Birds of prey live at the top of the food web and they evolved two signature weapons that are the keys to their success — a hooked beak for tearing flesh and powerful feet armed with talons for seizing and killing. These are the falcons and hawks, eagles and kites, harriers and ospreys, the vultures, and — working the night shift — the owls.
A family tree with surprises
"Bird of prey" is a description of a lifestyle more than a single branch of the evolutionary tree. While some birds are more closely related, like hawks, eagles, kites, and harriers, falcons are genetically distant from hawks and eagles. The same is true for owls and New World vultures, which are both distinctly separate on the evolutionary tree. The similar hunting abilities of these birds are the result of convergent evolution, when species develop similar features or behaviors to solve a problem (in this case, how to get food).
The tools of the trade
What unites these birds is a shared toolkit for catching and eating prey.
Talons and feet are the primary weapons for hunting birds. A raptor kills mostly with its feet, driving needle-sharp talons into prey and gripping with a strength that can be lethal on contact.
The hooked bill allows birds to tear prey into pieces small enough to swallow. Falcons are equipped with a notch-and-tooth structure on the edge of the beak called the tomial tooth which they use to sever the spine of captured prey.
Keen eyesight is especially important for birds that need to spot and track small, fast-moving prey, even while they themselves are moving at high speed. These birds have large eyes packed with light-sensing cells and other features that provide their legendary visual acuity.
With little light available at night, owl eyes are even larger, light gathering tools. But they also use sound to hunt. In addition to nearly silent flight, owls have evolved keen hearing abilities. They have large ears and a flat facial disc that funnel faint animal rustlings and allow them to pinpoint a prey item in total darkness.
Although they share these general hunting features, each species has adapted to fine-tune its abilities to best fit its habitat, hunting style and food choices. While vultures ride thermals scanning (and in the New World, smelling) for dead animals, falcons strike other birds in mid-air using high-speed aerial dives called stoops.
Looking at a bird’s wings can tell you something about its hunting style: broad, plank-like wings allow eagles and vultures to soar, while short wings and a long rudder-tail works for the forest ambushers, and long pointed wings are essential for the open-country speedsters.
Environmental guardians
As top predators, birds of prey do essential work holding ecosystems in check. A single family of hawks or owls can remove huge numbers of rodents from a farm over a season; harriers and kestrels help regulate the small mammals that would otherwise strip fields and spread disease. Because predators sit at the top of the food web, they're also sensitive barometers of its health — when something is wrong lower down, the raptors are often the first to show it.
That sensitivity once nearly destroyed them. In the mid-twentieth century, the pesticide DDT spread through food chains and accumulated in birds of prey, causing them to lay eggs with shells too thin to survive incubation. Eagle, falcon, and osprey populations crashed across much of North America. The alarm raised by Rachel Carson's book, Silent Spring, helped drive the banning of DDT, and in one of conservation's great success stories, raptors have recovered — Bald Eagles are now found in thriving populations, and falcons can now be spotted nesting on skyscraper ledges.
The threats haven't vanished. Lead poisoning from ammunition fragments in carcasses still kills eagles and condors; rodenticides move up the chain to poison the very hawks and owls that control rodents (a reason to skip poison bait); and collisions, electrocution, and habitat loss take a steady toll.
Looking up
There are few better ways to feel the drama of the natural world than to watch a bird of prey at work — a hawk wheeling on a thermal, an owl melting silently between the trees at dusk. If your local birds suddenly start making a racket, look up to see if a nearby raptor has made an appearance. Your birds know danger when they see it. As a human, you can support these beautiful and important birds: protect habitat and keep poisons off the landscape.