A bird’s lifestyle is written in its wings.
Birds who fly fast and maneuver quickly, such as peregrines and swifts, have narrow pointy wings built for speed and agility. They need this equipment to capture prey in the air.
Birds who soar slowly in search of food, such as red-tailed hawks and turkey vultures, have broad wings with a lot of surface area.
Broad, blunt wings create a lot of wingtip turbulence (remember those vortices?) so soaring birds have feather slots at their wingtips. This confers two flight advantages.
First, each feather stands alone like a tiny pointy wing with a high aspect ratio (ratio of length to breadth) that’s more like a peregrine’s wing. The winglets create less turbulence and therefore less drag.
The second advantage is in the gaps. As air is forced upward between the feather slots, it expands on the upper side creating low air pressure on top and therefore more lift.
Turkey vultures are masters of slow speed flight. They turn and teeter without flapping — not even once!
The slots help them fly.