Food for Birds of Prey

Food for Birds of Prey
What Do Birds of Prey Eat?

By Melissa Mayntz, About.com Guide

Birds of prey are not only defined by their physical characteristics, but also by their carnivorous diets. While it is widely assumed that the primary prey for raptors is small mammals, these birds actually have a varied diet that can include many different types of game.

What Birds of Prey Eat

Different types of birds of prey eat a wide range of different animals. In general, the larger the bird the larger the prey, but many medium and large raptors will also choose easier, smaller meals. The most common prey of raptors includes:

*Large Insects: Grasshoppers, praying mantises and other large insects are the preferred prey of small raptors such as American kestrels, merlins and Mississippi kites. Raptors that spend a large amount of time on the ground, such as burrowing owls, also eat a lot of insects.

*Fish: Birds of prey that live along coastlines or near large bodies of water often hunt fish, in some cases poaching it from other predators such as bears, raccoons and mountain lions. Fish is the majority of the diet for bald eagles and osprey, and the snowy owl will also occasionally eat fish.

*Small Mammals: Small mammals such as mice, voles, shrews and gophers are the most popular prey for medium and large raptors. Red-tailed hawks, northern harriers, Cooper’s hawks, barn owls, merlins and many other species hunt small mammals, either by perching and scanning fields or by soaring to spot prey.

*Small Birds: Many small birds, including finches, sparrows and songbirds are prey for larger birds. Depending on the raptor species, they may surprise the smaller birds on the ground or catch them in mid-flight, either through diving or after an acrobatic aerial chase.

*Large Birds: Larger birds such as pigeons, doves, ducks and grouse often become prey for larger raptors. Fierce predators such as the northern goshawk and the swift diving peregrine falcon feed frequently on larger birds.

*Medium Mammals: Medium-sized mammals such as rabbits, raccoons and large squirrels are regular parts of the diet of large birds of prey. Red-tailed hawks, ferruginous hawks, northern goshawks and golden eagles hunt these bigger mammals.

*Carrion: Dead animals and rotting carcasses are the primary diet of scavenging raptors such as the turkey vulture and the California condor. Other large raptors, including golden and bald eagles, will also choose an easy meal like carrion if it is available.

*Reptiles: Snakes and lizards are popular prey for desert dwelling raptors such as the crested caracara. The barred owl is also known to feed frequently on reptiles.

*Amphibians: Smaller birds of prey and those that prefer habitats near water often feed on amphibians such as frogs and salamanders. Red-shouldered hawks and American kestrels often include amphibians in their diet.
Birds of Prey in the Backyard

While raptors are not common backyard birds, smaller species such as the sharp-shinned hawk, American kestrel and Cooper’s hawk may occasionally show up in suburban and urban areas. While they will mainly hunt small birds, mammals and insects, they have also been known to take large chunks of suet if available.

Meat and poultry scraps are also taken by raptors of all sizes, though adding them to a backyard bird feeding station is unlikely to attract birds of prey. It is not recommended to offer meat in order to tempt raptors, since meat scraps can also attract other animals and predators that can be dangerous.

Raptors Eating Backyard Birds

Many backyard birders dislike birds of prey hunting and feeding on their backyard birds, and conscientious birders may consider attracting backyard birds an ethical dilemma when it results in a raptor buffet. It is important to remember, however, that having a hawk visit a backyard demonstrates the great bird diversity of the area and the suitability of the backyard habitat, since raptors will not hunt where prey is scarce.

When raptors do take backyard birds, they are usually capturing the oldest and weakest birds. By culling these less than prime specimens, they actually help improve the strength of the backyard flock and will help the other birds survive. Nevertheless, backyard birders who prefer to protect their songbirds can do so by offering suitable shelter for the birds to hide from passing raptors. If a hawk returns regularly to the same spot to feed, removing all birdfeeders for a week or two will disperse the backyard flock and encourage the raptor to find a more suitable hunting ground.

From insects and fish to mammals, lizards and frogs, birds of prey have a highly varied diet. Even when they prey on backyard birds, they are still a fascinating and valuable part of the ecological food chain.

DIET & EATING HABITS

FOOD PREFERENCES & RESOURCES
1. All diurnal birds of prey eat some type of animal flesh, including reptiles, insects, fish, birds, mammals, molluscs, and carrion.


2. Groups of birds favor certain foods.

•Most Old and New World vultures prefer to eat carrion. Many diurnal birds of prey include carrion in their diet; but in vultures, carrion tends to be the main food source.

•Larger falcons and Accipiter hawks eat mostly birds.
° Peregrine falcons feed on doves, pigeons, grouse, shorebirds, and jays.

° Sharp-shinned hawks eat sparrows, robins, and warblers.
•Buteo hawks tend to feed on mammals, such as mice, voles, ground squirrels, rats, rabbits, and gophers.

