Species of interest: American crow
American crow (Corvus brachyrhynchos).Crow. Image courtesy of Wildlife Control Consultant, LLC.
Size: About a pound. Body is 17 to 21 inches long.
Signs of their presence:
The bird itself is the most obvious sign.
Sounds: Loud, raucous, throaty, “caws.”
Nest: Sticks, twigs, and coarse stems lined with shredded bark, feathers, grass, cloth, and string. Nests are 18 to 60 feet above the ground in tall trees, especially evergreens.
Lacking trees, crows may nest on the crossbars of telephone poles or on the ground.
Evidence of their feeding: Poor seeding of corn may be due to crow damage.
Crows will sometimes poke holes in garbage bags, insulation, or through roofs (especially on flat roofs covered with a rubbery membrane).
Opportunist. Crows are excellent hunters, pirates, and scavengers. They eat over 600 foods. A third of their diet consists of insects, frogs, salamanders, fish, snakes, bird eggs and young, small mammals, carrion (including roadkills), and garbage (in landfills); the rest is plants, mostly corn or waste grains in fields that have been harvested. They’ll also eat peanuts, sunflowers, pecans, various fruits, and sorghum. During the winter, they survive mostly on waste grain. From spring through summer, crows eat mostly worms, insects, and other invertebrates. One crow often acts as a sentinel while others feed.
Typical activity patterns:
Social style: Sociable, living in family groups with the young of previous years, who may help bring up the current brood. Crows gather and roost in flocks of ever-increasing size as the season progresses through winter.
Daily activity: Diurnal.
Migrates? Some do, some don’t.
Distribution: Most everywhere.
Habitat: Prefer open agricultural lands, old fields, meadows, with nearby orchards, woodlots, or hedgerows for nesting and cover. Crows are adapting to using parks and tree-lined streets in suburban and urban areas as large roosting areas and nest sites. They will fly up to 12 miles during the day to feeding sites, then return to the roost at night.
Territory and home range: Territorial during the nesting season.
- Pair bonding style: Monogamous. Crows have strong pair bonds that endure over the years, but they probably occasionally mate with others. Both sexes help build the nest and rear the young. Female incubates the eggs by herself, but the male will feed her and guard the nest when she leaves. (Other females may feed the incubating bird, too.)
- Breeding dates: From March to June. They lay their eggs in the end of March. One brood/year.
- Clutch size: 4 to 6. Young hatch in about 18 days.
- Fledging dates: About 35 days from hatching. The young leave the nest at 5 weeks to forage with parents.
- Amount of time young remain with parents beyond fledging date: Often one or more years.
Time of year: Any time of year.
What are they doing?
- Huge flocks—up to 25,000 crows or more in some areas–may roost together in the winter, especially in urban areas. With so many birds present, they can make an astounding racket and their weight may even break tree limbs. Noise, droppings, property damage, and possible public health hazards are common complaints.
- Eat farm crops, both vegetables and grains, especially corn. Crows will also damage home gardens, again, often for sweet corn. Ironically, crows may be attracted to the garden by the insect pests, but then stay to feast on the crop they protected.
- Eat bird eggs and young chicken and turkeys.
- Large flocks may spread diseases to other species: histoplasmosis to people, avian cholera to other birds (when the crows roost near wetlands), and gastroenteritis to swine (when they roost near farm buildings).
- They’ll sometimes poke holes in roofs, insulation, and garbage bags left outdoors.
- Rarely, groups of crows will attack newborn lambs, goats, calves, and pigs, but that’s more often the work of magpies or ravens.
- During the nesting season, crows may store food in trees, in the grass, or even in birdbaths or rain gutters—whatever’s handy to the nest. This collection of carcasses may not be appealing.
- Crows are very protective of their young before they fledge, and will attack predators that threaten the nest. Usually, this is a cat or dog, but if people are too close to the nest, the crows might mob them. This behavior stops as soon as the young can fly.
- Rarely, young crows will play with, and damage, windshield wiper blades. (Crows are very curious, and at that age, they’ll play with objects that older crows ignore.)
De-bunking myths about crows:
- Crows will attack people. Forget Hitchcock. Crows don’t attack people (unless you seem to be threatening their young).
