Subject: "Albino" pine siskin
Date: Mar 3 11:35:46 2000
From: NJPharris at aol.com - NJPharris at aol.com


I remember reading about budgerigar coloration genetics in college biology,
so this may help.

A budgie's coloration (normally green with yellow head and black markings) is
the result of the interaction between two different color systems. Melanin
in the core of the feather shafts and barbs produces black (or, depending on
how the pigment granules are oriented, blue); while a separate substance
turns the outer layer of the feather shaft yellow.

Thus, the colors on a budgie are produced by the following combinations:

green on body = blue core + yellow overlay
yellow on head = white core (no melanin) + yellow overlay
black markings = black core + yellow overlay

The various nonstandard-colored budgies one sees in pet stores are produced
by genetic variations that selectively knock out parts of this system:

melanin knocked out -> yellow bird w/ no black markings;
yellow pigment knocked out -> blue bird w/ white head and black markings;
both pigments knocked out -> white bird w/ no black markings.

I would theorize that the siskin you saw was a variant (?partially) lacking
in melanin but still displaying yellow pigment.

My 2 cents US/2.9 cents Canadian

Nick Pharris
Olympia, WA
mailto: NJPharris at aol.com