Fast, Secure, and Private Ad-Free Browsing

["Limited-Time Offer" <AdFreeSurfing@…>]

Fast, Secure, and Private Ad-Free Browsing

http://survay.us/B8cGdljYUxOmVuqH7Jxso1vSO8KOVY8CrIJ1SapjWQH9V8ioPw

http://survay.us/ud51CvetisSUIypDpkqGTJBfJzvxvuIVK6l8M1sMCWConWWLrA

erve courtship and territorial competition, many male hummingbirds have plumage with bright, varied coloration resulting both from pigmentation in the feathers and from prismal cells within the top layers of feathers of the head, gorget, breast, back and wings. When sunlight hits these cells, it is split into wavelengths that reflect to the observer in varying degrees of intensity, with the feather structure acting as a diffraction grating. Iridescent hummingbird colors result from a combination of refraction and pigmentation, since the diffraction structures themselves are made of melanin, a pigment, and may also be colored by carotenoid pigmentation and more subdued black, brown or gray colors dependent on melanin.

By merely shifting position, feather regions of a muted-looking bird can instantly become fiery red or vivid green. In courtship displays for one example, males of the colorful Anna's hummingbird orient their bodies and feathers toward the sun to enhance the display value of iridescent plumage toward a female of interest.

One study of Anna's hummingbirds found that dietary protein was an influential factor in feather color, as birds receiving more protein grew significantly more colorful crown feathers than those fed a low-protein diet. Additionally, birds on a high-protein diet grew yellower (higher hue) green tail feathers than birds on a low-protein diet.

Aerodynamics of flight

A female ruby-throated hummingbird hovering in mid-air

A trail of wake vortices generated by a hummingbird's flight discovered after training a bird to fly through a cloud of neutrally buoyant, helium-filled soap bubbles and recording airflows in the wake with stereo photography.
Hummingbird flight has been studied intensively from an aerodynamic perspective using wind tunnels and high-speed video cameras.

Two studies of rufous or Anna's hummingbirds in a wind tunnel used particle image velocimetry techniques to investigate the lift generated on the bird's upstroke and downstroke. The birds produced 75% of their weight support during the downstroke and 25% during the upstroke, with the wings making a "figure 8" mot

untitled-part.html

[AdFreeSurfing@…]

Added by email2trac

[AdFreeSurfing@…]

This message has 1 attachment(s)