The Flying Jewels

Few birds are as stun­ning as the bril­liant­ly iri­des­cent hum­ming­birds. These bril­liant col­ors that hum­ming­birds seem­ing­ly turn on and off at will are not col­ors made from pig­ments as are the col­ors of paint and ink. And the birds don’t turn them on and off at will, they have no con­trol over the bril­liant flash­es that we see.

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While most birds’ get the col­or of their feath­ers from pig­men­ta­tion, the hummingbird’s shim­mer­ing col­ors are formed by the struc­ture of their feath­ers. Light hits lay­ers of spe­cial prism-like cells, or dif­frac­tion grat­ings, with­in the top lay­ers of the feath­ers and is bro­ken apart; some wave­lengths are rein­forced and inten­si­fied, while oth­ers are nul­li­fied through inter­fer­ence. The result­ing col­ors can be seen only when the light is hit­ting the feath­ers at pre­cise­ly the right angle.
Inter­fer­ence col­oration is respon­si­ble for the col­ors we see at the edges of oil films float­ing on water and in the skin of soap-bub­bles – the spe­cif­ic col­or shifts when the angle of light falling on the refrac­tive mate­r­i­al shifts. This is why the iri­des­cent col­ors on a hummingbird’s neck will shift sud­den­ly from ruby red to bril­liant blue and vivid green and then just as sud­den­ly turn black or dark brown as the hum­ming­bird turns it head. 
These two images of this male Anna’s Hum­ming­bird were tak­en less than a sec­ond apart, in the first the sun was refract­ed,

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in the sec­ond the bird shift­ed just a frac­tion and we see the nat­ur­al, un-refract­ed mat­te black pig­ment col­or of the melanin in the bird’s feath­ers.

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Iri­des­cent hum­ming­bird col­ors actu­al­ly result from a com­bi­na­tion of refrac­tion and pig­men­ta­tion, since the dif­frac­tion struc­tures them­selves are made of melanin.
Each platelet can pro­duce dif­fer­ent col­ors accord­ing to the angle at which it is viewed. Thus, a gor­get, the bril­liant­ly col­ored ‘bib’ at a male hummingbird’s throat, may be ruby red when seen from one angle, but as the angle changes the gor­get shifts col­or. Thus, a hum­ming­bird can shift its posi­tion just a lit­tle, and what was once dull black or dark brown will become a blaz­ing spec­trum.
No oth­er bird has such a wide spec­trum of bril­liant iri­des­cent col­ors as do hum­ming­birds. Of course it is only the males that flash iri­des­cent, female, though attrac­tive are pale in com­par­i­son,

female Anna's Hummingbird

Hummingbird wing

The hummingbird’s wing is col­or­less and near­ly trans­par­ent

Not all melanin in hum­ming­birds is the same. For exam­ple the melanin in Allen’s and Rufous Hum­ming­birds’ pig­men­ta­tion is slight­ly dif­fer­ent and looks rusty brown instead of black.

Hummingbird gathering nectar

Female Anna’s Hum­ming­bird gath­er­ing nec­tar from a tree­top.

Look­ing like an Emer­ald in the sun, this female Ruby-throat­ed Hum­ming bird paus­es dur­ing her feed­ing run.

Female Ruby-throated Humming Bird

Ruby-throated Hummingbird

Male Ruby-throat­ed Hum­ming­bird with head turned slight­ly.

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2 Responses to The Flying Jewels

  1. LaVerne Uhte says:

    I am 90 years old and don’t get out much more to see birds in their nat­ur­al set­ting so I real­l­ly appre­ci­ate your post­ing the pic­tures. I live at The Red­woods and used to walk all around the adja­cent marsh and the dog park with my binoc­u­lars to see the birds. Thank you very much for shar­ing.

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