The Canadian Peregrine Foundation

Peregrine Biology:
Conservation Issues


Population sizes --- Decline --- Recovery --- Peregrines and humans

 

Population Sizes - Historically and Presently:
Historically, Peregrines were renowned for having remarkably stable populations. Records are best documented for Great Britain, where the breeding population remained steady around 800 pairs from the time of Queen Elizabeth I to the Second World War nearly 400 years later. Even more amazingly, some particular nest sites were almost continuously occupied throughout this period.

Peregrine populations around the world declined severely after the Second World War.  Prior to the 1940s, there were roughly 7000 Peregrines in North America, the majority of which were in Alaska or the Canadian Arctic. In Europe, there were at least 8000 additional Peregrines, mostly in Fennoscandia and Spain, with smaller numbers in France, Britain, and Germany. At their lowest point in the 1970s, populations dropped to several hundred in North America and under 1000 in Europe. The status of the Peregrine in other parts of the world has not been as well documented.

Populations everywhere have started to recover. By the late 1980s, there were again as many as 1200 pairs in North America, and in Europe there were over 4000. While there are a few locations where populations have returned to or exceeded historical levels (e.g. Switzerland, Britain), in most areas the Peregrine still has a long way to go to achieve a full recovery.

In Canada, all three subspecies of the Peregrine were added to the Endangered Species list in 1978: the Anatum Peregrine as endangered, the Tundra Peregrine as threatened, and the Peale's Peregrine as rare. Since then, the status of the Tundra Peregrine has been downgraded to vulnerable (in 1992), and the Peale's Peregrine was reassessed as vulnerable (in 1990). In the United States, the Anatum and Tundra Peregrines were designated as endangered in 1970. The Tundra subspecies was reclassified as threatened in 1984, and was removed from the Endangered Species list entirely in October 1994, following a review which indicated a healthy and growing population in the Arctic. The Anatum was removed from the US Endangered Species list in 1999.

 

Peregrine Decline:
In the early 1960s, researchers in both Britain and North America conducted independent surveys of historical Peregrine nesting sites. Both found that there had been a catastrophic decline in breeding numbers. In the eastern United States, where there had been over 300 nests as recently as the middle of the twentieth century, not a single active nest could be found in 1963. In fact, it was soon discovered that Peregrines had disappeared entirely from the eastern third of North America, south of the boreal forest and east of the Mississippi River. Throughout Europe similar discoveries were made, and some populations, such as a rare tree-nesting race in Germany, became extinct. For several years, scientists were unsure what had caused the Peregrine populations to collapse so rapidly.

Over time, it became more and more evident that the organochlorine known as DDT (dichlorodiphenyltrichloroethane) was at least partly responsible for the decline. DDT was released for use as an insecticide in 1945, and quickly became one of the most heavily applied insecticides around the world. It was popular in large part because it is a broad spectrum pesticide, and thus is effective against a wide variety of insects, ranging from those which plague agricultural crops to insects such as mosquitoes which transmit malaria and other diseases to humans. Its other main attraction was that it was persistent (i.e. chemically stable and long-lasting), and could therefore be applied a single time and be effective for months to come. While this was initially seen as a tremendous benefit, it proved to be a great liability to the Peregrine.

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 leaves and seeds for a long time. Herbivores which ate these then ingested the DDT. Because DDT is fat soluble but not water soluble (like its breakdown product, DDE), it accumulated in their tissues and could not be excreted. When Peregrines caught and ate birds contaminated with DDT, it was transferred to their tissues. Peregrines suffered more than some other animals, due to bioaccumulation. Seed eaters ingested relatively small quantities of DDT, and although it collected in their tissues, it rarely reached toxic levels. However, when predators ate these animals, the DDT was passed along to them, and with each contaminated individual they ate, the predators accumulated more DDT.

As levels of DDT in Peregrines and other predators became extremely elevated, some died from poisoning. More often they survived, but were unable to reproduce. It was found that DDT disrupted the reproductive system of female birds. In some cases it prevented them from laying eggs at all, while in others eggs were produced, but had extremely thin and weak shells, because DDT interfered with their ability to allocate calcium to egg production. Eggs with such thin shells cracked during incubation. For many years, hardly any Peregrines were able to produce any young.

North American researchers believe that DDT was primarily responsible for the decline of the Peregrine. In Europe, many scientists contend that while DDT played a significant role, other chemicals were also at fault. Most notably, two closely related organochlorines called aldrin and dieldrin are believed to have killed many adult Peregrines. These two insecticides were introduced in Britain in 1956, and were widely used to coat seeds to protect them from insects. Almost immediately, naturalists noticed that seed-eating songbirds, as well as their predators, were dying in large numbers. Within less than a decade, the use of both aldrin and dieldrin was severely restricted in Britain, and many species began to recover, including the Peregrine.

 

Recovery:
In the early 1970s, the future of the Peregrine looked bleak. Even though DDT was banned in Canada, the United States, and most of western Europe early in the decade, residues lingered in the environment at high levels, and the population of Peregrines had fallen to precipitously low levels. Furthermore, many of the surviving birds were so highly contaminated with DDT that they could not reproduce.

Later in the decade, signs of hope began to be seen. 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, including over 600 in Ontario alone. Smaller numbers have been bred and released across Europe. While many releases appear to have failed, some individuals did survive and established territories, and populations in many areas are now slowly increasing each year. The Peregrines now living in eastern North America are all either birds which have been released, or descendants of captive bred birds.

