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The Descent of Man

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<strong>The</strong> two sexes <strong>of</strong> the mocking bird (Turdus<br />

polyglottus, Linn.) differ very little from each<br />

other, yet the males can easily be distinguished<br />

at a very early age from the females by showing<br />

more pure white. (46. Audubon, 'Ornith. Biography,'<br />

vol. i. p. 113.) <strong>The</strong> males <strong>of</strong> a forestthrush<br />

and <strong>of</strong> a rock- thrush (Orocetes erythrogastra<br />

and Petrocincla cyanea) have much <strong>of</strong><br />

their plumage <strong>of</strong> a fine blue, whilst the females<br />

are brown; and the nestling males <strong>of</strong> both species<br />

have their main wing and tail-feathers edged<br />

with blue whilst those <strong>of</strong> the female are<br />

edged with brown. (47. Mr. C.A. Wright, in<br />

'Ibis,' vol. vi. 1864, p. 65. Jerdon, 'Birds <strong>of</strong> India,'<br />

vol. i. p. 515. See also on the blackbird, Blyth in<br />

Charlesworth's 'Magazine <strong>of</strong> Natural History,'<br />

vol. i. 1837, p. 113.) In the young blackbird the<br />

wing- feathers assume their mature character<br />

and become black after the others; on the other<br />

hand, in the two species just named the wingfeathers<br />

become blue before the others. <strong>The</strong><br />

most probable view with reference to the cases

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