American Crow

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.

Nest Sites

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.

Roost Sites

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.

Calls

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.

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.