3. Some species have specialized diets.

•Ospreys feed almost exclusively on fish.

•Palmnut vultures (Gypohierax angolensis) feed mainly on the fruit and husks of palms, though they occasionally eat fishes or insects.
•Honey buzzards (Pernis apivorus) prefer wasps and their larvae or pupae.
•Bat hawks (Macheiramphus alcinus) eat bats.
•Snail kites dine on apple snails.
•Lesser kestrels (Falco naumanni) feed on grasshoppers and locusts.

4. In general, diurnal birds of prey feed on game that average 12% to 50% of their own body weight. Occasionally, larger species will catch prey their own weight or larger (Johnsgard, 1990).

•A harpy eagle of South America was recorded carrying a sloth weighing 5.9 kg (13 lb.) (Martin, 1987).

•A bald eagle was seen carrying a mule deer fawn weighing 6.8 kg (15 lb.) (Martin, 1987).

FOOD INTAKE
1.The amount of food a diurnal bird of prey eats depends largely on the species, size, and sex of the bird.

•Smaller birds have a larger surface area to body volume ratio than larger birds, causing them to lose body heat more rapidly. To compensate, smaller birds usually eat proportionately more food than larger birds to maintain their metabolism and body temperature.

° A nonbreeding black-shouldered kite (Elanus caeruleus) weighing on average 0.25 kg (.55 lb.) eats about 20% of its body weight per day (Pickford and Tarboton, 1989).

° On the other hand, a cape vulture weighing on average 9 kg (20 lb.) eats about 6% of its body weight per day (Pickford and Tarboton, 1989).
•In many species the female is larger than the male and therefore captures and consumes larger prey. For instance, the average female sharp-shinned hawk captures prey weighing up to 300 g (0.7 lb.), while the average male captures prey weighing up to 100 g (0.2 lb.). Scientists believe the size difference between mated pairs reduces competition for food during the breeding season (Johnsgard, 1990).

2.Food consumption is also influenced by season. Food intake increases in cold weather, before migration, and before egg laying (in females).

METHODS OF COLLECTING & EATING FOOD
1.The majority of diurnal birds of prey hunt independently, and capture and kill game with their talons. Falcons use both their talons and beak to subdue prey.


2.Group hunting has been observed in wintering Harris' hawks (Parabuteo unicinctus), where individuals cooperate to flush and ambush prey.


3.Birds that feed on invertebrates tend to have higher hunting success rates than those that feed on vertebrates. In one study, attacks on invertebrates by American kestrels had a 85% success rate. Attacks on vertebrates had a 23% success rate (Cade, 1982).


4.The capture and killing of vertebrate prey is a highly developed skill that varies from species to species.

•Ospreys capture fish at shallow depths after a dive of 5 to 70 m (16-230 ft.) (Johnsgard, 1990). Dives are usually initiated from a flapping, gliding, or hovering flight. At the final stage of the dive, the feet are thrust forward and the wings are held directly back. The birds may disappear into a spray of water before emerging with a fish (typically carried head forward).

•When attacking from a stoop, the peregrine falcon will strike its prey (a bird) with a hind talon, knocking it to the ground. If the prey is not sufficiently stunned, the falcon will attack again. Peregrines are the world's fastest moving bird, reaching speeds up to 180 kph (112 mph) when stooping (Martin, 1987).

5.In addition to capturing their own prey, many birds, including peregrine falcons and bald eagles, steal prey from other birds.


6.Once the prey is subdued, the bird usually "mantles", spreading its wings out and over the prey. Mantling shields the prey from theft by other birds. Many bird-eating species pluck the larger feathers before tearing and consuming the prey.

7.Some Old World vultures, whose main diet is carrion, have unique ways to obtain food.

•Many African species dine on the same carcass, but they arrive and feed at different times. The powerful whiteheaded vultures usually arrive first, cautiously approaching the carcass before tearing open the tough hide. They're soon joined by whitebacked vultures (Gyps africanus) that assist in quickly exposing the carcass' entrails. Ruppell's griffon vultures (Gyps rueppellii) may arrive next, thrusting their long necks into the open carcass to obtain pieces of soft flesh. Lappetfaced vultures typically feed last, eating the remaining skin, tendons, and ligaments.

•Bearded vultures, who feed on bone marrow, break open large carcass bones by lifting them into the air and dropping them onto rocks.
•Egyptian vultures (Neophron percnopterus) drop rocks onto ostrich eggs to break them open for eating.

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http://elibrary.unm.edu/sora/jrr/v010n02/p00045-p00049.pdf

NUTRITIVE VALUES OF WHOLE-ANIMAL DIETS
FOR CAPTIVE BIRDS OF PREY
by D. M. Bird / S. K. Ho