The peregrine falcon (Falco peregrinus) is renowned for its speed, reaching over 320 km/h (200 mph) during its characteristic hunting stoop, making it the fastest member of the animal kingdom. This medium-sized raptor has an extensive global range and can be found on every continent except Antarctica. However, peregrine falcons are unevenly distributed within their vast range. Certain areas of the world boast particularly high concentrations of these powerful birds of prey. In this article, we will examine where peregrines are found in their greatest numbers and what ecological factors underpin these population concentrations.
Cliff Nesting Behavior
Peregrines demonstrate a strong preference for nesting on cliffs, quarries, tall buildings, and other similar vertical structures. This behavior is a key driver shaping their distribution and local abundance. Peregrine falcons require sufficient height to take off and build up speed during their spectacular hunting stoops. Easy access to high vantage points allows them to spot and pursue avian prey over a wide area. Tall cliffs also afford protection from terrestrial predators. For these reasons, peregrine densities tend to be highest in regions characterized by extensive cliff formations and urban centers with many skyscrapers.
Arctic Tundra
One of the world’s premier hotspots for peregrine falcons is the tundra habitat found in the Arctic. The vast expanses of northern Alaska, Canada, and Greenland provide near ideal conditions for these falcons. The treeless tundra lacks obstructions, allowing excellent visibility for locating prey. An abundance of shorebirds, songbirds, seabirds, and waterfowl provide ample food during the summer nesting season. Rugged cliffs along coastlines and rivers offer first-rate nesting sites. Researchers have recorded peregrine densities up to 6.5 pairs per 100 km2 on parts of the Arctic tundra, exemplifying the suitability of this habitat.
Coastal Greenland
Coastal areas of west and southwest Greenland boast some of the highest peregrine densities ever documented. A 1977 survey found up to 25 occupied peregrine territories along just 100 km of coastline. In some locations, almost every suitable cliff hosted a peregrine pair. Researchers attributed this incredibly high density to optimal nesting habitat and an abundance of migratory bird prey. Similar peregrine concentrations have been recorded along coastal Alaska, northern Canada, and the Siberian tundra region of Russia.
Peregrine Population Explosion
Peregrine numbers in Greenland increased dramatically during the 20th century in response to reduced human persecution and restrictions on pesticide use. Researchers estimated 500-800 Greenland peregrine pairs in the 1940s. By 1975, the population had swelled to approximately 6,500 pairs and densities reached all-time highs. Peregrine numbers plateaued around this time as availability of prime cliff nest sites became saturated. However, Greenland still supports one of earth’s densest breeding populations of peregrines.
Temperate Coastal Regions
Outside of the Arctic zone, coastal habitats at temperate latitudes also regularly support high densities of peregrines. Sea cliffs along the Pacific shoreline of North America, for example, are dotted with peregrine nests from Mexico to Alaska. The Channel Coasts of Britain and France sustain dense peregrine populations, with over 1,000 pairs estimated just for the chalk sea cliffs of southern England. Concentrations are also high along coasts of Spain, Portugal, and Morocco.
Abundant Prey
Like the Arctic, coastal habitats provide optimal foraging conditions. Seabirds nesting on cliffs and offshore islands offer a reliable prey source. Shorebirds, waterfowl, and pigeons are also common along coasts. Migratory birds concentrating at coastal stopover sites in spring and fall are easy targets for peregrines. Hunting over water gives peregrines an advantage, since prey cannot escape by hiding in vegetation.
Minimal Human Disturbance
Peregrines favor nest sites with minimal human activity. Although quite tolerant of urban areas on migration and during winter, they typically shun active human disturbance at breeding sites. Coastal cliffs are often too steep and hazardous for high levels of human access. This relative inaccessibility allows coastal peregrines to achieve much higher densities than possible in more accessible habitats.
Urban Centers
While coastal habitats accommodate the largest peregrine populations overall, urban cities now boast some of the highest densities. Prior to the mid 1900s, peregrine falcons rarely nested in urban settings. However, they have adapted remarkably well to city life in recent decades. Scraping or ledges on tall buildings often mimic natural cliff nest sites. Cities also provide a stable food source in the form of abundant pigeons and migratory songbirds.
Eastern North America
In North America, peregrines have achieved their greatest urban success in eastern cities. Out of 27 breeding pairs present in eastern U.S. states in 1974, the population rebounded to over 600 pairs by 2000. Many now breed on skyscrapers, bridges, and smokestacks surrounded by busy urban infrastructure. The peregrine density found in northeastern U.S. cities is among the highest recorded globally. Parts of southern Ontario, Canada support a density of around 10 urban peregrine pairs per 100 km2.
