Swainson's Hawks - Conservation Issues

Completing the long, arduous journey between the pampas of South America and the breeding grounds in the North is an increasingly difficult challenge for Swainson's Hawks, as well as for other migrating birds. As land development increases along the migration routes, suitable feeding and resting habitat is severely decreased. This problem is most acute in continental "bottlenecks", such as the area between Veracruz, Mexico and the Isthmus of Panama where the land corridor narrows to a mere 45 miles wide. In these areas, the migrating hawks are collected and funneled through in huge masses, making these corridors critical points in the migration route.

Unfortunately, this particular region has undergone drastic changes in landscape. Because of an increased demand for food production and export crops, much of the native dry tropical forest has been cut and converted into pasture for livestock grazing and sugarcane fields. This loss of resting habitat forces the hawks to roost in smaller patches of forest and on the ground,leaving them much more vulnerable. Preserving this crucial habitat is essential for the continued survival of migrating raptors.

Although raptors are now legally protected in many countries, there is still a serious lack of education about the value of raptors in the ecological balance. Illegal shooting still occurs on a large scale in some areas. Many hawks are shot at night while roosting, using lanterns and guns. Some birds are used as food and for rendering the fat for traditional medicines. In many other areas of Latin America, many hawks are shot for sport. Swainson's tend to be easy targets since they travel in such large numbers and often roost on the ground if insufficient trees are available. One step to counteract the loss of migratory corridor habitat and to seek increased protection for raptors, has been the formation of Hawks Aloft Worldwide, founded by the internationally respected Hawk Mountain Sanctuary. This institute is providing education and training about land conservation to organizations around the world, as well as creating a global atlas of migratory raptor watch sites.

In addition to loss of habitat, pesticide poisoning is becoming an increasingly serious problem for migrating Swainson's Hawks. Many toxic pesticides which have been banned in the United States, are applied freely throughout much of Latin America. In fact, United States chemical companies annually ship huge amounts of hazardous pesticides that are banned or severely restricted in the U.S., with most of them going to developing countries.

There are numerous categories of chemical compounds with varying degrees of toxicity which affect raptors and other wildlife. Organochlorines (in particular, DDT) are especially dangerous to wildlife for several reasons. First, since they are very stable chemically, they can remain in the ecosystem for years. Second, these compounds accumulate in the fats of the animals that consume them, so are readily passed from prey to predator. And third, these pesticides can be widely dispersed by wind, water, and in the bodies of migratory animals. As a result, birds who live far away from agricultural areas may still have high levels of pesticides in their bodies. As a pesticide is ingested by a prey species, which is then consumed by a predator, the chemical is increasingly concentrated as it moves up the food chain. The pesticide may be several million times more concentrated in the tissues of a raptor than when it was originally applied to a crop. DDT is especially notorious for blocking the deposition of calcium in eggshells, resulting in drastically weakened shells that crack or dehydrate before hatching. Fortunately, DDT has been banned in North America and Europe. However, it is still manufactured and exported for use in other parts of the world, so may be transported by migratory birds, leading to further contamination.

Many other pesticides, fungicides, and herbicides are also used in agriculture. Because of concern for the environment, most of them are designed to break down quickly. This is an improvement, since they don't concentrate in the food chain as highly as chemicals such as DDT. However, these chemicals are still highly toxic to raptors. The birds can absorb them in sprayed areas directly through their skin, during preening, or by consuming contaminated prey.

Some believe the Swainson's Hawk population has sharply declined during the last fifty years. Loss of habitat continues to be a concern, but pesticides have recently been identified as a heavy contributor to the population losses. Much attention is now being focused on the wintering home of the hawks, the pampas of Argentina. These grasslands have been traditionally used for hay production and pasturing cattle. Since they also have a high density of grasshoppers, the pampas are a perfect winter habitat for Swainson's. However, in recent years, the land usage has shifted towards the commercial production of alfalfa, sunflowers, soybeans, and corn. The production of these crops involves the heavy application of pesticides to control grasshopper infestations. As a result, thousands of Swainson's Hawks are dying from pesticide poisoning.

The pesticide identified as the primary culprit was the organophosphate, monocrotophos, which is banned in the United States and Canada. Monocrotophos is regarded as one of the most highly toxic pesticides to birds. The hawks ingest it by eating contaminated grasshoppers or by direct contact with the pesticide. They often follow spraying tractors, foraging for the grasshoppers that are stirred up. They then ingest the pesticides as they preen their feathers.

The crisis was uncovered when an alarming decrease in the Swainson's Hawk population was investigated. In 1994, the Klamath National Forest initiated a study of their annual migration and wintering habits through the use of satellite telemetry tracking of individual birds. In January, 1995, Brian Woodbridge of the U.S. Forest Service, traveled to Las Pampas, Argentina, where he discovered thousands of birds that had been killed from monocrotophos poisoning. The U.S. Forest Service - Pacific Southwest Region Web Site includes a fascinating look at their involvement with Swainson's Hawk issues. This triggered an international collaborative effort between conservationists, industry, and government officials from the United States, Canada, and Argentina.

This situation illustrates the interconnections between continents and habitats. Since a serious ecological crisis such as this knows no geographical or political boundaries, governments and people must work together to take whatever measures are necessary to ensure the preservation of species such as the Swainson's hawk.