. Bulletin of the British Ornithologists' Club. Bulletin 107 Vol. 82 nificant and evidence that such are retrograde and that they do not represent progressive evolution. It is clear that in so far as depigmentation is concerned there is ample experimental evidence of its production and reversal by manipulation of. Range of variation in Mallard from the average normal drake and duck to albinism and melanism. the diet in respect of the lysine content as well as by physical agents. Since a fractional amount of lysine is vital to normal pigmentation and growth, a very sensitive balance is d
. Bulletin of the British Ornithologists' Club. Bulletin 107 Vol. 82 nificant and evidence that such are retrograde and that they do not represent progressive evolution. It is clear that in so far as depigmentation is concerned there is ample experimental evidence of its production and reversal by manipulation of. Range of variation in Mallard from the average normal drake and duck to albinism and melanism. the diet in respect of the lysine content as well as by physical agents. Since a fractional amount of lysine is vital to normal pigmentation and growth, a very sensitive balance is demonstrated. In work previously published by one of us (, 1957. loc. cif.) on similar white wing-barring in corvines. in-breeding was advanced as probably causative, and it is of course well known that in-breeding favours mutation, while the relationship between a possible lysine deficiency and white wing-barring in birds living free remains obscure. As carrion feeders. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Ornithologists' Club. London : British Ornithologists' Club
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