Crows and Their Night Roosts
In volume II of his three volume masterpiece on the birds of Massachusetts, the former State Ornithologist, Edward Howe Forbush quoted Henry Ward Beecher as once saying that if men wore feathers and wings, very few of them would be clever enough to be crows. While this claim was meant as nothing more than a humorous exaggeration, many ornithologists today, nonetheless, believe that members of the crow family, a family that includes all species of crows, ravens, magpies and jays, are among the most intelligent of all birds.
During late March and April, breeding and nest building begins. Crows begin a number of nests, usually in the crotch of a tall tree, before completing the one that will be used.
Nonbreeding young from the previous year, and possibly the year before, stay with the parents to become nest helpers. The number of helpers can vary from three to six. It is unclear whether or not they help feed the nestlings, but they have been observed aiding in nest building and feeding the incubating female.
In Massachusetts the eggs are usually laid between early May and mid-June. An average of 3 to 6 eggs are laid followed by an 18 day incubation period. The young are fed by both parents during the four to five week nestling period and are foraging for food on their own two weeks after that.
Crows are almost completely omnivorous, meaning they eat a wide variety of food types. These are known to include many fruits, nuts, grains, insects, crustaceans, mollusks, amphibians, reptiles, small mammals, birds and their eggs and nestlings, garbage, and carrion (e.g., roadkills, dead fish, etc.). In residential areas, crows have learned to tear open trash bags placed on the curb prior to rubbish day and to "rototill" lawns in search of grubs.
Crows, as well as other family members, cache food - that is, they hide food away in niches, nooks and crannies (such as knotholes in trees) to provide themselves with a ready food supply during food shortages.This means they must have fairly well developed memories, which suggests a relatively high degree of intelligence.
Crow are said to be able to count (to a point). Many hunters have told stories of crows avoiding hunting blinds until all the hunters that they have watched enter a blind have left. Also, crows are known to be very discriminating in their abilities to identify specific objects. For example, they may closely approach a person with a fishing pole, but will carefully avoid the same person if they are carrying a gun. Such accounts are common because crows have long suffered under the reputation of being "bad", and consequently have been shot, poisoned, and otherwise persecuted.
Crows' negative reputations have followed them over the course of many centuries of cohabitation with humans. The bases for this reputation are many, and they probably apply equally to various other large, black birds, such as cormorants, which have also been undeservedly vilified and maligned. Most species of crows (all four species in North America) are black, and the color black, historically, has often been associated with night and the unseen. Also, crows have always been crop raiders; they frequently steal eggs and chicks from the nests of other species of birds; and they also have been known to steal shiny objects such as articles of jewelry from humans. The reasons for this latter behavior remain obscure.
Crows and their relatives (especially ravens) possess one of the most highly varied vocal repertoires of any group of birds. They are capable of uttering far more than the "caw" call with which many people are most familiar. This vocal range no doubt accounts or crows' impressive capacity for imitation. Captive birds, particularly, have been known to imitate many sounds including car horns, barking dogs, and human speech - all without their tongues being split, despite the myth that only birds so maimed can "speak."
WHAT IS A ROOST?
Roosts are areas where birds sleep at night. The American Crow is well known for forming large communal roosts, which may be comprised of thousands of individuals, in the non-breeding season. Large flocks of crows gather in late afternoon in pre-roost staging areas, moving on in groups to the final roost location. These gatherings can be cacophonous, and are often the source of much consternation among human residents who find themselves sharing their neighborhoods with roosting crows. No doubt, the public's flames of suspicion and fear of crows were fanned by Alfred Hitchcock's classic film, The Birds, though the murderous behavior such as that portrayed by the hundreds of trained birds in the movie is nonexistent among birds of any kind. Crows are harmless to humans and pets, unless the pets are as small as mice are.
CROW ROOST LOCATIONS
The stand of trees, deciduous or coniferous, chosen by American Crows for their nightly gatherings can be located anywhere, including within densely populated, residential or industrial neighborhoods.
Crows will travel up to fifty miles to their night roost, which can contain hundred to tens of thousands of individuals. They may also gather in "staging areas" along the route before flying to the roost site just before sunset. When in the vicinity of a night roost, anyone looking skyward a hour before sunset may see hundreds of crows arriving at the site from all directions. In the morning, at first light, the birds begin to nosily communicate with one another before dispersing to their respective foraging areas.
In late February or March, these large roosts begin to break up and the mated pairs disperse to their home territories to begin nest-building while unmated birds may continue to use the roost for several more weeks.
OTHER SPECIES THAT ROOST COMMUNALLY
European Starlings gather in communal roosts throughout the year in numbers ranging from a few hundred to tens of thousands of birds. The roosts are largest in the late summer when the young, as well as the parents, gather at the site. Their preferred sites are beneath bridges, in vacant buildings, or in trees.
Another gregarious bird, the House Sparrow, nests, feeds, and roosts in flocks. The sizes of the flocks peak in the fall when the young birds and the adults join together to feed on the abundant seeds and to roost at night. The roosts are usually in trees, shrubs, or vines with dense foliage or in sheltered locations on buildings; both areas offer them protection from wind and predators.
Red-winged Blackbirds, Brown-headed Cowbirds, and Common Grackles (in the subfamily Icteridae, a word derived from the Greek ikteros, meaning to gather) form roosts containing thousands of birds during their spring and fall migrations.
Chimney Swifts gather by the hundreds at dusk, circling over a favored chimney. Almost in unison, they funnel into the chimney where they cling to the inside walls until dawn.
SITUATIONS AND SOLUTIONS
As people understand roosting behavior, their fears and anxieties may be allayed to the point that they become more tolerant. In any case, there is little that can be done to change things - hundreds of birds roosting in trees 50 or 60 feet high are not easily frightened or discouraged.
TECHNIQUES THAT DO NOT WORK
It is a waste of money to attempt to discourage birds at a communal roost by hanging fake owls; birds are not intimidated by these nonthreatening statues. Also, because most birds do not have a well-developed sense of smell, odor repellants are not a solution.
When crows (or starlings) first arrive at a roost location (usually starting an hour before sunset), a loud, persistant noise such as banging on metal pots and pans or slapping two blocks of wood together, might persuade the birds to move on, especially if it is a new roost.
There are companies which sell recordings of bird distress calls, which, when played, may frighten the birds. The theory is that when the call of an alarmed crow is played nearby, the crows flying in to roost will be frightened off. Check the yellow pages under "Bird Control."
The location of the recorder must be changed every few nights so the birds do not get used to it, and it must be played for several hours each evening when the birds begin arriving at the roost site.The success of these devices is questionable, and they are unlikely to discourage a large, long-established communal roost.
BIRDS AND THE LAW
All birds are protected by federal laws under the "Migratory Bird Act of 1918," as well as by Massachusetts state laws. It is illegal to destroy, relocate or possess birds, their nests or their eggs. The only exceptions are non-native species: House Sparrow, European Starling, and Pigeon. Trained and licensed wildlife rehabilitators, who have passed a federal and/or state-administered test, are permitted to care for injured or orphaned wildlife.
Crows may only be hunted during hunting season with a license in specified areas. Many towns do prohibit hunting them and the state law does not allow hunting within 500 feet of a building except with permission. Contact the Massachusetts Division of Fisheries and Wildlife for regulations.
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