American Crow / Meryle Ardagh / Great Backyard Bird Count
Crows and ravens belong in the Corvid family (which includes jays and magpies) and are considered to be among the most adaptable and intelligent birds. Its coal-black coloring, highly social behavior, and distinct call make the American crow (Corvus brachyrhynchos), also known as the common crow, one of the most frequently seen and heard birds. Although most bird books recognize populations along the coast and around the Puget Sound to be a distinct species called the Northwestern crow (Corvus caurinus), some experts classify the smaller Northwestern crow as a subspecies of the American crow.
Update: “On June 30, 2020, the American Ornithological Society, which maintains a formal checklist of all North American birds, announced that it was officially absorbing the Northwestern Crow (Corvus caurinus) into the American Crow (Corvus brachyrhynchos).” – “Why the Northwestern Crow Vanished Overnight” – Audubon.org
Crows will occupy almost any woodland, farmland, orchard, or residential neighborhood, as long as sufficient shelter and enough trees suitable for nesting are available. They seem to prefer lower elevations and moist places, including creeks, streams, and lakeshores.
Ravens (Fig.2) appear similar to crows and are found throughout Washington, except in major urban areas where competition from crows and a lack of nesting sites are probably too great. Ravens replace crows in mountainous areas, deserts, and rimrock areas; they are thus more common than crows east of the Cascade Range.
In recent years, crow populations have expanded into urban and suburban areas. Their tameness becomes notable as they seek the plentiful food sources found on roadsides, parking lots, ferry landings, marinas, and other places where humans influence the landscape.
Facts About Crows
Food and Feeding Habits
- Crows are omnivorous and eat whatever is available—insects, spiders, snails, fish, snakes, eggs, nestling birds, cultivated fruits, nuts, and vegetables. They also scavenge dead animals and garbage.
- Crows are known to drop hard-shelled nuts onto a street and then wait for passing automobiles to crack them. Similarly, along the coast, they drop mussels and other shellfish on rocks to crack the shells and expose the flesh.
- Outside of the breeding season, crows travel as far as 40 miles each day from evening roost sites to daytime feeding areas.
- Crows usually post “sentries,” who alert the feeding birds of danger.
Nest Sites and Shelter
- Nests are built 15 to 60 feet above ground in tall coniferous or deciduous trees. Nests are 1½ to 2 feet in diameter and solidly built in the crotch of a limb or near the tree trunk.
- In areas that lack tall trees, nests may be placed lower in hedgerows or shrubbery. In urban areas, crows may nest on window ledges or the sides of buildings.
- Nests are constructed from branches and twigs and are lined with bark, plant fibers, mosses, hair, twine, cloth, and other soft material.
- Hawks and owls inhabit old crow nests; raccoons and tree squirrels use them as summer napping platforms.
Reproduction and Family Structure
- Both sexes build the nest during a period of 8 to 14 days—beginning as early as mid-March and as late as mid-July—depending on latitude and elevation.
- The female incubates four to five eggs for 18 days, at times being fed by her mate or sometimes by offspring from the previous year.
- The chicks grow quickly and are out of the nest at around four weeks after hatching, although they continue being fed by the adults for about another 30 days.
- Frequently, one or more young crows remain with the parents through the next nesting season, or several nesting seasons, to help care for nestlings. This cooperative behavior during breeding includes bringing food to the nest and guarding the nestlings.
- In spring and summer, crows are usually seen in family groups of two to eight birds. During late summer, fall, and winter, crows gather from many miles to form communal night roosts.
Mortality and Longevity
- Adult crows have few predators—eagles, hawks, owls, and human hunters—with humans being their main predator.
- The causes of death of young crows still in the nest include starvation, adverse weather, and attacks by raccoons, great horned owls, and other animals.
- Mortality in the first year is about 50 percent, but adults live six to ten years.
Much of the time, crows are seen in small, noisy, family bands, spending the majority of their time in fairly restricted areas. For about a month during the nest building, egg-laying, and incubation periods, breeding adult crows become uncharacteristically secretive and quiet. After the eggs have hatched, the parents become noisy defenders of their nest and later the young are heard wailing at their parents for food with an insistent, nasal caw.
In late summer through winter, crows are seen in large, raucous flocks that roam widely. In agricultural areas, hundreds of crows may gather to forage in fields, while in cities, crows may seek human-provided food sources as well as foods acquired through natural foraging.
Interesting visual displays include male and female crows bobbing their heads up and down, and accentuating this by bowing. The wings and tail may also spread slightly and the body feathers may be fluffed. The bobbing display is usually performed in the presence of another crow in spring, and is possibly associated with courtship. Males may also engage in diving flight displays, chasing females.
Crows mob owls, hawks, and eagles throughout the year and are in turn mobbed by smaller birds. The loud, excited calls of crows are very characteristic and may lead you to sighting a local bird of prey.
Even though crows are common, their nests are not easy to locate, except after deciduous trees lose their leaves. In addition to being secretive nesters, crows may partially construct a number of preliminary or decoy nests.
Crows return to the same nest territory year after year, often a few weeks before they start building. If a small group of crows remains in a particular area day after day, this may signal that nest building is about to begin.
Many larger twigs that form the base of the nest are broken directly off trees. If you see a crow hopping slowly about in some dead branches, continue to watch and you may see it break off a branch and carry it to the nest. This is the best time to try to find nests, as the birds are less secretive than during egg-laying and incubation.
When the nesting period is over, the family group usually joins other groups of crows in communal night roosts. Roosts reach their highest numbers in late winter and may contain hundreds or even thousands of birds. Roost sites are generally located in groups of trees, often near water, and are used for many years if they aren’t disturbed.
