How hummingbirds hover, new research

This video from the USA says about itself:

Realistic aerodynamic simulation reveals how hummingbirds hover

21 November 2014

The most detailed aerodynamic simulation of hummingbird flight conducted to date demonstrates that it achieves its aerobatic abilities through a unique set of aerodynamic forces more closely aligned to those found in flying insects than in other birds. The simulation was produced by Vanderbilt engineers working with a biologist from the University of North Carolina at Chapel Hill.

From Wildlife Extra:

Secret behind hummingbird aerobatic feats discovered

Just how tiny hummingbird[s] can hover in front of a flower before darting to another has always puzzled scientists.

But new research shows that this ability is more closely related to those found in flying insects than to other birds.

A three-dimensional aerodynamic simulation demonstrated that the tiny birds make use of unsteady airflow mechanisms to generate invisible vortices of air that produce the lift they need to hover and flit from flower to flower.

When a bird pulls its wings forward and down, tiny vortices form over the leading and trailing edges and then merge into a single large vortex, forming a low-pressure area that provides lift. The tiny hummingbird[s] further enhance the amount of lift they produce by pitching up their wings (rotate them along the long axis) as they flap.

However, unlike most birds, hummingbirds are also able to generate lift on the upstroke by inverting their wings. As the leading edge begins moving backwards, the wing beneath it rotates around so the top of the wing becomes the bottom and bottom becomes the top. This allows the wing to form a leading edge vortex as it moves backward generating positive lift.

Although hummingbirds are much larger than flying insects and stir up the air more violently as they move, the way that they fly is more closely related to insects than it is to other birds, according to the researchers. Insects like dragonflies, houseflies and mosquitoes can also hover and dart forward and back and side to side.

The new realistic simulation (see film above) demonstrates that the tiny birds make use of unsteady airflow mechanisms, generating invisible vortices of air that produce the lift they need to hover and flit from flower to flower.