Emerging Conservation Issues
As top predators, raptors often exist at low densities and exhibit low reproductive rates. Raptors typically require large acreages in which to forage, they need healthy prey populations for their often specialized diets, and they have a propensity to concentrate environmental toxins. For these reasons, raptors are vulnerable and sensitive to change in the environment and thus, can serve as indicators of broader biodiversity and environmental health. Around the world there are numerous examples of raptors affected at population levels by environmental toxins and land use change.
• Historically, Peregrine Falcons, Bald Eagles and other raptors declined in North America and Europe with the agricultural use of DDT. Populations subsequently recovered after DDT was banned in the early 1970s, but it took about 30 years for populations of some species to recover sufficiently for them to be removed from the U.S. endangered species list.
• Today in the United States, critically endangered California Condors can not survive in the wild as a result of lead poisoning from spent ammunition in the scavenged remains of hunter harvested game.
• Bald Eagles and Golden Eagles also die from this source of lead exposure, though population level impacts are difficult to discern.
• In South Asia, three species of Gyps vultures have been decimated by residues of diclofenac, a pharmaceutical used to treat livestock that subsequently become vulture food.
• In East Africa, avian scavengers are poisoned by pastoralists’ attempts to control predators of livestock using chemicals such as Furadan, a very low cost carbamate pesticide.
• In the U.S., American Kestrel populations have declined at regional levels, but the cause(s) remain to be determined and may prove to be more than one cause over large spatial and/or temporal scales.
• Collision of soaring raptors with wind energy turbines is of current concern; these turbines are often are sited in areas of constant wind favored by migrating raptors for the same reasons.
• Electrocution on power lines remains a threat to raptors worldwide despite advances in power pole design and clear benefits to power companies to minimize electrocution.
• Shooting, or other forms of direct human persecution, is still a significant conservation issue worldwide, despite decades of public awareness and outreach. Harpy Eagles, for example, are depleted from their rain forest habitat in Central America by shooting even before the forest is cleared.
• Loss of habitat is a problem for many endemic island species where the species’ range is limited by the island’s size and available habitat remaining on it. For example, the Ridgway’s Hawk,
a species endemic to the Caribbean island of Hispaniola is now found only in a small patch of forest in Los Haitises National Park. Such limited range species are vulnerable to natural stochastic events like hurricane, fire, or disease.
• Another example is the Philippine Eagle; in this species’ native land the lowland forest has been virtually completely cleared, and only small remnants on the steeper mountain slopes remain protected from the axe. Battles between government forces and insurgents make conservation of this species even more difficult to confront than usual.