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Peregrine Falcon (Falco peregrinus)

peregrine falcon closeup

Life History

Although very rarely observed, the peregrine falcon is one of the more famous and popular birds in both Michigan and the world. With 18 recognized races, this species is found on all continents of the world except for Antarctica. It is a member of the Falconid family, which also includes the American kestrel, merlin, prairie falcon and gyrfalcon. The Falconids are differentiated by their long pointed wings, narrow tails, strong rapid wing beats, facial masks and notched beaks which create a tooth-like projection.

Peregrines are crow-sized, with a wingspan of 36-44 inches. Adults have slate-gray backs and barred breasts, while immature birds have brown backs and heavily streaked breasts. All peregrines have prominent cheek ("moustache") marks on either side of their head. As is true in most species of "birds of prey", the female is larger than the male: females average 32 ounces in weight, while males only average 22 ounces in weight.

These falcons require large areas of open air for hunting, and subsequently, are not found in areas that are heavily forested. The diet of the peregrine falcon includes a wide variety of small birds, including pigeons, seabirds, shorebirds and songbirds. Occasionally, they have been known to take small ducks, earning them the misleading name of "duck hawks." Peregrines hunt by diving at their prey from far above and catching them in mid-flight. During these incredible dives, called "stoops", the birds can reach speeds of 180 miles per hour.

Except in urban areas, where pigeons and starlings are available throughout most of the winter, peregrines are strictly migratory. Their occurrence in Michigan has been closely related to the abundance of small migratory birds.

Peregrine pairs mate for life, and often use the same nest site (in natural settings they are called "eyries") for many years in a row. Eyries usually occur on a ledge in high cliffs or an escarpment where the nest will be inaccessible to predators. In urban areas, peregrine pairs may nest on tall buildings or bridges, which simulate the high cliffs, including updrafts. Nest sites usually have an encompassing view of the surrounding area, and are often near or over a lake or river. A nearby gravel shoreline or shoal for bathing is also a norm. The nest consists of a shallow scrape into which three to four eggs are laid. The eggs are whitish or pinkish with bold red and/or brown spots. Incubation lasts around 33 days and the responsibility is shared by both the male and female. In Michigan, nesting at natural sites is expected to occur between April and late September.

Michigan History

Due to very specific nest site requirements and their position at the top of the food chain, peregrine falcons have never been very abundant any where in the world. A 1940 survey of eyries (nesting sites) estimated that the eastern U.S. population consisted of only 350 pairs. The upper Midwest population was estimated to be 109 pairs, before a dramatic decline in the 1950s. Historically, there were 13 known eyries in Michigan, all located in the cliffs of the Upper Peninsula (Huron Mountains, Pictured Rocks, Mackinac Island), except for some found in steep sand dunes on the Fox Islands in northern Lake Michigan. The last documented successful nesting in Michigan, before restoration began, was in 1957 at Burnt Bluff, a cliff on the Garden Peninsula in Delta County.

During the 1950s, the world population of peregrines was decimated, mostly due to the use of DDT in pesticides. When DDE, the breakdown product of DDT, accumulates in the bodies of many birds, it causes them to lay very thin-shelled eggs which break during incubation. A repeat of the 1940 survey of historically known eyries, conducted in 1964, found no breeding pairs or even single adult peregrines east of the Mississippi.

By the 1970s, DDT had been banned in both Europe and the U.S., partially due to data linking it to the decline of the peregrine falcon. In 1975, the Eastern Peregrine Recovery Team was created and charged with the task of developing a management plan to restore peregrine falcons as a nesting bird population in the eastern U.S. A program of re-introduction commenced, which has been extremely successful. By 1991, over 3000 falcons had been released throughout the U.S., including 400 in the upper Midwest. At the time restoration began, the population of peregrines in the U.S. was probably down to about 10 percent of its original size.

To date, 139 peregrine falcons have been released in Michigan, including 108 in the Upper Peninsula and 31 in urban areas. Even though there are no historically documented cases of peregrines nesting in urban areas in Michigan (they were often found in castles and cathedrals in Europe and tall buildings and bridges in east coast U.S. cities), peregrines were released in Grand Rapids and Detroit, where there would be a ready food source (pigeons and starlings) and where they would be relatively protected from predators such as the Great Horned owl.

The goal of the Michigan Department of Natural Resources' Natural Heritage Program (nongame wildlife) is to have a population of 10 nesting pairs of peregrine falcons in Michigan by the year 2000. The 1995 survey found six nesting pairs in Michigan, including two in Detroit. The 1999 surveys found nine nesting pairs in Michigan, including five in the Southeast region, one in Lansing and three in the U.P.

Federal Delisting

The year 1999 will be recognized as a milestone year for the restoration of endangered species. On August 20th, the peregrine falcon "soared" off the list of federally endangered species. This triumph is significant, due to the fact that the eastern population of peregrine falcons had been completely eliminated by the mid-1960s. Michigan's last nesting pair was near Fayette, on the northern Lake Michigan shoreline in 1957. The culprit identified as the primary source of problems was DDT. This persistent pesticide entered the food chain and accumulated in the fat tissues of several raptors. DDT caused the peregrines to lay thin-shelled eggs which frequently broke or cracked under the weight of the incubating parent.

The falcon was listed as an endangered species by the U.S. Fish and Wildlife Service in 1970. The peregrine was included in the first list of endangered species promulgated under Michigan's Endangered Species Act.

With the ban on DDT and several other hard pesticides, the stage was set for the restoration of the eastern population to begin. Restoration activities consisted of taking eggs or chicks from captive bred adults and placing them in boxes until they were ready to fledge. Restoration work began on several sites in Michigan during the mid-1980s. In addition to the historic sites in the Upper Peninsula, Grand Rapids and Detroit received and released chicks.

Experts had determined that peregrines could do very well among the tall buildings larger cities had to offer. Bolstered by successes in other cities, the urban program began. In all, over 120 chicks were raised in hack boxes and released. This effort, as well as effort in neighboring states, has led to the establishment of eight known nesting pairs of falcons in Michigan during 1999. Interestingly, the most active nests have been in the Detroit area, giving virtually hundreds of thousands of people an opportunity to view these magnificent birds. We are well on our way to achieving the state goal of 10 pairs of falcons by the year 2000.

The delisting of the peregrine by the U.S. Fish and Wildlife Service will have little effect in Michigan. The peregrine remains protected federally under the Migratory Bird Treaty Act. In Michigan, peregrines remain listed as an endangered species under state law.

The peregrine falcon and other raptors that are making comebacks prove we can recover species given the right amount of time, but they also show us just how vulnerable our natural resources are to impacts we make as residents of this planet.

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