Damage and Damage Identification
The most troublesome raptors are the larger, more aggressive species, such as the goshawk, red-tailed hawk, and great horned owl. The majority of depredation problems occur with free-ranging farmyard poultry and game farm fowl. Chickens, turkeys, ducks, geese, and pigeons are vulnerable because they are very conspicuous, unwary, and usually concentrated in areas that lack escape cover. Confined fowl that are chased by raptors will often pile up in a corner, resulting in the suffocation of some birds. Reproduction may also be impaired in some fowl if harassment persists.
For years, game farms have dealt with raptor depredation problems. Large concentrations of game farm animals are strong attractants to predators. Operators should consider the prevention of predation as part of their cost of operation. Other depredation problems include the loss of rabbits at beagle clubs, the loss of homing and racing pigeons, and occasionally the loss of farm or household pets. Cooper’s and sharp-shinned hawks occasionally prey on songbirds that are attracted to feeding stations. This should be viewed as a natural event, however, and control of the raptors is not advisable.
There are occasions when raptors cause human safety and health hazards. For example, concentrations of raptors at airports increase the risk of bird-aircraft collisions and loss of human life. The vast majority of aircraft strikes involve gulls, starlings, and blackbirds, but a few raptor strikes have been documented. It is interesting to note that falconers with trained hawks have been used to clear airport runways of other birds so that airplanes can land. Although raptors are usually secretive and choose to avoid human contact, they occasionally nest or roost in close association with humans. At such times, noise, property damage, and aggressive behavior at nest sites can cause problems.
Poultry and other livestock are vulnerable to a wide range of predators. Frequent sightings of hawks and owls near the depredation site may be a clue to the predator involved, but these sightings could be misleading. When a partially eaten carcass is found, it is often difficult to determine the cause of death. In all cases, the remains must be carefully examined. Raptors usually kill only one bird per day. Raptor kills usually have bloody puncture wounds in the back and breast from the bird’s talons. Owls often remove and eat the head and sometimes the neck of their prey. In contrast, mammalian predators such as skunks or raccoons often kill several animals during a night. They will usually tear skin and muscle tissue from the carcass and cut through the feathers of birds with their sharp teeth.
Hawks pluck birds, leaving piles of feathers on the ground. Beak marks can sometimes be seen on the shafts of these plucked feathers. Owls also pluck their prey, but at times they will swallow small animals whole. Many raptors (especially red-tailed hawks and other buteos) feed on carrion. The plucked feathers can often determine whether a raptor actually killed an animal or was simply “caught in the act” of feeding on a bird that had died of other causes. If the feathers have small amounts of tissue clinging to their bases, they were plucked from a cold bird that died of another cause. If the base of a feather is smooth and clean, the bird was plucked shortly after it was killed.
Raptors often defecate at a kill site. Accipiters such as the goshawk leave a splash or streak of whitewash that radiates out from the feather pile, whereas owls leave small heaps of chalky whitewash on the ground.
Hawks and owls regurgitate pellets that are accumulations of bones, teeth, hair, and other undigested materials. These are not usually found at the kill site, but instead accumulate along with whitewash beneath a nearby perch or nest site. Fresh pellets, especially of owls, are covered with a moist iridescent sheen. They can be carefully teased apart and examined to learn what the hawk or owl had been eating. Owls gulp their food and swallow many bones along with the flesh. These bones are only slightly digested and persist in the pellets. A pellet that contains large bones, such as those from the leg of a rabbit, is undoubtedly from a great horned owl. Hawks feed more daintily and have stronger digestive juices than owls. Thus, hawk pellets contain fewer bones.
All hawks and owls are federally protected under the Migratory Bird Treaty Act (16 USC, 703-711). These laws strictly prohibit the capture, killing, or possession of hawks or owls without special permit. No permits are required to scare depredating migratory birds except for endangered or threatened species (see Table 1), including bald and golden eagles.
In addition, most states have regulations regarding hawks and owls. Some species may be common in one state but may be on a state endangered species list in another. Consult your local USDA-APHIS-Animal Damage Control, US Fish and Wildlife Service (USFWS), and/or state wildlife department representatives for permit requirements and information.
|Name||Status||Where Endangered||Where Threatened|
|California condor(Gymnogyps californianus)||Endangered||US (California and Oregon), Mexico (Baja California).|
|Bald eagle (Haliaeetus leucocephalus)||Endangered and Threatened||US (Conterminous states except Michigan, Minnesota, Oregon, Washington, and Wisconsin)||US (Michigan, Minnesota, Oregon, Washington, and Wisconsin)|
|American peregrine falcon (Falco peregrinis anatum)||Endangered||Nests from central Alaska across north central Canada to central Mexico. Winters south to South America.|
|American peregrine falcon (Falco peregrinis tundrius)||Threatened||Nests from northern Alaska to Greenland. Winters south to Central and South America.|
|Peregrine falcon (Falco peregrinis)||Endangered||Wherever found in wild in the conterminous 48 states.|
|Hawaiian (lo) hawk (Buteo solitarius)||Endangered||US (Hawaii)|
|Name: Everglade (snail kite) kite (Rostrhamus sociabilis plumbeus)||Endangered||US (Florida)|
|Name: Palau owl (Pyroglaux [=Otus] podargina)||Endangered||West Pacific Ocean: US (Palau Islands)|
Economics of Damage and Control
In 1985, we conducted a national survey of US Fish and Wildlife Service and Cooperative Extension personnel. Nearly all noted that the economic damage caused by raptors is minimal on a national scale, but can be locally severe if depredation occurs on fowl or livestock that are relatively valuable and vulnerable.
Cost estimates of damage ranged from $10 to $5,000 per report and from $70 to $94,000 per year. The severity of raptor problems is influenced by several factors, including prey and carrion abundance, weather, time of year, husbandry methods, vegetative cover, and topography as well as density and local distribution of raptors.
Summary of Damage Prevention and Control Methods
Livestock confinement is the most effective control method, but it must be practical and economical.
Confine free-roaming fowl in enclosures covered with netting or woven wire.
Condition poultry and fowl to move into coops or houses by feeding and watering them indoors at dusk.
House them at night to protect them from owls.
Eliminate perch sites near areas of potential damage by removing large, isolated trees and snags.
Install utility lines underground and remove telephone poles near poultry-rearing sites.
Cap poles with sheet metal cones, Nixalite®, Cat Claws®, or inverted spikes.
Use scarecrows and pyrotechnics.
Erect electric pole shockers when hawks or owls are observed around areas of potential damage.
None are registered.
None are registered.
Trapping and Relocating
State and federal permits are required to trap and relocate hawks and owls. If possible, experienced bird banders or trappers should do the trapping.
Landowners, however, can safely trap hawks and owls if they follow instructions and are careful when handling the birds.
State and federal permits are required to shoot hawks and owls. They may be issued only when there is a serious public health or depredation problem and when nonlethal control methods fail or are impractical.