Half Siders - Duel Phenotype

Half siders are birds that have a dual phenotype. The plumage, size, color, sometimes even the gender, differs from the left and right sides. It seems as if two halves of different birds have been glued together, which is not far from the truth.

Half siders are one facet of the larger phenomenon of mosaicism Mosaics are organisms of patchwork phenotype and/or genotype. In aviculture, half siders are most frequently encountered in budgerigars, though they have been reported in canaries and Lady Gouldians.

Hollander has discussed half siders in many species of birds. Though of a genetic origin, half siders can not be intentionally bred. Half siders are the result of cytological accidents and are the inverse of twins. The half sider phenotype is not inheritable. A strain of half siders can not be developed.

Hybridization can be a valuable technique in aviculture. Fanciers have always delighted in the production of novel forms.

The progressive aviculturist uses hybrids to achieve specific results. The red factor canary was produced by a cross of the Venezuelan red hooded siskin(Carduelis cucullata) and the canary. The satinette in the canary, actually an ino factor, as described above, might have been the result of a cross of the canary with the lutino European green finch(Chloris chloris var.) the yellow gene was transferred to the Fischer's love bird(Agapornis fischerii) from the masked(Agapornis personata).

Many mutations in aviculture are sex linked recessives.

Clearly, hens can not be split for these traits. Sometimes the developer of such a trait reports the mutation to be an autosomal recessive. This way he can sell normal hens as high priced splits. This occurred with the rosy variety of the Bourke's neophema.

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