How fast does a peregrine falcon dive? Published figures differ, and each source says what kind of number it gives. Guinness World Records says a diving peregrine falcon has been estimated to reach a terminal velocity of about 320 km/h (200 mph) in ideal conditions. That figure is an estimate, not a clocked speed. Animal Diversity Web says peregrine falcons in a dive have been clocked at over 180 miles per hour and are believed able to reach up to 200 mph. A peregrine falcon hunts this way by diving down from high above.

The National Wildlife Federation says a record-setting peregrine falcon was once clocked diving at 186 miles (300 kilometers) an hour. It cites Guinness World Records and the Cornell Lab of Ornithology as its sources. Audubon says that when diving on prey a peregrine may reach speeds of well over 100 mph. In a power dive from great heights, it may possibly reach 200 mph. Peregrine falcons are most successful at catching prey if they have more height from which to start a stoop, the name for their dive.

Even the weight of a peregrine falcon is given differently. The Peregrine Fund gives 0.4 to 1.5 kg, Audubon 330 g to 1.5 kg, and National Geographic 18.8 to 56.5 ounces. North American peregrines weigh an average of 907 grams, and females are typically 40 to 50 percent heavier than males. In North America a peregrine falcon is roughly crow sized.

In the middle of the 1900s the pesticide DDT made peregrine falcon eggshells thin, and the eggs broke while the parents sat on them. The United States banned the use of DDT in 1972. In 1970 there were 39 known pairs of peregrine falcons in the lower 48 states. By August 1999 The Peregrine Fund and others had released over 4,000 captive-raised peregrine falcons in 28 states, after 28 years of effort. In 1999 the peregrine falcon was taken off the United States list of endangered species.

Scientists have also measured how far peregrines travel. In a satellite-tracking study of 61 peregrines, the birds migrated an average of 8,624 km southward and 8,247 km northward. They traveled at an average of 172 km a day southward and 198 km a day northward. The peregrines were radio tracked with the Argos satellite system. They used coastal routes, mid-continental routes and water-crossing routes, including the Davis Strait and the Caribbean Sea.

Home ranges of peregrine falcons have been estimated from 177 to 1508 square kilometers. Males and females regularly hunt up to 5 km from their nest site or territory. Three subspecies live in North America. Peale's falcon is a year-round resident of the northwest Pacific coast. The Arctic peregrine nests on the tundra and winters as far south as South America. The third is the American peregrine. Some peregrine falcons migrate and some stay in one place all year.

Words to know

• stoop: falcon's dive
• subspecies: regional variant
• estimate: careful guess
• tundra: treeless Arctic
• terminal: final