Peregrine Falcons

Peregrines Falcons are a globally-distributed bird of prey that is part of the Falconidae (falcon) family. Their scientific name, Falco peregrinus, means wandering falcon. During migration, peregrines may travel great distances. Peregrines nesting in the Arctic are known to migrate to Central and South America during the winter.

Species

Peregrines are one of 6 falcon species in the United States: 

• Gyrfalcon
• Peregrine falcon
• Prairie falcon
• Alpomodo falcon
• Merlin
• American kestrel

The peregrine, merlin, and kestrel all nest in Iowa.

Appearance

Peregrines are a crow-sized bird. Females are larger and weigh 32-34 ounces (about 2 pounds) while males weigh 18-20 ounces. From beak to tail, peregrines are 13 to 16 inches long. 

During their first year, the young falcons will have a chocolate brown plumage with streaks on the belly. After one year of age, they will obtain the adult coloration which is slate blue on the back, white under the chin with black speckling and salmon on the breast. All peregrines have a dark cap and mustache stripe under each eye.

Hunting & Diet

Peregrines can fly straight-away at 60 mph. When they fold their wings and go into a dive (stoop), they can reach speeds of up to 260 mph. 

Peregrines feed mostly on other birds such as pigeons, starlings, blackbirds, ducks, jays, doves, shorebirds, and sparrows. An adult bird eats one to two blackbird-sized birds per day. Predation by peregrines has never threatened populations of other birds.

Nesting & Family

Peregrines tend to be monogamous and maintain long-term pair bonds and nest sites are often used for many years, even as new pairs take over. 

A peregrine is usually sexually mature at 2 or 3 years of age; however, one-year-old birds have been known to nest successfully. Courtship includes aerial dives and the male presenting food to the female. Mating occurs in spring, and egg laying usually begins in early April.

Nests are simply a scrape in the dirt or gravel of a cliff ledge, building alcove, or nest structure. 

Female peregrines lay a clutch of 3 to 5 eggs. Both the male and female incubate the eggs and tend the young after hatching. Incubation is 31 to 33 days. When hatched, the young peregrines are about the size of baby chickens (2 oz.) and have a light coat of white down. Unlike chickens, peregrines are helpless for the first couple weeks. Young peregrines (eyases) can walk when 2 to 3 weeks old and start tearing their own food that the adult brings when about a month old. When they are about 6 weeks old, they begin to fly but still cannot capture their own food. After they have been flying for about a month they start catching prey. When they are 9 to 12 weeks old, they hunt and care for themselves. Males develop faster than females, and young males usually fly first.

Adulthood & Migration

Young peregrines migrate out of northern climates during winter months to the southern U.S. or further south. A female hatched in Des Moines in 1994 was captured and released 30 km south of Mexico City, Mexico in March 1995. Sixty percent of the young falcons die during their first year. If they survive the first year, they have an 80 percent chance of survival in subsequent years and may live to be 12 to 15 years old. In 2000, the oldest known falcon nesting in the Midwest was a 14 year-old female. 

• Peregrine Falcon Status in Iowa Report

Peregrine Falcon Restoration

Peregrine Falcons (Falco peregrinus) nested in Iowa until the biocide crash of the 1950s caused by pesticides like DDT, with the last confirmed nest in 1956. Peregrine falcon numbers were so low that by 1964 they were extirpated (locally extinct) from the eastern United States as a breeding bird. Iowa’s Peregrine Falcon Restoration project began in 1989 against the background of a nationwide movement to restore the bird. Iowa set an initial goal of establishing 5 breeding pairs by the year 2000 with an ultimate goal of 10 breeding pairs for a viable population. 

With the help of many partners and volunteers, Peregrines were captively raised and then released to suitable nesting sites across Iowa. The Midwestern and Great Lakes region met their goal of 20-25 breeding pairs and then made a new goal of 40 pairs. This secondary goal was met in 1994 with 61 territorial pairs and 41 successful nesting pairs. 

Iowa had only two nesting pairs in 1994, both of which were utilizing nest boxes on high-rise buildings in urban areas. It did not look like Iowa would reach its goal of five breeding pairs by 2000 without additional releases. In 1998, the Iowa DNR decided to prioritize returning falcons to their historic nesting eyries and focused on cliff-side releases as opposed to urban releases. Iowa first reached their goal of five nesting peregrine falcons in 2002 when they had six falcon territories with five of them successfully fledging young. 

The peregrine falcon was delisted as a federal endangered species in 1999, though it remained an Iowa state endangered species until 2010. 2010 also happened to be the first year Iowa had 20 successful peregrine falcon nests. In 2022 16 territorial pairs nested and produced at least 21 young!