Peregrine falcons aren't one of those birds we see every day, which makes them a prized find for many birders. Spotting one soaring overhead or swooping down to catch prey is a memorable experience. 

These birds are a sight to see, and if you know where to look you may just be lucky enough to see one in action. 

They live all over the world — but they aren't very common

Peregrine falcons can be found on six of Earth's seven continents — all but Antarctica — but they aren't a commonly seen bird across nearly their entire range. One reason for their widespread range is that they travel long distances, spanning across continents, according to the National Wildlife Federation. Even their common name is a nod to their far-flung range, with "peregrine" meaning wanderer.

In Illinois, peregrine falcons are most commonly seen around Lake Michigan and large rivers and lakes, according to the Illinois Department of Natural Resources. Elsewhere in the United States, the falcons are most often seen near coastlines, river valleys and mountain ranges. They typically prefer open areas, particularly those near water. 

They are fast birds, especially when diving

Peregrine falcons are fast-flying birds, but it's when they are diving that they really show off their speed skills. Their typical cruising speed is between 24 mph and 33 mph, according to the Cornell Lab of Ornithology. They can boost their speed to as high as 67 mph when trying to catch prey, and they can reach dizzying speeds of up to 200 mph when in a dive! That makes them the fastest-diving bird on Earth!

When peregrine falcons enter a dive, they close their wings and face downward. They have been clocked at speeds of 186 mph, but it has been calculated that they are capable of reaching even greater speeds — as high as 238 mph, the Cornell Lab reports. 

They are a bird that eats birds

Many raptors eat fish or rodents and other small mammals, but not so for peregrine falcons. These birds specialize in eating other birds, and they aren't too picky. More than 450 bird species in North America have been documented as prey of the peregrine falcon, and worldwide that figure may number into the thousands, the Cornell Lab reports. 

Size is not a deterrent for these falcons — at either end of the scale. They have been known to hunt large, gangly birds like sandhill cranes as well as tiny hummingbirds. Among the most common prey for peregrines are shorebirds and waterfowl as well as pigeons and some songbirds. Besides birds, they also eat bats and occasionally rodents and fish, which they have been known to steal from other raptors. 

They typically hunt while in flight, according to the National Park Service. They fly high up in the sky and then swoop down to snatch their catch. They kill their prey by biting it in the neck. 

They were nearly extirpated from the United States

Like bald eagles, peregrine falcons nearly disappeared from the United States in the 20th century because of widespread use of the pesticide DDT, according to The Peregrine Fund. DDT was used to control insects, and when peregrine falcons and other birds ate insects that had been contaminated by it, the chemical began to accumulate in their bodies. Over time, this affected the birds' ability to nest because it caused their eggs to have thin, weak shells that did not allow chicks to properly incubate and hatch.

By the mid-1960s, no peregrine falcons were known to exist in the eastern United States and 90% of the population in the western U.S. had been lost, according to The Nature Conservancy. In 1975, there were only 324 breeding pairs of the falcons in the U.S., down from 3,875 pairs in the 1940s. In 1970, the peregrine falcon was placed on the Endangered Species List, and in 1972, the use of DDT was banned in the United States.

The banning of DDT allowed for successful conservation programs for peregrine falcons and other affected birds. Through breeding programs, more than 4,000 peregrine falcons were released in the wild between 1974 and 1997. In 1999, the peregrine falcon was removed from the Endangered Species List, and today they are a species of low concern with an estimated breeding population of 340,000 worldwide, the Cornell Lab reports. 

Their migration is one of the longest on Earth

Not all peregrine falcons migrate, but some do, and those that do have one of the longest migrations in all the world. Migratory populations of the birds travel from their arctic breeding grounds to their wintering grounds in Central America and South America each fall and then make the return trip each spring. The peregrines that travel the farthest distance sometimes travel as far as 9,000 miles each way, according to Birdfact.com.

The falcons that do migrate do so to escape harsh winter weather and ensure they have a steady food supply. Since they mostly eat other migratory birds, they, too, must migrate so they have access to food.

Their migratory journey can take several months to complete, depending on how far they must travel. They typically migrate during the day, flying for several hours at a time each day. On days when the weather is rough, they will stay put to ensure safer travels.