European Cities
European cities with centuries-old buildings offer some of the world’s best urban peregrine habitat. Cologne, Germany hosts one of earth’s most impressive urban populations, with around 45 occupied territories in the metropolitan area. Several hundred pairs are found throughout Germany’s densely urbanized Ruhr Valley. Urban centers in the UK, Netherlands, Poland, and Scandinavia support thriving peregrine populations numbering in the hundreds of pairs. Falcons have even colonized major cities as far east as Moscow.
Limiting Factors
The availability of suitable nesting ledges influences density limits in urban areas. Competition with other urban bird species can also be a factor. Urban peregrine populations will likely continue expanding in North America and Europe as they keep colonizing cities with additionaltall buildings. However, densities will never match those of remote coastal cliffs lacking human activity.
Remote Mountains and Canyons
Rugged mountains and deep canyons with an abundance of cliff habitat provide optimal conditions for peregrines in other regions beyond coasts and cities. For example, remote river gorges in Alaska and northwestern Canada have some of the highest breeding densities in North America. The Etches Canyon along the Fraser River hosted around 90 peregrine pairs in the late 1970s, equating to a density of about 90 pairs per 100 km2.
Southwestern United States
Parts of the Colorado Plateau region in the southwestern U.S. also used to support dense peregrine populations before DDT-linked declines. Surveyors counted 65 breeding pairs along a 48 km stretch of the Green River in Utah during the 1940s. Canyons and cliffs of the Snake River in Idaho may have held up to 54 pairs at this time. While not matching historic numbers, peregrines remain relatively abundant in U.S. canyon country.
Andean Mountains of South America
The mountains and valleys of the Andean cordillera provide excellent habitat for peregrines across much of South America. Chile, Argentina, and Ecuador host thriving populations. Some Andean cliff habitats likely reach densities comparable to Alaska and Canada before peregrine declines. However, insufficient survey data makes definitive comparisons difficult. Portions of the Peruvian Andes had up to 26 pairs per 100 km of river habitat as of the late 1990s.
Southern Africa
Raptor experts consider parts of southern Africa critical habitat for peregrines. Mountainous areas of South Africa and Namibia host sizeable populations, as do the dramatic cliffs of the Zambezi River gorge along the border of Zambia and Zimbabwe. This region provides a vital wintering ground for peregrines that breed in the northern hemisphere. Prey availability is high thanks to an abundance of pigeons, doves, and swifts attracted to fig trees growing along rivers and cliffs.
High Density Sites
Some surveyed sites along the escarpment and gorges of northeast South Africa and western Mozambique have revealed remarkably high peregrine densities. Occupied peregrine territories occurred at a density of 20-35 pairs per 100 km in KwaZulu-Natal province during the 1980s. Even higher densities up to 60 pairs per 100 km were recorded at Mount Auxiliary in Zimbabwe. However, most areas have not been thoroughly surveyed.
Favorable Habitat
The rocky cliffs and deep river gorges cutting through South Africa’s highveld grasslands provide ideal habitat. Peregrines choose nest sites offering panoramic views for hunting and inaccessible recesses for nesting. An abundance of feral pigeons and doves in rural and urban areas provide prey throughout the year. Mild winters allow year-round residence. Compared to the northern hemisphere, fewer competing raptor species occupy South African habitats favored by peregrines.
Australia
Coastal and inland cliff habitats across much of Australia accommodate dense peregrine populations by continental standards. However, Australia has far fewer extensive vertical cliffs compared to other land masses. The total peregrine population is also relatively small, with probably less than 1,000 breeding pairs nationwide. Peregrines remain rare or uncommon across large portions of Australia’s interior lowlands.
Coastal Concentrations
Northern coastal regions host Australia’s biggest peregrine populations. Sea cliffs lining the north coast and offshore islands offer abundant nest sites. Large numbers of migratory shorebirds provide prey. Big coastal cities like Sydney and Brisbane support increasing numbers of urban-nesting peregrines. Inland along the Flinders Ranges, the magnificent granite cliffs within Wilpena Pound Natural Harbour sustain one of the continent’s densest breeding populations.
Sparse Interior Populations
Away from northern coasts, peregrine densities drop off significantly across Australia’s vast interior. The arid plains of the Red Centre and western Australia include only scattered pairs at widely spaced cliff outcrops. Peregrines are also nearly absent from dense forests along the east coast drainages which lack cliffs. Prey is still abundant, but nest site availability limits populations in these areas. However, peregrines sometimes adapt to nesting in trees where cliffs are unavailable.
Conclusion
While exhibiting a near worldwide distribution, peregrine falcons are far from uniformly distributed. Their reliance on vertical cliffs and bluffs generates marked regional variations in density and overall abundance. Coastal habitats, especially along Greenland and Alaska, support enormous breeding populations. Peregrines also concentrate along inland cliffs and increasingly in urban areas offering tall buildings. In contrast, lowland forests and open plains lack suitable nesting habitat and host only scattered pairs. The peregrine’s specialized nesting requirements will continue shaping its local and regional distribution patterns around the globe.