Communal roosting helps crows exchange information and find mates. Some birds, because of their age or familiarity with the surrounding landscape, are more efficient at finding food. Less experienced members of a roost can follow other birds to known feeding sites. Communal roosting also helps crows remain safe and warm. Crows occupying the center of the roost are less exposed to predators and weather than those on the edges or those roosting alone.
Crows are believed to return to the same roost each night, and their behavior is often predictable. Each morning the roost breaks up into smaller flocks that disperse across the landscape to feed. In mid-afternoon, these smaller flocks start back toward the communal roost. They fly along the same flight lines each day and are joined by other flocks as they go. Often there are pre-roosting sites, where flight lines coincide and crows stop to feed before flying the final distance to the roost. Communication between groups of crows often takes place at these pre-roosting sites.
If you are near a flight line for as long as an hour, you will notice crows passing overhead, a few to several hundred at a time in the late afternoon.
The normal crow call is a loud caw or awk. The male also makes a dry, rattling call, very different from the normal call. If you are very fortunate you may hear the soft, almost melodious song of the crow.
Tracks and Trails
Crows spend a lot of time on the ground and tracks can be seen in snow, mud, or in wet sand at low tide (Fig. 4). Despite the fact that “crow footed” is a term used to describe people who walk with their toes pointed inward, crows (and ravens) usually leave relatively parallel tracks.
Figure 4. The four toes in a crow’s track are about the same length, and in good prints each toe leaves a claw mark at the end. Three thick toes point forward, and one long toe (equally thick) points back. The total length of a print is approximately 3 inches. (From Pandell and Stall, Animal Tracks of the Pacific Northwest.)
Crows help control pest insects and “clean up” dead animals and garbage that has been scattered by other animals. Although crows prey on songbirds and their young, research suggests that they do not ordinarily have a significant impact on songbird populations. Robins, for example, have evolved to have two to three clutches each year to make up for young lost to crows. However, because crows are intelligent, opportunistic, and protective of their young, and at times congregate in large numbers, people should be mindful of how their actions may attract or affect crows.
To prevent conflicts or remedy existing problems:
Keep crows out of the trash. Crows are often blamed for spilling garbage, trash, or grain that was actually spilled by raccoons, dogs, or other animals seeking food. To prevent other animals from making garbage available to crows, try these techniques:
- Keep your garbage-can lid on tightly by securing it with rope, chain, bungee cords, or weights.
- Buy garbage cans with clamps or other mechanisms that hold lids on.
- To prevent tipping, secure side handles to metal or wooden stakes driven into the ground.
- Keep your cans in tight-fitting bins, a shed, or a garage.
- Put garbage cans out for pickup in the morning, after raccoons have returned to their resting areas.
- Don’t leave trash bags alongside a curb, in the back of a pickup truck, or in an overfilled bin.
- Ask your local restaurants and food chains to keep their garbage containers closed.
Crows are early risers and will visit unattended garbage at first light or shortly thereafter.
Know your nest boxes. Crows are capable of pulling nestlings out of nest boxes. They are most apt to snatch an older nestling that sticks its head out of the hole to accept food from its parents, but will also poke their heads into nest box entrance holes. This is a learned behavior that can result in individual predatory birds making the rounds of boxes and causing many losses of nestlings, and teaching other individuals to do the same.
To prevent this:
- Never put up a shallow box; ensure the nest box has at least 6 inches from the entry hole to the bottom of the box.
- Clean out used nests annually so the nesting birds do not fill the lower part of the box.
- Choose a box designed without a perch or ledge under the hole. The nesting bird doesn’t need it and perches give predators better access to the eggs or nestlings.
Dive Bombing Crows
Most aggressive behavior from birds is motivated by defense of their territory or young, or their search for handouts.
In the spring and summer crows and other birds establish territories, build nests, and rear young. During this period, adult birds may engage in belligerent behavior, such as attacking creatures many times their size. In this case, the birds are simply trying to protect their homes, their mates, or their young.
When possible, stay away from nesting areas with aggressive birds until the young are flying (three to four weeks after eggs hatch) and the parents are no longer so protective. Do not attempt to “rescue” chicks found outside nests when adult birds are calling loudly nearby—see “Baby Birds Out of the Nest” for information. If you must walk past a nest, wave your arms slowly overhead to keep the birds at a distance. Other protective actions include wearing a hat or helmet or carrying an umbrella.
Figure 2. Crows
Figure 3. Ravens have wedge-shaped tails and crows have fan-shaped tails. This isn’t very easy to see if the bird is sitting on the ground, but when it’s flying overhead, you can often get a good look at the shape of the tail. (Drawing by Jenifer Rees.)
Ehrlich, Paul R., et al. The Birder’s Handbook: A Field Guide to the Natural History of North American Birds. New York: Simon & Schuster, 1988.
Nehls, Harry B. Familiar Birds of the Northwest: Covering Birds Commonly found in Oregon, Washington, Idaho, Northern California, and Western Canada. Portland, OR: Audubon Society of Portland, 1989.
Morse, Robert W., et al. Birds of the Puget Sound Region. R.W. Morse Company, 2003.
Peterson, Roger Tory. A Field Guide to Western Birds. Boston: Houghton Mifflin, 1990.Washington, DC: National Geographic Society, 2002.
Udvardy, Miklos D. F. Audubon Society Field Guide to North American Birds–Western Region. New York: Alfred A. Knopf, 1977.Internet Resources
Written by: Russell Link, Urban Wildlife Biologist
Content provided by and with permission from Russell Link WDFW.