How The Dominant Crested Character Is Inherited

By the late Cyril Rogers (1985)

Although the crested varieties of budgerigars are not very often seen at local shows there is always a good display of these unusual birds at the Specialist & Rare Variety Show and the Budgerigar Society’s Club Show. Invariably I get questions about how these birds are bred and why there is a difference in the actual crests carried by individual specimens. The inheritance of the crested character is a little different to the normal way in which mutant characters are handed down and this makes their breeding extremely interesting. In the following paragraphs I will endeavour to explain in simple terms just how the dominant crested character is inherited.

First of all, I must say a few words about the origins of the crested birds. The first crested budgerigars were reported as having been bred some time during the 1920’s in Australia and examples of these birds came to Great Britain some decades later. Shortly after these birds arrived in Great Britain a further crested mutation was reported to have appeared in America in the 1940’s. During this period yet another crested mutation was reported, as having been bred in Europe but its exact origin does not seem to have been established.

Although these different crested mutations inter-breed quite successfully there is a slight difference in the actual formation of the crest feathers. It is usual to call the above mentioned mutations the American and Continental strains. As already stated, both kinds breed in the same way but they do differ a little in the site of the centre of the crest. In the Continental strain the centre is positioned just above the cere and in the American it is a little further back on the head. This positioning does alter somewhat the fall of the feathers in the crest of each strain. Because the strains have been so mixed together over the years, birds can carry the possibility of throwing both kinds.

A Dominant Character

In the beginning of crest breeding it was not fully understood just how and why the different shaped crests were produced beyond the fact that the character was a dominant one. Various theories were suggested but they did not fully explain the breeding results obtained until a further theory was put forward, known as the initiator theory. The theory showed that the formation of a crest was due to the complimentary action of two semi-dominant genes, one a crest initiating gene and the other a crest determining gene.

When both are present in a single quantity in a bird’s genetical makeup the crest produced is tufted. Should the initiating gene be present in a single quantity and the determining gene in a double quantity the crest produced is half-circular. However, when the initiating is present in a double quantity and the determining gene is there in either a single or double quantity the crest is full circular. Beside the actual crested birds there are normals, which can carry the crest forming genes and these are known as crestbreds. Although these crestbreds are visually like ordinary normals they have a decided effect on the kind of crests produced when paired to one of the crested kinds.

From these brief notes it will be seen how interesting and sometimes a little frustrating the breeding of crested budgerigars can be. Fortunately for the newcomer to crests the whole picture of their breeding is explained very carefully and fully in the latest edition of the handbook of The Crested Budgerigar Club, which can be obtained from the Secretary Mr C G Hawkins, "Homelea", Dadford, Bucks. MK18 5JX, UK. Tel. 01280-822872.

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