Crows |
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History and Biology The Crow is a member of the family Corvidae with Ravens, Jays, and Magpies. The Corvidae probably originated in Australia from a common crow-like ancestor. It is now found worldwide and most terrestrial habitats including deserts and the high Arctic are home to at least one species. The mostly black Crow and Raven comprise half the Corvidae family and are found worldwide except for the neotropics, south of Mexico . It is difficult to distinguish between the Crow and the Raven. Voice is usually the best differentiation. The Crow is a large perching bird with rounded wings and tails. The wings of the Crow and Raven are slotted between the primaries when the wing is extended. This allows for extra lift and allows the crow to soar long distances looking for food. As do all members of the Corvidae family, it has strong bills and feet. The legs are scaled anteriorly and smooth posteriorly. The Crow, as well as other Corvids, is bold, noisy, and gregarious. The crow, as is the raven, is an opportunistic scavenger. A crow will scavenge surfaces of plants and the ground for readily available food, but it also has an inherent high level of intelligence which enables it to uniquely obtain food in cleverly industrious ways. It has even been observed using tools to obtain food. Urban crows will frequent dumpsters, compost piles, and other sources of human waste. Many crows have become skilful at opening plastic bags to obtain food. The crow is monogamous and breeds at approximately 3-5 years of age. Both sexes help build a nest of sticks with woven lining in a tree. The female will raise one brood per year of 3 to 8 eggs. The chicks are altricial and may have down. They fledge at 18 to 40 days. Both sexes feed and care for the chicks. The young may stay with parents in a family unit for several years. Some families consist of 15 individuals. All may assist in raising young. Annual survival is 75% to 90%. The crow may live for several years. The oldest Corvid on record is 17 years 7 months. Public Health Damage: Crows create a serious and constant health problem. They may be a reservoir for the transmission of diseases to humans (zoonotic diseases) such as ornithosis, salmonellosis, several forms of encephalitis (West Nile Virus), histoplasmosis, cryptococcosis, toxoplasmosis, and coccidiosis. The Crow and Jay have become the bioindicators for the presence of the West Nile Virus in an area. Sick or dead Crows should be reported to the local Department of Health for testing. Crows are also a concern to farmers because they may carry and transmit many diseases, such as hog cholera, for livestock. Structural Damage: Crows may roost and feed in large flocks thereby defacing equipment, statues and buildings with excretory droppings. They also cause structural damage to agricultural barns and silos. Agricultural Damage: Crows threaten the health of livestock in United States agriculture because they may be a reservoir for the potential transmission of many livestock diseases such as salmonella, hog cholera, and encephalitis (West Nile Virus) especially around concentrated poultry and swine production facilities. They also do damage through the consumption and contamination of agricultural seed and grain products in the field, storage facilities, and wholesale and retail outlets. Environmental Damage: Because of their commensal relationship with humans and their potential for producing large flocks, Crows are a serious and constant public health and property damage problem. Economic Damage: Economic damage from Crows is difficult to assess when you consider the intangible costs of the impact of zoonotic diseases on the public health of humans, livestock, and wildlife. Also there is a significant cost to American consumers and business from the consumption and contamination of seed and grain damaged by Grackles. References: Coded Federal Registry, 50CFR17.Subpart D, Endangered and Threatened Wildlife and Plants Coded Federal Registry, 50CFR 20.43, Wildlife and Fisheries, Hunting and Migratory Bird Regulations Coded Federal Registry, 50 CFR 21.43 Subpart D, Control of Depredating Birds
Fergus, C., 2000, Wildlife of Pennsylvania and the Northeast, Stackpole Books, Mechanicsburg , PA 17055 Oklahoma Wildlife Conservation Commission, 2004-2005, Oklahoma Hunting Guide, Protected Species. Page 9. Oklahoma Department of Wildlife Conservation, P.O. Box 53465 , Oklahoma City , OK 73152 . Sibley, D.A., 2001, The Sibley Guide to Bird Life and Behavior, National Audubon Society, Alfred A Knopf, N.Y. Texas Parks and Wildlife Department, 2004, Hunting and Fishing Regulations, Endangered, Threatened, and Other Protected Nongame Species, Protected and Unprotected Birds, Texas Parks and wildlife, 4200 Smith School Road, Austin, Texas 78744. Wernert, S. J., 1982. North American Wildlife, The Reader's Digest Association, Inc. Pleasantville , N.Y. |
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