One of the most difficult skills to pick up as a birdwatcher is how to identify birds in flight. You have to sort through a series of visual clues all at once, at high speed: silhouette, wing shape, how fast it flaps, and patterning. An experienced birder will take in all these and other clues that are hard to put into words — and might say something like: “Look! A hawk! Must be a Cooper’s Hawk — it has that giss.” In other words, it has all the telltale signs. But where did this bit of birdwatching slang originate? More info and transcript at BirdNote.org. Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.