Immature gannet
Immature gannet
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Of the 9,000 species of birds in the world, 1,107 species are found within the United States, while Canada and Alaska host 686 and 521 species, respectively. And 1,118 species are found throughout tropical Mexico, despite its smaller regional size. The varied body sizes, proportions and shapes of birds

certainly span the gamut of description. But we can sometimes determine a bird’s identity and learn things about its lifestyle from simply observing its shape in silhouette. The specific shape and structure of birds’ wings is a starting point, since wings serve functional roles in birds’ daily life activities. Bird wings were adapted for specific behaviors, such as migration, pursuing prey, or attracting a mate. Select species, like long-tailed ducks and alcids, even use their wings for propulsion under water.

There are generally four basic wing shapes that are common in birds: passive and active soaring wings; elliptical shape; and high-speed wings. Eagles and vultures are classic examples of passive soaring techniques. In flight, the long tips of their primary feathers spread out like reaching fingers, creating slotted wing gaps. This wing configuration takes best advantage of warm, vertical columns of rising air that provide sustained lift.

Active soaring wings are long and narrow, allowing birds to soar or fly for longer periods without flapping. Oceanic birds, such as gulls, gannets and albatrosses, are quite dependent on wind currents to support flight. Reliable winds blowing across zones of southern oceans permit the Layson albatross to exploit small differentials between wind speeds to travel incredible distances. To expend less physical energy, the albatross makes precise altitude adjustments, seeking out optimal wind conditions.

Many birds have elliptically shaped wings. These include crows, blackbirds, sparrows and thrushes. This wing shape combines rapid takeoffs and short bursts of high-speed flight and wide maneuverability, but doesn’t sustain maximum speeds for long intervals of flight. Capable of acrobatic rolls and aerial somersaults with their elliptical wings, common ravens exemplify this category in terms of ready maneuvers. Be watching for ravens on windy days as they playfully dive, chase, and jostle with each other.

High-speed wings are long and thin in design, but are relatively shorter in length than active soaring wings. These birds are the fast fliers, such as ducks, falcons, terns and sandpipers that can maintain extended, rapid air speeds over considerable distances. Their pumping, powered manner of flight is direct and purposeful, involving constant wing-flapping motion. Check out a skyward flock of passing ducks. None of these birds will be seen lazily soaring about. And, if you’ve ever witnessed twisting masses of spiraling shorebirds coursing across an open saltmarsh, you can appreciate the concept of calibrated flock maneuvers.

Birds with small, hovering-type wings, such as hummingbirds, fit into the high-speed category, as well. With nerves and muscles specially adapted for incredibly fast movement, our summering ruby-throated hummingbirds come to mind. Hummingbirds do not flap their tiny wings up and down as other birds do; instead, they rotate the wings 180 degrees at the shoulder, enabling them to fly forward or backward and hover in one spot. Wing-beat rates typical of hummers average an amazing 53 beats per second! We are only left to marvel at their improbable long-distance migratory feats of traversing the Gulf of Mexico twice a year.