Peregrine Falcon

The Peregrine falcon (Falco peregrinus) is a large, crow-sized bird of prey in the falcon family, known for its speed. Adults have a blue-grey back, white to rusty underparts finely barred with dark bands, and a black head with a dark "moustache" along the cheeks. The cere and feet are yellow, while the beak and claws are black.

Peregrine falcons measure 34 to 58 cm in length, with a wingspan of 74 to 120 cm. Females are noticeably larger than males, by up to 30%. Young birds are much browner, with streaked rather than barred underparts.

They live mostly along mountain ranges, river valleys and coastlines, and increasingly in cities. They are found nearly everywhere on Earth except extreme polar regions, very high mountains and most tropical rainforests, which makes them the world's most widespread bird of prey.

The Peregrine falcon was first described under its current scientific name by the English ornithologist Marmaduke Tunstall in 1771. The name means "wandering falcon", a reference to the migratory habits of many northern populations. The Latin word peregrinus means "one from abroad", probably because young birds were once caught while travelling rather than taken from the nest.

Their lineage is thought to have split from other falcons roughly 3 to 8 million years ago, probably in western Eurasia or Africa. Today 18 or 19 regional subspecies are accepted, which vary in appearance.

In the 1950s, 60s and 70s, pesticides such as DDT caused Peregrine falcons to become endangered over much of their range. Thinner eggshells meant fewer eggs hatched. After the pesticides were banned, populations recovered, helped by nest protection and releases to the wild.

In the UK, numbers crashed in the 1960s and have since recovered, with conservation work led by the RSPB. An estimated 1,402 breeding pairs were counted in 2011.

Peregrine falcons are famous for the stoop, a high-speed dive from a great height. They strike prey in mid-air with a clenched foot, stunning or killing it. Reliably measured speeds reach 184 km/h, and some reports claim far higher.

They eat mostly medium-sized birds, especially pigeons and doves, ducks and songbirds. In cities, feral pigeons can make up 80% or more of the diet. They hunt mostly at dawn and dusk, and in cities sometimes at night, helped by artificial light. In the UK this lets them catch night-migrating birds such as redwings and fieldfares.

A pair mates for life and returns to the same nesting spot each year. They nest in a scrape, a shallow hollow with no added material, normally on cliff edges, and now often on tall buildings or bridges. Pairs are territorial and defend the nest site, and nests are usually more than 1 km apart.

The female usually lays three to four eggs, incubated for 29 to 33 days. Chicks fledge 42 to 46 days after hatching and depend on their parents for up to two more months.

In the wild, Peregrine falcons can live up to 19 years 9 months. Mortality is high in the first year, at 59 to 70%, and falls to 25 to 32% a year in adults.

Threats include collisions with human-made objects, and larger hawks and owls may kill them. In North America and Europe, great horned owls and Eurasian eagle-owls are the most serious predators of nests.

They can carry a range of parasites and pathogens, including avian pox virus, Newcastle disease virus, a herpesvirus, some fungal and bacterial infections, tapeworms, lice, fleas and louse flies. Birds nesting in cities can pick up human-borne pathogens and heavy metals, which can be deadly for chicks.

Pesticide build-up once thinned their eggshells and caused a major decline.

This is general awareness only, not veterinary advice. If you find an injured or unwell wild animal, contact a vet or a wildlife rescue.

How fast is a Peregrine falcon?

Some sources claim over 320 km/h in a stoop, and one recording reached 389 km/h. Radar tracking has not confirmed such speeds, and the highest reliably measured is 184 km/h.

How long do Peregrine falcons live?

In the wild they can live up to nearly 20 years. Many die in their first year, but adults have a better chance of surviving each year.

Do Peregrine falcons nest in UK cities?

Yes. They nest on cathedrals, tower blocks and other tall buildings, which resemble their natural cliff ledges. Feral pigeons give them a plentiful food supply.

What do Peregrine falcons eat?

Mostly medium-sized birds such as pigeons, ducks and songbirds. They occasionally take small mammals, reptiles or insects.

Are Peregrine falcons rare in the UK?

They were hit hard by pesticides in the 1960s but have recovered. Their eggs and chicks are still targeted by illegal poachers, so unprotected nest locations are often not publicised.

The black patch below the eye is called the malar stripe. It is larger in sunnier parts of the world and seems to reduce glare.

Peregrine falcons see flicker at 129 Hz, very fast for a bird of their size and much faster than mammals.

Small bony bumps in the nostrils are thought to steer airflow away during a dive, helping them breathe. A third eyelid clears their eyes while keeping vision.

During courtship, the male passes food to the female in mid-air, and she flies upside-down to take it from his talons.

The upper beak has a notch near the tip, which lets them kill prey by severing the spine at the neck.

Roughly a fifth of the world's bird species are preyed on by Peregrine falcons somewhere.