Have you seen a hawk or eagle circling over head, seeming to float on the air? Passive soaring wings let birds glide on gentle air currents, using the wind as a source of lift. Unlike the constant flapping required for powered flight, birds with passive soaring wings can fly for a long time with little effort, allowing them to cover vast distances with ease.
These wings have long primary feathers that spread out. This creates slots that let the bird to catch columns of hot air and rise higher in the air. This design allows birds to ride the wind currents efficiently. With slight changes in the angle and shape of the wing, these birds can move and improve their journeys.
Birds like hawks and eagles can effortlessly soar to great heights by circling in air currents, conserving energy as they search for prey.
Cooper's Hawk
By Ken FUNAKOSHI - originally posted to Flickr as Penguin can fly, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=8857315