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Link to original content: https://web.archive.org/web/20061105022804/http://www.mosquito.state.ct.us/fact/crowfact.htm
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?
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
Crow?
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
humans?
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
dead crow?
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
a day?
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 don’t 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 DEP’s Office of
Communications and Education
79 Elm Street, Hartford, CT 06106
08/07/00
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