As the ‘threat’ of genetics and Duncker’s politics slowly fade, German academics are gradually starting to address genetic issues in the study of animal and human behaviour, and German bird-fanciers are once again excited by coloured canaries. Not only has the red canary survived a difficult and acrimonious birth, it seems to be here to stay. This might sound obvious, but other once popular canaries, like the London Fancy, are now extinct, and despite years of effort, the particular genome that produced it has proved (so far at least) impossible to re-create. Others, like the lizard, fluttered within a filoplume of extinction, but were brought back from the brink by a subset of dedicated men. As far as the red canary is concerned, past disputes over colour-feeding are almost forgotten and fanciers are looking to the future, striving not only for better, redder, brighter birds, but for new varieties as well. In the quest for a redder canary, breeders who happened upon particular genetic combinations have established an array of wonderful red mutations – variations on a theme – which range from rose-pink to almost purple.1 What’s more, by crossing the true red canary with goldfinches and other native finches they have created ever more colourful birds whose genetic origins lie not in two, but three different species. There is even a small subset of enthusiasts desperately trying to produce blue and black canaries.
What really makes a red bird red remains something of a mystery. Carotenoids are clearly important, but saying that carotenoids make birds red is equivalent to saying that electricity releases the information from a compact disc. To understand fully how a CD works, and why some CDs work in a PC and not a Macintosh (and vice versa), one needs to know something about computer design or to have the help of a computer engineer. To unravel the mystery of colour, evolutionary biologists have recently done the same and combined forces with biochemists. The most prominent of these is the Italian Riccardo Stradi, who also happens to be a bird-fancier and who has made a discovery that may explain the elusive nature of the red canary’s colour.2 The starting point of Stradi’s research was the fact, well known to bird keepers, that in captivity most red birds, like house finches, linnets, crossbills and redpolls, lose their redness during the moult and turn yellow, while others like the red siskin are much better at retaining their redness. Stradi recorded the presence and absence of different carotenoids in the feathers of wild caught birds and compared those species that turn yellow in captivity with those that don’t. The crucial difference was that red siskins can convert the common yellow dietary carotenoid, lutein, into a red carotenoid and fill their feathers with it. Lutein is superabundant in the diets of all captive finches, but crucially only the red siskin (and one or two other species) has the genetic ability to use it to retain its redness. Were he still alive, Duncker might even have been convinced by Stradi’s gene by environment interaction that produces red siskins and red canaries.
One mystery remains. If Duncker successfully transferred the vital genes that confer the physiological trick of turning lutein into red pigment from the red siskin to the canary, why aren’t red canaries as red as a red siskin? Part of the answer may lie in a discovery that Duncker himself made during his variegated canary experiments with Reich in 1924: the canary’s colour is controlled by a number of different genes. The same is also likely to be true of the red siskin’s colours. As geneticists are now well aware, most traits are controlled by several different genes and accordingly their inheritance is more complex and unpredictable than Duncker could have imagined. It is possible that not all the red siskin’s red genes were transferred to canaries. Another possibility is that even if all the responsible genes do now reside in the red canary, the environment in which they currently find themselves, the canary genome, doesn’t allow them to work in the same way as they did in their original ‘host’ – even in the presence of Carophyll. Studies of genetically engineered mice and other organisms reveal that a foreign gene in a novel genome doesn’t always behave the way it ‘should’. Despite all the media hype surrounding ‘The gene’ and the human genome project, there is still a lot we don’t know.
The final possibility is that the siskin’s red genes are, as Duncker suspected, diluted by the canary’s yellow genes – Duncker’s red– yellow battle. I sent Riccardo Stradi some feathers from red canaries that had not been colour-fed for him to study their biochemical composition. His results revealed that the red canary has inherited the red siskin’s ability to transform yellow lutein into red, but – and this is the crucial part – it still retains the canary genes for changing yellow lutein into yellow – hence the less than blood-red birds. When Duncker planned his experiments he assumed that the siskin’s red genes and the canary’s yellow genes would lie in the same position on the same chromosome so that when the two species crossed the red genes would oust the yellow ones. Stradi’s findings show that this hasn’t happened. Although the red canary has acquired the siskin’s red genes, it still has the genes that make yellow in full working order. So Duncker, it seems, was right all along.