From the NY Times:
During mosquito-breeding season, from April to October, standing water on the ground, in roof gutters, on swimming pool covers and in discarded tires, among other places, can violate Article 151, which covers pest prevention and management. Health officials said the 699 summonses issued last year was about average.
In a city where Mayor Michael R. Bloomberg has all but banned smoking and waged war on soda and trans fats, some New Yorkers may complain that the crackdown on birdbaths is yet another intrusion by the nanny state or a ruse to raise more money for municipal coffers.
Mosquitoes that carry the West Nile virus lay their eggs in standing water, although exactly what constitutes standing water is ambiguous. Asked to explain the difference between standing and stagnant, a department spokeswoman, Chanel Caraway, gamely said: “Standing waters become increasingly stagnant with time as they become more and more concentrated with decomposing organic material, which is food for the mosquito larvae.”
Ms. Caraway emphasized that the agency is not necessarily anti-birdbath. “The health department will issue a notice of violation for standing water in a birdbath only if that water is stagnant, not simply for having water in a birdbath,” she said. “The decomposed organic matter found in stagnant water is the food for mosquito larvae. The department recommends replacing the water in the birdbath every two to three days to prevent mosquito breeding.”