Peregrine Falcon, Falco peregrinus

Taxonomy and Distinguishing Characteristics

The Peregrine Falcon belongs to the order Falconiformes and is a member of the family Falconida. The scientific name of the Peregrine falcon is Falco peregrinus. The genus name falco means sickle-shaped. It is often assumed that this refers to the shape of a falcon’s wings in flight, but others believe that it describes the shape of their talons. The species name peregrinus is derived from the Latin word meaning wandering, from which the word ‘pilgrim’ also originates, and refers to the Peregrine’s habit of making long migrations and of dispersing widely from their birth sites to find new nesting territories. Falcons are built for speed, and can be distinguished by their long, pointed wings and their medium to long tails. They have quick and powerful wing beats and are much more agile than other raptors, making them masters at chasing down their prey, but they cannot soar as well as species with broader wings. Falcons are unique among raptors in that they have a notched beak, which looks like a tooth on the upper mandible. This notch is used to help sever the spinal column of their prey.

Scientists have recognized 22 sub-species of the Peregrine Falcon worldwide. The three North American subspecies vary considerably in appearance and are described below.

Tundra (Artic) subspecies (Falco peregrinus tundrius)
The Tunda Peregine is the palest of the North American subspecies, and is slightly smaller than the others. Adults have an almost unmarked white breast and relatively light barring across their white belly. Their back is slate-colored with a bluish-gray tinge. The moustache on Tundra Peregrines is very narrow with white patches behind and below the eyes.

Anatum (Continental) subspecies (Falco peregrinus anatumi)
The Anatum Peregine is intermediate in color and size. It has a salmon or peach tinged breast, with stronger barring across the belly. The back is slightly darker than the Tundra Peregrine, but still has a bluish-gray tinge. The moustache on the Anatum Peregrine is very wide with small white patches behind and below the eyes.

Peale’s subspecies (Falco peregrinus pealei)
The Peale’s Peregrine is the largest and darkest of the North American subspecies. Adults have dark dense barring across the belly, and even to some degree over the breast. The moustache is slightly narrower than that of the Anatum , and unlike the other subspecies, the Peale’s has dark streaking behind and below the eye. The Peale’s Peregrine is found in the northwest Pacific region of the United States and Canada.

The Peregrine Falcon research featured on this software focuses on the Tundra Peregrine. Thus, the remainder of this description applies primarily to this sub-species.

Q: In what ways are the wing shape and beak of falcons adaptive?

Distribution
The breeding range of the Tundra Peregrine can be seen in blue in the range map below. As the name suggests, Tundra Peregrines nest in the American Artic and regions of Greenland. Our studies have shown Tundra Peregrines to winter from Delaware Bay, on the Atlantic Coast, then south throughout the southern United States, and into Central and South America. Some have been found to winter as far south as Buenos Aires, Argentina.

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Migration
Tundra Peregrines migrate twice each year between their wintering range in southern North America and in South America and the breeding range in the Artic. The fall migration begins in late August in the arctic and ends anywhere from late October to December, depending on how far south they migrate. Birds flying as far south as Argentina may not arrive until mid-December. During the fall migration, many Peregrines can be seen along the Atlantic coast of the United States, and at a concentration point on Padre Island on the Gulf Coast of Texas.

The spring migration begins in mid April and ends by early June, with Padre Island being the only major concentration point on their journey north.

Peregrines are power-flying birds rather than soaring birds, meaning they use their strong flight muscles to power their flight rather than soaring on thermals and updrafts. Because they don't require thermals to fly, they are capable of migrating at night. Males have been tracked leaving from Long Island in New York and flying non-stop to Florida.

Q: Why do peregrines that spend the winter in Argentina generally arrive on their wintering grounds later than birds that spend the winter in Florida?

Habitat
On the breeding grounds, peregrines can be found in a wide variety of open habitats, including wetlands, alpine meadows, and tundra. In all cases, Peregrines choose a site that has an isolated protected spot for nesting near good hunting grounds. Most of the time this is a cliff or rocky outcrop. They prefer ledges 15 to 60 meters above ground, with a southerly exposure, some vegetation on the ledge, and a protective overhang above. Most nests consist simply of a shallow depression scraped out by the adults; no nest materials are added.

The size of a breeding territory varies greatly among individual Peregrines. In some cases nests may be within less than one kilometer of each other, while in other places a pair will defend a territory with a radius of 20 kilometers or more. The number of nests in an area is primarily related to the amount of food available.

