The gorgeous and mysterious bird stones.
Some really nice examples of bird stones at the Royal Ontario Museum.
For comparison, here is another example currently housed at the Walters Art Museum which dates to between 1500 and 1000 BC (via the Wiki Commons, 2006.15.5):
The comprehensive study done by Moorehead shows that these ambiguous prehistoric objects are found most frequently in Western Pennsylvania, New York, Tennessee, and Kentucky, and also more northward in Indiana, Michigan, Ohio, and central Canada. Loosely resembling birds, they do not usually exceed 6 inches in length, and are most commonly made of banded slate.
While still a matter of debate, it seems most likely that these bird stones were used as a counter weight for an atlatl (throwing stick), which was used throughout the Americas. One characteristic feature of the bird stone is their flat base, which is drilled at either end. These drilled holes may have been used to attach it to the atlatl. The atlatl essentially acted as an extension of the arm, and hurled a spear with great force. The earliest evidence we have of the use of the atlatl comes from the Upper Palaeolithic, dating to approximately 40,000 years ago. To visualize how these weapons were used, see this short demonstration by Dr. Elliot Abrams, professor of archaeology at Ohio University on Youtube.
It is also possible that the bird stone was worn. One interpretation along this line of thought is that they were worn on the head of women as an indication of pregnancy, appealing to the “Thunderbird” for protection.
R. Bolliger, Microphotography of the Production of Nectar from the Sansevieria Plant, (1959)
Fragment of the face of a queen, yellow jasper, c. 1353–1336 B.C. Middle Egypt
The hummingbird has long been admired for its ability to hover in flight. The key to this behavior is the bird’s capability to produce lift on both its downstroke and its upstroke. The animation above shows a simulation of hovering hummingbird. The kinematics of the bird’s flapping—the figure-8 motion and the twist of the wings through each cycle—are based on high-speed video of actual hummingbirds. These data were then used to construct a digital model of a hummingbird, about which scientists simulated airflow. About 70% of the lift each cycle is generated by the downstroke, much of it coming from the leading-edge vortex that develops on the wing. The remainder of the lift is creating during the upstroke as the bird pulls its wings back. During this part of the cycle, the flexible hummingbird twists its wings to a very high angle of attack, which is necessary to generate and maintain a leading-edge vortex on the upstroke. The full-scale animation is here. (Image credit: J. Song et al.; via Wired; submitted by averagegrdy)