Mosquitoes lay their eggs in moist areas, such as standing water. The eggs become larva that remain in the water until the adults mature and fly off. Weeds, tall grass and shrubbery provide an outdoor home for adult mosquitoes. They can enter houses through unscreened windows or doors, or broken screens. Many mosquitoes will breed in containers that hold water, such as flower pots or discarded tires.
Some mosquitoes are most active between dusk and dawn, when the air is calm.
However, othes will feed at any time of day. In New York State, most West Nile virus-positive birds have been American crows. The State Health Department is using dead crow sightings to track West Nile virus, so it's important to report any dead crows to your local health department. Not all dead crows need to be tested for West Nile virus. There is no evidence that birds can transmit West Nile virus to people, but gloves should be worn when handling any dead bird or mammal because of the possibility of other diseases.