6. Birds unveil 'silver wings'

Source:

Walker M. Birds unveil 'silver wings'. BBC – Earth News [Internet]. 2009 Sep 21 [cited 2010 Feb 06]. Available from: http://news.bbc.co.uk/earth/hi/earth_news/newsid_8263000/8263115.stm

Structural arrangements of barbules are found in dark bird feathers that give it a silver sheen. Researchers in Canada and Spain studying the bearded vulture discovered the silver sheen present in certain species of bird feathers. They found that many large open habitat birds possessed silver wings and that smaller birds did not. The cause behind the silver sheen is not due to iridescence, but due to a feather construction. Viewing the structure of the feathers, they found that a silver feather is composed of a rachis, barbs, and barbules. The key structure that creates the silver sheen is the barbules. The barbules are transparent and twist, thus, they create a silver sheen without coherent scattering like other feathers. The barbules are extremely fragile. They can be scraped off easily. Once scraped off, the feathers do not shine silver. It is thought that silver feathers can indicate health. It also allows birds with darker feathers to show off, therefore, it helps the bird become more colorful and bright.