For the nest I used standard bird carving techniques, starting with molded and carved epoxy putty. The nest lining is also shredded silk, as is spider webbing which anchors the nest to the stone and vines. When it came time to make the eggs, instead of epoxy or wood, I used Australian opal to represent a female in the making, and sunstone from India to represent a male. Female rufous hummingbirds are colored quite differently than males. They are muted bronze-green on the back, with a white chest spotted with bronze, and rufous flanks.
Males are almost all rufous.
Opal is of course highly variable in color. Sunstone, a member of the feldspar family of minerals, is both iridescent and fairly close in color to a male rufous. In good light this stone shows, in an abstract way, hints of both the gorget and the body plumage. Actually, for my first try at the male egg I made an ammolite triplet. Ammolite is fossil ammonite shell, a truly iridescent material, which comes from only a few locations in Canada.