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More on Leucism & Albinism

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  • Nathaniel Wander
    It appears that what most bird books say about the difference between the two is, well, for the birds. Nor does the semi-professional literature seem much
    Message 1 of 2 , Feb 10, 2004
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      It appears that what most bird books say about the difference between the
      two is, well, for the birds. Nor does the semi-professional literature
      seem much more reliable. For example, the often repeated environmental vs.
      genetic distinction (leucism vs. albinism) looks to be pure bird lime.

      Both conditions are well known among vertebrates of all classes, and have
      been most systematically studied among mammals. As I'd guessed based on
      human coloration, patterns of melanin deposition among vertebrates are
      quasi-independent with regard to iris, skin and keratin-bearing
      (hair/feather/scale) tissues.

      I'm pretty sure that the iris and the epidermis arise from different
      embryological layers, so it makes sense they could melanize differently,
      but I thought the keratin-bearing tissues were epidermal, so I'm not sure
      why they would color differently from the skin, except in the case of
      bleaching. However, many organisms, notably among winter snowy-landscape
      dwelling mammals, seasonally or perennially grow out relatively or mostly
      colorless fur: arctic foxes, weasels, polar bears. And that's apparently
      the crux of leucism.

      Both leucism and albinism are genetic in origin. The general agreement is
      that leucism involves limited or absent melanin deposition in the
      keratin-bearing tissues: leucistic organisms apparently produce melanin
      normally. (Polar bears are just leucistic grizzlies with black
      noses.) Albinos, on the other hand, are faulty producers of melanin in
      general. At least one source asserted that all albinos produce at least
      some melanin, just not enough to be observed grossly.

      Nathaniel Wander
      San Francisco

      [Non-text portions of this message have been removed]
    • Floyd Hayes
      True albinos completely lack all pigments; leucistic individuals lack some but not all pigments. Albinism is always hereditary. Leucism may be hereditary or
      Message 2 of 2 , Feb 11, 2004
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        True albinos completely lack all pigments; leucistic
        individuals lack some but not all pigments. Albinism
        is always hereditary. Leucism may be hereditary or
        environmentally induced (usually related to diet).

        Many years ago I collected the classic texts on
        plumage abnormalities in birds (see citations below).
        If there are any recent comprehensive reviews, please
        let me know.

        Floyd Hayes
        Angwin, CA

        ***

        Buckley, P. A. 1982. Avian genetics. Pp. 21-110 in M.
        Petrak (ed.), Diseases of cage and aviary birds, 2nd
        ed. Lea and Febiger, Philadelphia. [pp. 65-74 discuss
        various terms]

        Deane, R. 1876. Albinism and melanism among North
        American birds. Bulletin of the Nuttall Ornithological
        Club 1:20-24.

        Gross, A. O. 1965. Melanism in North American birds.
        Bird-Banding 36:240-242.

        Gross, A. O. 1965. The incidence of albinism in North
        American birds. Bird-Banding 36:67-71.

        Hailman, J. P. 1984. On describing color abnormalities
        in birds. Florida Field Naturalist 12:36-38.

        Harrison, C. J. O. 1963. Non-melanic, carotenistic and
        allied variant plumages in birds. Bulletin of the
        British Ornithologists' Club 83:90-96.

        Harrison, C. J. O. 1963. Grey and fawn variant
        plumages. Bird Study 10:219-233.

        Rollin, N. 1962. Abnormal white, yellow and fawn
        plumages. Bulletin of the British Ornithologists' Club
        82:83-87.

        Rollin, N. 1964. Non-hereditary and hereditary
        abnormal plumage. Bird Research 2:1-44.

        Ross, C. C. 1963. Albinism among North American birds.
        Cassinia 47:2-21.

        Ross, C. C. 1973. Some additional records of albinism
        in North American birds. Cassinia 54:18-19.

        Sage, B. L. 1962. Albinism and melanism in birds.
        British Birds 55:201-225.

        Sage, B. L. 1962. The incidence of albinism and
        melanism in British birds. British Birds 56:409-416.


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