Longevity & Causes of Death

Raptors

Longevity & Causes of Death

Longevity

  1. Little is known about the longevity of diurnal birds of prey in the wild. One banded osprey lived 32 years, a golden eagle lived 25 years, and a honey buzzard lived 29 years (Welty, 1982).
  2. More complete records exist for birds in zoological parks. In general, small falcons and Accipiter hawks live about 15 years. Medium-sized buzzards and kites live 20 to 40 years, and large vultures and eagles have occasionally lived 40 to 55 years (Newton, 1979).

Aging Studies

  1. A bird's age is determined by marking a bird of known age (usually a nestling or fledgling, using a leg band) and recovering the bird when it dies. Recovering dead birds in the wild is a difficult task because carcasses are hard to locate and are quickly eaten. Most longevity studies take place on captive birds.

Predation

  1. Diurnal birds of prey are often victim to other, larger birds of prey, including owls.
    • Goshawks eat a variety of diurnal birds of prey including kestrels, buzzards, and kites.
    • Eagle owls (Bubo bubo) feed on buzzards, kestrels, kites, goshawks, and other owls.
    • In sparrowhawks (Accipiter nisus), the larger, mated female will prey on unmated males of the same species that try to court her.
  2. Eggs and young are vulnerable to predation by other birds, mammals, and reptiles.

Human Interaction

  1. Hunting.
    • Millions of diurnal birds of prey have been shot over the past 150 years. As a group, they have been persecuted for killing livestock, poultry, and game birds. In truth, only a few of the larger species occasionally feed on domestic animals. Some species, like the California condor, were shot for their feathers, or just for sport. Though diurnal birds of prey are currently protected in the United States, some illegal shooting still exists.
  2. Habitat destruction.
    • Deforestation and other habitat destruction is currently the most serious threat to diurnal birds of prey. Habitat loss not only affects birds in their breeding areas, but also in their wintering areas.
  3. Human structures and disturbance.
    • Accidental deaths occur when birds collide with humanmade structures such as buildings and power lines. Power line electrocution is frequent in larger birds, like vultures and eagles, whose wings can touch two wires at once.
    • Many carrion-eating birds are struck by cars while feeding on or near roads.
    • The practice of removing or burning dead livestock (to reduce the risk of disease) has inadvertently reduced the food supply of many scavengers, such as Old World vultures.
    • Diurnal birds of prey may abandon territories or nest sites if disturbed by human activity.
  4. Pollution.
    • Diurnal birds of prey, like all carnivores, are especially vulnerable to pesticides, insecticides, and other humanmade toxic chemicals.
      • As chemicals are passed up the food chain from plant to plant-eater, and from plant-eater to meat-eater, they become more and more concentrated in the tissues of each succeeding animal. This process is called bioaccumulation.
      • Organochlorines, such as DDT, PCB, and dieldrin are extremely harmful in concentrated amounts. A build up of organochlorines may cause death in adults and embryos, lead to chronic illness, or cause the thinning and premature breakage of egg shells. Though several organochlorines have been banned in the United States, including DDT in 1972, they're still used in other parts of the world.
    • Other forms of pollution, such as acid rain and oil spills, cause prey populations to decline, and in turn cause the decline of diurnal birds of prey populations.
    • Discarded trash, like used monofilament line, can entangle and harm individual diurnal birds of prey.
  5. Poisoning.
    • Diurnal birds of prey may be deliberately or accidentally poisoned. Though direct poisoning is illegal in the United States, it's still practiced in other areas of the world.
      • Accidental poisoning occurs when diurnal birds of prey eat rodents or seed-eating birds that have been poisoned by farmers for pest control.
      • Lead poisoning occurs when diurnal birds of prey eat carcasses or live prey shot with lead bullets. In the U.S., there's been a gradual elimination of lead from shotgun shells since the mid-1980s.
      • Diurnal birds of prey may also be killed by eating poison-laced carcasses set by ranchers for coyotes, wolves, jackals, or other animals considered pests. Some carcasses are set deliberately for diurnal birds of prey.
  6. Falconry.
    • Falconry is the sport of taking wild game by means of a trained bird of prey, usually a hawk or falcon. Falconry dates back to 2000 B.C. in China. As little as 10 years ago falconers were taking birds from the wild to train. Currently, most trained hawks and falcons are bred in captivity. A federal permit is required to keep birds of prey for falconry.

Disease & Parasitism

  1. Diurnal birds of prey are exposed to a variety of bacterial, viral, and fungal diseases, as well as internal and external parasites from the prey they eat. Though not usually fatal, infections may make a bird weak and vulnerable to other environmental factors.

Starvation

  1. Young nestlings and subadults are the most susceptible to starvation. Smaller nestlings are often unable to compete with their siblings for food. Subadults are inexperienced at catching their own food and, if the species is territorial, they must quickly establish a territory to hunt.