It was at this point that someone wondered if a new colour could be introduced from a different species altogether. It was already known that canaries would hybridize with other species of finch – in fact show schedules even today have a special section fro these hybrids, which are referred to as ‘mules’. Except for hybrids with the European Serin, which is involved with the origin of several continental breeds, practically all of these were believed to be sterile. This was in the early days of genetics, but the reason is probably differences in chromosome numbers.
Nonetheless, experiments were made with finches carrying various colours, especially red, and eventually it was discovered that male hybrids of the canary and the South American Red Siskin Cardualis cucullata retained some fertility. Further crosses back to canaries eventually resulted in a fully fertile canary whi9ch was capable of expressing red in its plumage.
It was soon discovered that not only the red factor had been incorporated into the red factor genome. Unlike wild canaries, Red Siskins are sexually dimorphic, and this dimorphism became established in one of the newly developed breeds. Called Dimorphics or Mosaics, these show colour points on the wings that differ in males and females.
Next week: How the canary was sent down the coal mine.
(images from wikipedia, redbarnwings.com)