The yellow, red, orange, and brown birds of the world assume their hues because of a pigment embedded in the keratin matrix of feathers.

这种集黄色，红色，橙色和棕色于一身的鸟类，能够呈现出如此多的色彩，得益于它的羽毛角蛋白间质里含有色素。

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The green, yellow and grey birds are originally from south America but are living wild in the south of England after being released from captivity in the 90s.

这种绿色、黄色和灰色的小鸟最初来自南美洲，但自从20世纪90年代从笼中放生以来就一直生活在英国南部的野外。

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Its big leaves are green in summer and turn yellow in autumn, birds build their house in the tree, ants climb up and down for their own lives.

大在夏天和秋天变黄的树叶是绿色的，鸟儿在树上建造他们的房子，蚂蚁爬上爬下为自我的生活。

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When he received the notice to kill his unsold chickens, Mr. Shi and co-workers grabbed the yellow birds one at a time, cut their necks and removed their feathers, then tossed the remains into one of two large, blue plastic containers for disposal.

WSJ: China Kills Market Birds as Avian Flu Deaths Rise

Although he cannot definitely rule out a direct effect by the pollution on the birds' metabolism of the yellow pigment, or its incorporation into their feathers, the correlation between a shortage of caterpillars and faded plumage is strong evidence of a link between pollution, diet and bird colour.

ECONOMIST: Great tits

Whether such birds will turn out to be yellow remains to be seen.

ECONOMIST: A genetic game of chicken