Appendix C: What to do with a complaint about protected wildlife species
American crow (Corvus brachyrhynchos)
Size:
About a pound. Body is 17–21" 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 18–60 ft. 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 seedings 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).
Diet:
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 seasons progress through
winter.
Daily activity: Diurnal.
Hibernator? No.
Migrates? Some do, some don't.
Where found:
Distribution in NY and the Northeast: 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.
Breeding habits:
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–June. They lay
their eggs in the end of March. One brood/year.
Clutch size: 4–6. 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.
Common nuisance situations:
Time of year: Any time of year.
What are they doing?
- Huge flocks—up to 25,000 crows 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:
- Forget Hitchcock. Crows don't attack people (unless you seem to be threatening
their young).
- Many crows have died from West Nile virus but they may not play much of
a role in spreading the disease. Mosquitoes are the main vector.
- A crow roost nearby does not increase your risk of catching West Nile virus.
- 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 found downstate in the lower Hudson Valley
and Long Island.
Legal status in New York:
Federally protected migratory bird (under the Migratory Bird Treaty Act). In
New York, 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
NWCO license.
Best practices
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 but for a valuable crop, especially one in
a small area, 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 strategies:
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.
Live traps:
- Australian crow trap. A large trap (8–10 ft. square, 5–6 ft.
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 New York:
- Ultrasonics don't work. Birds can't hear them.
- There have been mixed results with the grid-wire system.
For more information:
- See the Cornell Laboratory
of Ornithology (Crow)
- "Controlling urban crow roosts with taped distress calls," U.
of California publication 21561, includes a tape of the calls. Contact:
University of California
ANR-Communication Services
6701 San Pablo Ave.,2nd Fl., Oakland, CA 94608
(510) 642-2431
email: jerry.hendrex@ucop.edu
http://anrcatalog.ucdavis.edu
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