright yellow body and the black cap on the forehead leave no doubt that such a bird is a male in his summer finery.<\/p>\n
The transformation occurs through the process of molting, the replacement of older worn feathers, pushed out by newly formed feathers from below.\u00a0 Molting is essential because feathers, marvelously light and strong, do wear down.\u00a0 These feathers must be replaced as they abrade or flight would be difficult and insulation poor.<\/p>\n
With over 11,000 species of birds in the world, generalizations about molting are hard to make.\u00a0 Most birds do molt their contour feathers (their wing feathers, tail feathers and the large body feathers) twice a year.\u00a0 A bird usually molts all of its contour feathers in a sequenced fashion in the fall, leading to its basic plumage.\u00a0 In the spring, another molt occurs leading to the alternate plumage, the plumage of the breeding season.\u00a0 Our American Goldfinches will soon be molting into their alternate plumage.\u00a0 The spring molt is often with the head, body and sometimes tail feathers replaced.<\/p>\n
The distinction between basic plumage and alternate plumage can be dramatic as in the warblers, tanagers, and Rose-breasted Grosbeaks.\u00a0 The two plumages are similar in other birds such as gulls, sparrows, wrens, chickadees and nuthatches.\u00a0 Those birds with similar alternate and basic plumages still undergo two molts a year, despite their seemingly unchanging appearances.<\/p>\n
Molting requires a significant amount of energy.\u00a0 The only activities in a bird\u2019s life that rival the energetic cost of molting are nesting and migration.\u00a0 Each activity pushes a bird to its limit.\u00a0 No bird can do two of these three activities at once.\u00a0 A typical pattern for a migratory bird is molt into alternate plumage (often a partial molt), migrate north, nest, molt into basic plumage, and migrate south.<\/p>\n
Here are a couple of examples that demonstrate the energetic demands of molting.\u00a0 Some Peregrine Falcons breed on the arctic tundra.\u00a0 The short arctic summer is not long enough to allow the falcons to nest and then molt into basic plumage.\u00a0 After nesting, the falcons begin a molt, replacing some of their flight feathers.\u00a0 They then migrate to their wintering quarters, forced south by the deteriorating weather.\u00a0 Once in their winter quarters, they resume their molt.<\/p>\n
Yellow-breasted Buntings have a broad breeding distribution in Europe and Asia, stretching from the arctic tundra to central China.\u00a0 They winter in Southeast Asia and India.\u00a0 Like the arctic Peregrine Falcons, the brief arctic summer does not allow enough time for the buntings to nest and then molt before migration.\u00a0 Those high latitude birds migrate immediately after nesting to the lower Yangtze area of China.\u00a0 In that moderate climate, the birds undergo a complete molt and then continue their migration south on fresh feathers.\u00a0 Buntings nesting in the southern part of the breeding range have plenty of time to nest and then molt before they embark on their southward migration.<\/p>\n
Two of our local bird species transform themselves from basic to alternate plumage without molting.\u00a0 The dorsal black coloration of breeding Snow Buntings is actually present in basic-plumaged birds. As the winter proceeds, the back feathers of a Snow Bunting erode, exposing the black coloration along the middle portion of each feather.\u00a0 The black is hidden in the winter by the shingle-like arrangement of overlapping feathers.\u00a0 The white spangles on winter Eurasian Starlings are eroded in the same way, leading to the black alternate plumage.\u00a0 Ornithologists call this phenomenon molt by wear.<\/p>\n
[First published on March 16, 2014]<\/p>\n\n
Now is the time of year when I start looking closely at American Goldfinches.\u00a0 During the winter, females and males are difficult to tell apart.\u00a0 The dark on the wings is black in males and dark brown in females.\u00a0 The wing bars, particularly the upper one, are a bit more yellow in males.\u00a0 In a […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"yes","ngg_post_thumbnail":0,"footnotes":""},"categories":[430],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/649"}],"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=649"}],"version-history":[{"count":1,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/649\/revisions"}],"predecessor-version":[{"id":651,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/649\/revisions\/651"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=649"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=649"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=649"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}