- Crows are vectors for West Nile virus. Many crows have died from West Nile virus but they may play little role in spreading the disease. Mosquitoes are the main vector.
- A crow roost nearby will increase your risk of catching West Nile virus. Not true.
- Crows are impossible to distinguish from ravens. Crows are often mistaken for ravens (also a federally-protected bird). Ravens are larger and have a wedge-shaped tail; they’re mostly found in the Adirondacks and Catskills. The fish crow is more often found downstate in the lower Hudson Valley and Long Island.
Legal status in some states:
Federally-protected migratory bird (under the Migratory Bird Treaty Act). In many states, crows are a protected game species with an open season. An exception to the Migratory Bird Treaty Act allows the taking of crows without a federal permit when the birds are “found committing or about to commit depredations upon ornamental or shade trees, agricultural crops, livestock, or wildlife, or when concentrated in such numbers and manner to constitute a health hazard or other nuisance.” In these cases, you don’t need permits beyond your WCO license.
Sometimes, damage blamed on crows is caused by other species such as blackbirds, starlings, pheasants, grackles, or mice. Often, community cooperation is critical for effective solutions to nuisance problems caused by a large urban roost.
Make roosting sites less appealing:
- In a dense grove, thin trees. If a tree is a preferred roost site, trim out about a third of its branches, concentrating on the inside center of the crown. This will reduce the number of available perches and increase the birds’ exposure to weather. With less, and poorer shelter, fewer crows will congregate.
- A combination of frightening techniques (noises and visual deterrents) may convince the crows to leave a roost. As always, your chance of success increases if the techniques are used together and in an unpredictable fashion. Try noisemakers such as tape-recorded distress calls (crow squalling while under attack), clappers, shell crackers, propane cannons, shotguns, beating on tin sheets or barrels, and alarms. The Avian Dissuader™, a laser, has proved effective against crows (it’s a powerful tool so use it cautiously). Mylar tape, lights, bright objects, animated owl models (complete with a dummy crow attached to its talons), and dousing the birds with water from hoses or sprinklers that are mounted nearby may also work. Crows that are used to people and city noises may not respond.
- If young crows are damaging windshield wiper blades, try to chase them away, using the harassment techniques mentioned above. Or try changing the car’s appearance a bit to frighten them, by hanging a tassel on the antenna, for example. A car cover will protect the wipers, too.
Protect vulnerable crops:
- Are you sure the crows are causing more harm than good? They eat insect pests; mice; waste grain that could result in unwanted “volunteer” corn the next season; and carrion, which could attract other pests. Assess whether the damage justifies control, and remember to determine the real culprit.
- Exclusion is often impractical except for a valuable crop in a small area, where it may be cost-effective. Create a barrier with nylon or plastic netting.
- In a home garden, place paper cups or sacks over ripening sweet corn, once the silk has turned brown.
- Try frightening them, as described earlier.
Remove artificial food sources
(garbage, compost, bird seed, pet food):
- If anyone is feeding the crows, persuade them to stop.
- Enclose compost piles in a framed box using hardware cloth; in a sturdy container, such as a 55-gallon drum; or in a commercial composter.
- Feed pets indoors.
Trapping is probably impractical for large flocks. There may be some situations in which it makes sense, especially if there aren’t many crows in the area.
Australian crow trap. A large trap (8- to 10-feet square, 5 to 6 feet high) that uses both bait and a decoy to lure in the birds. This trap can be used with bait only, but be more patient, because that method is less effective. Bird eggs or carcasses are used as bait if there’s little risk of attracting carnivores such as dogs; otherwise, try whole corn, watermelon, or poultry feed. The decoy is a few live crows, who of course need food, water, and shelter. See Prevention and Control of Wildlife Damage for details.
Preferred killing methods:
- CO2 chamber
- Cervical dislocation
- Shooting (air rifle, shotgun, or .22-caliber rifle)
- Stunning and chest compression
Control strategies that don’t work particularly well, or aren’t legal in some states:
- Ultrasonic devices don’t work. Birds can’t hear them.
- There have been mixed results with grid-wire systems.