 

Peregrines and Humans:
Peregrines and humans have a long history together. For over 3000 years, it has been a favourite species of falconers, and historical records show that the Peregrine has long been held in high esteem in many cultures around the world. Unfortunately, a few hundred years ago attitudes changed for the worse, and the Peregrine along with most other birds of prey became widely persecuted. For many years they were hunted with reckless abandon. Later, through the use of harmful pesticides, humans unwittingly dealt an even more severe blow to Peregrine populations. Only in the past couple of decades have humans again started to help rather than hurt Peregrines.

How humans have hurt peregrines:
Hunting has been a major cause of population decline for most raptors. Beginning in the 1700s, great efforts were made throughout Europe and North America to wipe out all birds of prey because they were perceived to be a threat to livestock and animals such as hares and grouse which were favoured by hunters. Even as late as the 1960s, as many as 120 000 birds of prey were being killed in the Soviet Union each year. While attitudes (and laws) have changed considerably in the past few decades, there are incredibly still many people who believe that birds of prey are a threat to their animals or even to their children. Despite extensive proof that such incidents are extremely rare, many raptors continue to be shot every year because this popular myth persists.

There is also a great demand for a wide variety of raptors in the taxidermy trade, especially in Europe and Asia. Some species, especially Peregrines and other falcons, are even more highly prized alive. In the Middle East, where falconry is the sport of the elite, single birds have been bought for as much as $100 000 each. To satisfy the demand, poachers have been known to steal eggs and chicks from nests.

Hunting and poaching have been taking place for hundreds of years, yet the Peregrine did not decline until earlier this century. The added stress of organochlorine poisoning in the form of DDT, aldrin, and dieldrin, appears to have been too much for the Peregrine to withstand. With reproduction impaired by these chemicals, Peregrines had no way to compensate for other population losses.

Studies within the past decade have in fact shown that many Peregrines breeding in North America still show alarmingly high levels of DDT. Many eggshells are still only just barely strong enough to withstand incubation. Partly this is due to DDT residues which have remained in the environment for decades. Mostly, however, it is because these Peregrines spend the winter in areas of Central and South America where DDT is still applied in large quantities. The Peregrines accumulate it over several months, and by the time they return to their breeding grounds, they are sufficiently poisoned that reproduction can be inhibited. Even non-migratory Peregrines can suffer DDT poisoning if they prey on migrant birds which have fed on contaminated grains while wintering in countries where DDT is still applied.

How humans have helped peregrines:
The fate of the Peregrine depends on human assistance. Without the efforts made in recent decades to reduce the use of DDT and other pesticides, the Peregrine Falcon might already be extinct. However, the Peregrine is not safe yet. DDT and other hazardous pesticides continue to be used in some Central and South American countries, and North American Peregrines are being both directly and indirectly poisoned as a result.

Agricultural farming can be done with little or no pesticide use, and still be both highly productive and highly profitable. Integrated pest management, where pesticides are used minimally and only as a last resort, has been shown to be effective in a variety of climates around the world. However, it will take time to change the mind set of farmers worldwide. Around 1990, it was estimated that 21.5 billion kilograms (47 billion pounds) of pesticides were being applied around the world on an annual basis.

Efforts to help the Peregrine recover can be made in many areas. Obviously eliminating the use of harmful pesticides and preventing the killing and illegal trade of Peregrines would go a long way toward helping populations grow. Stricter enforcement of existing laws would be beneficial, but long term success will be achieved only if people are educated about the value of the Peregrine and other endangered species, and come to understand the need to protect them.

In Canada, the protection of the Peregrine falls under provincial jurisdiction. In Ontario and New Brunswick it is protected by the Endangered Species Act, which prohibits all shooting, collecting, and harassment of Peregrines, as well as destruction of their habitat. In the rest of Canada, only collection and harassment are illegal. The import and export of Peregrines and their eggs is also banned under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Many tangible projects have been undertaken to help the Peregrine. Captive breeding and subsequent releases have proven to be instrumental to the recolonization of eastern North America. Providing nest boxes to Peregrines establishing territories in urban areas has also proved to help increase their success rate.

Because the Peregrine still faces so many threats, it is vital that as much as possible be done to help each individual survive. At urban nest sites, this means keeping the nest under surveillance and operating a dawn-to-dusk Fledgling Watch during the two to three week period when the chicks are learning to fly. If they come down to the ground on one of their early flights, either as a result of having fledged prematurely and not having enough strength to stay aloft, or due to hitting a building and falling dazed to the ground, they can be rescued quickly and brought to safety. Without human intervention these birds would likely fall victim to predators or other urban hazards. Considering that the vast majority of urban Peregrine chicks do end up down on the ground soon after they learn to fly, the Fledgling Watches are critical to the success of these nests.

How Peregrines have helped humans:
For much of human history, the Peregrine has been a highly respected and valued species. They were one of the first birds used by falconers, and when falconry was at its peak of popularity in Europe during the Middle Ages, the Peregrine was classified as a "noble hawk," and was reserved for the upper class. While the rich and the royal used the birds for sport, the peasants at the same time relied on the Peregrine and other falcons to hunt food for their own families, because it was the only way they could acquire meat of any kind.

More recently, the Peregrine has played an even more important role, as a sensitive and accurate barometer of environmental health. The decline of the Peregrine Falcon in the 1950s and 1960s led scientists to investigate the nature of DDT, and it was only then that they discovered the sinister side of this chemical. The decline of the Peregrine triggered an investigation into the effects of DDT and other related chemicals, which has had significant benefits for birds and humans alike. While there is no documentation of humans suffering from DDT poisoning, it is conceivable that over time levels would have accumulated to hazardous concentrations since, like the Peregrine, humans are at the top of the food pyramid. Moreover, the Peregrine's reaction to DDT has made us more aware of the essential need to do careful and thorough studies of all chemicals before releasing them for use, and this can only be beneficial for all of earth's inhabitants.

 

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