Turquoise
08-19-2013, 03:20 PM
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Why do parrots have such brightly colored feathers?
Birds use their feathers for a variety of purposes. Probably the most familiar function is visual communication. The sex and age of an individual is often revealed by the intensity, quality, hue and pattern of its plumage colours. There are lots of evolutionary reasons, but now you can add one more to the list: bright pigments resist bacterial degradation.
Among birds, the parrots are unique: their bright reds, oranges and yellows are not derived from dietary carotenoids. Unlike any other group of birds, parrots synthesize their own red, orange and yellow pigments, which were named "psittacofulvins" in honor of their avian creators. Interestingly, these lipid-soluble pigments are found nowhere else; not in other birds, not in plants, nor even in plankton.
In addition to their unique pigments, most parrots are monochromatic: males, females and even juvenile birds look very much the same and the brightness of their plumage doesn't vary, regardless of diet.
Taken together, these factors suggest that their unique feather pigments serve more functions than just visual communication in parrots.
This is where Edward H. Burtt, Jr., a professor in the Zoology Department at Ohio Wesleyan University in Delaware, Ohio, comes into the story. A few years ago, he noticed that a variety feather-consuming microbes, including Bacillus licheniformis, Bacillus pumilus and other Bacillus species, are present on feathers, particularly among birds that live in salty or humid habitats. So of course, he wanted to know why those bacteria were there.
Dr Burtt's investigations showed these bacteria were eating feathers, and he also found that melanin-containing feathers are more resistant to bacterial degradation than those without melanins. A tantalizing hint was provided by another researcher's observation that green feathers from Blue-crowned Parakeets were unusually resistant to bacterial degradation.
From further experiments they found that (a)feather colour significantly affected the bacterial degradation rate: White feathers degraded more rapidly than black, blue, green and red feathers. This is consistent with their hypothesis that colourful psittacofulvin pigments reduce microbial damage to parrot feathers and(b) the presence of psittacofulvins alone is not enough to resist bacterial damage: the feathers have to contain red psittacofulvins.
This sweet little study serves as a reminder that there can be (and probably are) several evolutionary functions for specific characters, all exerting their individual influences simultaneously.
Courtsey:[Users must be registered and logged in to view attached photos or hyperlinks] guardian.com
Why do parrots have such brightly colored feathers?
Birds use their feathers for a variety of purposes. Probably the most familiar function is visual communication. The sex and age of an individual is often revealed by the intensity, quality, hue and pattern of its plumage colours. There are lots of evolutionary reasons, but now you can add one more to the list: bright pigments resist bacterial degradation.
Among birds, the parrots are unique: their bright reds, oranges and yellows are not derived from dietary carotenoids. Unlike any other group of birds, parrots synthesize their own red, orange and yellow pigments, which were named "psittacofulvins" in honor of their avian creators. Interestingly, these lipid-soluble pigments are found nowhere else; not in other birds, not in plants, nor even in plankton.
In addition to their unique pigments, most parrots are monochromatic: males, females and even juvenile birds look very much the same and the brightness of their plumage doesn't vary, regardless of diet.
Taken together, these factors suggest that their unique feather pigments serve more functions than just visual communication in parrots.
This is where Edward H. Burtt, Jr., a professor in the Zoology Department at Ohio Wesleyan University in Delaware, Ohio, comes into the story. A few years ago, he noticed that a variety feather-consuming microbes, including Bacillus licheniformis, Bacillus pumilus and other Bacillus species, are present on feathers, particularly among birds that live in salty or humid habitats. So of course, he wanted to know why those bacteria were there.
Dr Burtt's investigations showed these bacteria were eating feathers, and he also found that melanin-containing feathers are more resistant to bacterial degradation than those without melanins. A tantalizing hint was provided by another researcher's observation that green feathers from Blue-crowned Parakeets were unusually resistant to bacterial degradation.
From further experiments they found that (a)feather colour significantly affected the bacterial degradation rate: White feathers degraded more rapidly than black, blue, green and red feathers. This is consistent with their hypothesis that colourful psittacofulvin pigments reduce microbial damage to parrot feathers and(b) the presence of psittacofulvins alone is not enough to resist bacterial damage: the feathers have to contain red psittacofulvins.
This sweet little study serves as a reminder that there can be (and probably are) several evolutionary functions for specific characters, all exerting their individual influences simultaneously.
Courtsey:[Users must be registered and logged in to view attached photos or hyperlinks] guardian.com