Revised August 2001
What is the connection between the West Nile virus (WNV) and crows? WNV can infect virtually any species of bird, including crows. When crows are infected, unlike with most birds, horses or people, they tend to die. Thus, crow deaths may be an indicator of WNV activity in an area. To take advantage of this observation, Connecticut and many other states have developed systems to collect selected dead crows for testing for WNV.
Why do crows die from (WNV)?
For reasons that are unknown, a high percentage of crows that become infected with WNV develop severe infection, become ill and die. Most birds and humans develop few if any symptoms, and only a small percentage develop severe, life threatening infection.
How widely dispersed are
American crows are found throughout central and eastern North America, wintering as far north as southern Maine and the Great Lakes region.
How can I identify an American
American crows are large, black, perching birds with robust beaks and a fan-shaped tail. Both sexes are similar in appearance although females are slightly smaller.
Are crows spreading the disease to
No. Crows cannot transmit this disease to humans. They must first be bitten by an infected mosquito that must then bite a human to possibly spread the disease. Even then, most humans will not show the effect of the disease.
What should I do if I find a
The DEP and the Department of Public Health are advising residents who find dead crows or other birds to report this to their local health department during regular working hours. The local health department then may send a representative to pick up the bird or request you dispose of the bird in an appropriate manner.
What if I am told to dispose of
the bird myself?
Dead birds can be disposed of by burying (three-foot deep) or double bagging them and disposing of them with regular trash. Check with your local health department for specific instructions.
How long do crows live?
In the wild, the average life span is 7-8 years. In captivity, crows have been known to live up to thirty years.
Do crows migrate?
American crows can be considered partially migratory. They can make rather long daily movements but do not need to migrate for long distances. Crows will migrate out of areas with winter temperature averages of approximately 0F. In more temperate winter climates like Connecticut, most crows remain all winter.
How far can crows travel during
As noted above, crows can travel rather long daily distances. Daily distances of upward to 50 miles are common and distances upward to 100 miles have been documented. This long distance flight is more common in fall and winter when they form large winter roosts. During the breeding season (spring & early summer), crows do not travel as far from their nest.
Why do crows congregate (roost)
in large numbers?
For crows, large roosts are primarily a fall and winter phenomenon. Numbers peak in winter then decrease as the breeding season approaches in March. It appears all crows join in winter roosts, even territorial breeding crows. Most theories suggest crows roost because it provides protection from predators and they dont mind congregating in large numbers as some birds do.
When do crows mate?
Early spring (March) is when crows usually court and mate. After mating, females build a nest in 5 to 13 days against the trunk of a tree at heights ranging from 6 to 60 feet above the ground.
What is the history of the
American Crow in Connecticut?
American Crows are native to Connecticut. Crow populations have been increasing in Connecticut since the early 1800s due to their ability to adapt to human behavior, high reproductive potential, and opportunistic feeding habits.
Where can I go for more information?
Prepared by the DEPs Office of
Communications and Education
79 Elm Street, Hartford, CT 06106
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