Pied raven
| Pied raven | |
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| Pied raven type specimen, shot 24 September 1869. Zoologisk Museum, Copenhagen | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Corvidae |
| Genus: | Corvus |
| Species: | C. corax |
| Subspecies: | C. corax varius morpha leucophaeus |
The pied raven (Corvus corax varius morpha leucophaeus) was a colour morph of the North Atlantic subspecies of the common raven which was only found on the Faroe Islands and has disappeared since the mid-twentieth century. It had large areas of white feathering, most frequently on the head, the wings and the belly, and its beak was light brown. Apart from that, it looked like the black ravens (morpha typicus).
The pied raven received binomial names such as Corvus leucophaeus (by Vieillot, 1817) and Corvus leucomelas (by Wagler, 1827). It is currently referred to as Corvus corax varius morpha leucophaeus.
In modern Faroese, the bird is called hvítravnur ("white raven"), older name gorpur bringu hvíti ("white-chested corbie"). Normal individuals of the subspecies varius, which is found on Iceland and the Faroe Islands, already show a tendency towards more extensive white feather bases compared with the nominate subspecies. But only on the Faroes, a mutation in the melanin metabolism would become fixed in the population, causing some birds to have about half of their feathers entirely white. While albinotic specimens sometimes occur in bird populations, the pied raven seems not to have been based on such occasional "sports", but on a constantly or at least regularly present part of the local raven population.
As these birds freely interacted and interbred with the black ones which are still found on the islands, they did not constitute a distinct subspecies. However, they illustrate two aspects of population genetics: genetic drift, which in small populations will shift allele frequencies over time (in this case, causing the occasionally occurring mutation to spread and become a permanent part of the gene pool of ravens on the Faroes), and how a new, distinct subspecies may evolve over time from a distinct part of the population. Had the black and pied ravens mated preferentially with their own morph, in time the pied part of the population might have prevailed, as its coloration probably would have provided better camouflage when preying on seabirds (most of which are also black-and-white).
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Wikipedia