Great Frigatebird (Fregata minor) - "The Incredible Lightness of Being...a frigate bird"
Photographed off Daphne Island, Galápagos Islands, Ecuador
Day 3 of the Galápagos trip
NOTE: View Original Size-www.flickr.com/photos/ronfredrick/41910158730/sizes/o/
Two immature Great Frigatebirds flying playfully in formation. Note the wing positioning of the lower bird as it maximizes its flight efficiency between the 1st and 3rd photos.
===================
From Wikipedia: en.wikipedia.org/wiki/Great_frigatebird
"Frigatebirds have long narrow pointed wings and a long narrow deeply forked tail. They have the highest ratio of wing area to body mass and the lowest wing loading of any bird. This has been hypothesized to enable the birds to use marine thermals created by small differences between tropical air and water temperatures."
AB2A1663-2_fShortConCAFlkr2