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Spotlight On: Peregrine Falcon

peregrine falson

Although all birds are protected by the Wildlife and Countryside Act, Schedule 1 of the act gives certain species even greater protection. These are birds that are rare or are particularly sensitive to disturbance. In this post, we’re focusing on one such species, the peregrine falcon. This charismatic bird of prey has had a chequered history in the UK but is now recovering from its near-extinction in the mid-twentieth century.

Appearance

Peregrines are the UK’s largest falcons, with a dark grey back and barred white underparts. In the adults, these bars are horizontal, but juveniles have vertical brownish body markings. Both males and females have black ‘moustaches’ which contrast with their white throats. Their feet are bright yellow.

Juvenile peregrine falcon
This juvenile peregrine has vertical chest markings

As with many other birds of prey, females are larger than males. There are a number of theories as to why raptors like the peregrine have developed what is called reverse sexual dimorphism. One is that the size difference means that males and females hunt for different food so don’t compete. Alternatively, it may be to protect the female from aggressive males, or it may be that females need to be bigger to produce viable eggs.

Lifestyle

The peregrine’s diet consists mostly of medium-sized birds. Many now nest in urban centres and so have gained access to a never-ending supply of feral pigeons. But although pigeons make up about a third of urban falcons’ diet, research has shown the range of other species taken.

Urban peregrine expert Ed Drewitt has found the remains of over 100 different species at feeding sites. He has also shown that they have adapted to hunt at night by using our streetlights to catch nocturnal migrants such as woodcock, snipe, teal and even corncrake.

Urban peregrine
Peregrines are increasingly seen in urban settings

Peregrines usually perch high up or circle over a site to search for prey. Once they have chosen a target, they use a high-speed dive or ‘stoop’ to smack into the prey in mid-air. These dives can reach over 200 miles per hour (320 kilometres an hour), making them the fastest animal on Earth. Its hunting prowess means that it has been popular with falconers for thousands of years.

Population Changes

There have been some dramatic ups and downs in the peregrine’s fortunes in the UK over the last 75 years. In terms of range, they are the most widespread raptor globally. They are found in a variety of habitats that include open spaces and on all continents bar Antarctica.

However, in many places it was close to extinction in the middle years of the twentieth century. Harmful organochlorine pesticides (such as DDT) became concentrated in their tissues via their prey and led to the production of eggs that were infertile or with thinner shells than usual. Consequently, very few chicks hatched as shells were easily broken, and populations crashed. Persecution and egg theft were also factors; birds were hunted in large numbers in the nineteenth and twentieth centuries.

Following publicity about the harm chemicals posed by scientists including Rachel Carson, DDT use was tightly restricted. In the UK, organochlorines were banned in 1976. This, combined with conservation efforts, has led to the species’ recovery to a great extent in the UK. Birds are now spreading into more urban environments, with many towns and cities hosting a pair on the local church or cathedral. Tall man-made structures have turned out to be very similar to their natural clifftop nesting sites.

Church nesting peregrine
Churches are a popular nesting site

There are still causes for concern, however. Illegal persecution still occurs, with poisoned birds found with alarming regularity. Another threat is the increased use of gull netting on buildings. Used to deter gulls from nesting, birds of many species often get caught in the netting and if not freed, starve. A recent case involved one of this year’s fledgling peregrines from Leeds University. Fortunately, this bird was freed, but others may not be so lucky.

Peregrine Surveys

It is illegal to intentionally disturb peregrines or their young at the nest. As a result, a special licence is needed to carry out surveys if there is the potential for one to be nesting on a proposed development site. At Purple Plover, we are fully licenced to carry out species specific surveys for peregrines. These are essential for determining their presence, along with a site’s impact and whether mitigation measures are needed.