Nature's Helicopters

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Published on: May. 2, 2008

Last revision: Dec. 8, 2010

Ruby-Throated Hummingbird

Ruby-Throated Hummingbird

energy requirements, hummingbirds have to consume about half their body weight in food every day. Nectar from flowers and artificial feeders makes up a large portion of their diet, but hummingbirds also consume large numbers of soft-bodied insects and other arthropods, including mosquitoes, gnats and spiders.

I get a couple of phone calls each year from people who report hummingbirds that appear to be drinking from fruit on trees. Actually, they are probably feeding on fruit flies attracted to the fruit. In fact, they will often defend territories around trees that prove to be an insect smorgasbord.

Masters of Flight

When European explorers first saw hummingbirds, they guessed they were a cross between an insect and a bird. Indeed, no other birds are capable of the backward and forward hovering that hummingbirds have mastered. How do they do it? The answer lies largely in their specialized flight muscles and wing structure.

Hummingbirds have extremely large chest muscles in proportion to the rest of their bodies. The supracoracoideus muscle, responsible for the upstroke in bird flight, makes up about 11.5 percent of a hummingbird’s total weight. Proportionally, that’s about five times more than in other birds. Also, the chest muscles in hummingbirds are composed purely of red muscle fibers (“dark meat”), which enable long, sustained periods of muscle activity.

The feathers on the wings of hummingbirds are also very different from other birds. The flight feathers closest to their body, called secondaries, are small, while the outer flight feathers, called primaries, are proportionally much longer than normal. This enables each wing to act somewhat like a propeller.

Unlike the mostly vertical flapping motion used by most other birds, hummingbirds beat their wings on a horizontal plane, similar to a helicopter. Their wings move backward and forward at a blinding speed, averaging around 50–70 beats per second! The tips of their wings make a figure-8 motion on each stroke. This creates just the right amount of lift to hover in place. To move forward, backward or any other direction, they change the angle of their wing stroke, creating thrust in whatever direction they want to go.

Incredible Journey

Most amazing about ruby-throated hummingbirds is their annual migration. What we think of as “our” hummingbirds actually spend about eight months of the year either migrating or spending the winter in Mexico or Central America.

In late July or early August, hummingbirds begin migrating south. The males leave first. You will likely see

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