A melanin pigment creates the different coloured plumage of the owls


from 1978, Karell’s projects have continuously gathered observations from the field. This information largely derives from capturing and ringing breeding owls and measuring their reproductive output in their native boreal forest habitat. One of his recent projects studied an owl population captured within a 250km2 section of forest, and allowed researchers to examine numerous breeding pairs. Through scrutinising their plumage, they were able to gather various forms of data, including estimates of ages and plumage coloration. Karell has also been able to connect records held on single owls with long term, dynamic trends throughout the population, thanks to productive working relationships with a network of Finnish ornithologists. “Empirical evidence from lab studies


shows that a melanin pigment creates the different coloured plumage of the owls,” explains


Karell. “Interestingly, the


species is divisible into two main types, which are coloured reddish-brown and grey. At a genetic level, the genes


58


regulating the production of this pigment are associated with genes that regulate other physiological


in changing conditions, functions, like the


immune system, metabolic rate and several kinds of hormonal behaviours. Consequently, the colour variation witnessed in birds reveals something about the whole organism, and, moreover, the evolution of the entire species.” In a previous study, published in 2011,


the researcher


and his team were able to chart and monitor evolutionary patterns. “Colour polymorphism is thought to have evolved and now be maintained by differential sensitivity of the morphs to environmental conditions,” he says. The Finnish group’s findings indicated that snow depth was the greatest threat to owl survivability and that, when facing colder conditions,


“We found that there is strong natural selection against the reddish brown type, or colour morph, and that grey owls tended to proliferate”


Karell examined the effects of


environmental change on the genetically determined plumage colour of


the owls.


Analysing statistical data on owl populations, and considering the survivability of different colour morphs


genetic selection amongst the species tended towards a particular shade. “We found that there is strong natural


selection against the reddish brown type, or colour morph, and that grey owls tended to proliferate,” says Karell.


Insight Publishers | Projects


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