The wintering range of the peregrine is still under investigation, but it appears that coastal regions in Central and South America with large populations of shore birds are their favorite haunts. In almost all cases there is some source of water nearby where there are plenty of small birds for the Peregrines to hunt.

Q: Draw a picture showing the characteristics of the ideal nesting habitat for a peregrine.

Hunting and Food

Hunting
Peregrines generally hunt by stooping on their prey from great heights. They fold their wings to their sides and dive toward their prey, attaining speeds of up to 320 Km/h. They keep all of their toes fully extended, and strike either with their talons or with the back of their legs. The impact is usually forceful enough to kill the prey instantly, and the Peregrine either stoops down to catch it as it tumbles, or picks it up off the ground where it lands. They use their notched beak to sever the spinal cord of their prey.

Food
Most Peregrines eat birds almost exclusively, although fledglings are often observed chasing and catching large flying insects such as dragonflies. Dozens of species of birds have been recorded as prey, ranging in size from chickadees and goldfinches to pigeons, ducks, and gulls. While on migration, many Peregrines primarily hunt shorebirds.

Q: How do peregrines use their wings, legs, talons, and beaks to hunt down their prey?

Courtship Behavior and Breeding
Peregrines generally mate for life, but will readily accept a new partner if their mate dies. In most cases, Peregrines engage in courtship rituals every spring. Males court the females with acrobatic flights and repeated calls. Courtship feeding is often observed, where the male will catch prey and present it to the female. This strengthens the pair bond and gives the female a nutritional boost to lay healthy eggs, since she is too heavy to hunt efficiently on her own just prior to egg laying. An average nest attempt produces three or four eggs. Incubation usually lasts 33 to 35 days from the date the last egg was laid. Typically, the female sits on the eggs throughout the night and much of the day. The male takes over for several short shifts through the day so the female can feed. Peregrine chicks grow very rapidly. By the time they are six weeks old, they have already grown to full adult size and are starting to fly.

Q: How many weeks does it take from the beginning of incubation until the young fledge (begin to fly)?

Conservation Status
Historically, Peregrines were renowned for having remarkably stable populations. Records are best documented for Great Britain where the breeding population remained around 800 pairs up until the Second World War. Prior to the 1940s, there were roughly 7000 Peregrines in North America and at last 8000 Peregrines in Europe. After World War II, Peregrine populations declined severely. At their lowest point in the 1970s, populations dropped to several hundred in North America and under 1000 in Europe. Over time, it became more and more evident that the organochlorine known as DDT was at least partly responsible for the decline. DDT was introduced for use as an insecticide in 1945, and quickly became one of the most heavily applied insecticides around the world.

Eventually, researchers pieced together the following explanation to account for the Peregrine’s decline. DDT was sprayed over crops, and remained on the surface of seeds for a long period of time. Birds that eat these seeds then ingested the DDT. Because DDT dissolves in fat but not in water, it accumulated in the birds' fatty tissues and could not be excreted. When Peregrines ate birds contaminated with DDT, the toxin was absorbed into their tissues. With each contaminated individual they ate, the Peregrines accumulated more DDT.

It was found that DDT disrupted the reproductive system of female birds. In some cases, they laid eggs with extremely thin and weak shells, because DDT interfered with their ability to produce enough calcium for the eggshells. In other cases it prevented them from laying eggs at all.

In the early 1970s, the future of the Peregrine looked bleak. Even though DDT was banned in Canada, the United States, and most of Europe early in the decade, residues lingered in the environment at high levels, and the population of Peregrines had fallen to extremely low numbers. Later in the decade, signs of hope began to appear as conservationists released captive-bred Peregrines into the wild. In 1977, a captive-bred Peregrine made history by raising a family in the wild. In the years since, over 4000 Peregrines have been released in North America. While many of these releases failed, some individuals did survive and established territories, and populations in many areas are now slowly increasing. The Peregrines now living in eastern North America are all either birds which have been released, or descendants of captive-bred birds.

At the present time, most subspecies of Peregrines have been taken off the endangered species list. However, threats to their populations still exist and scientists must continue to closely monitor and sometimes manage their populations to ensure their continued survival.

Q: How did peregrines accumulate so much DDT in their tissues?

References and Further Reading
Cade, T.J., J. H. Enderson, C. G. Thelander, and C. M. White. 1988. Peregrine Falcon Populations. The Peregrine Fund, Inc.

Cade, T. J. 1982. The Falcons of the World. Cornell University Press, Ithaca, New York.