The phenomenon occurs twice daily, once in the early morning and again in the late afternoon. While it doesn't compare with a solar eclipse, it's still impressive if you happen to be outdoors when it occurs. Even on a cloudy day, the sky begins to blacken and this continues for many minutes. No, it isn't a storm front moving in, but rather hundreds of crows, as the birds make their way to and from local roosting areas.
While places like Auburn, which has seen its invading crow population soar to as high as 75,000 birds, the black-feathered hoards have also taken a liking to many other cities and larger villages such as Norwich. In Albany, the birds have become so plentiful and bothersome that the Capitol's Department of General Services began using trained marksmen to try and annually control their numbers, or at least scare them away. Locals have come to call it "The Annual Running of the Crows."
All joking aside, when any wildlife species becomes too numerous, it could endanger both the overabundant species as well as other species, including humans. Avian species normally are seen as a lesser danger, compared to mammals such as deer, fox, raccoon, skunk, and rodents, the latter species being susceptible to rabies. However, when birds such as crows, geese, starlings and pigeons become too numerous, other threats increase. Being flocking species, they tend to concentrate, and as densities increase, they not only begin to foul their favored environments with their highly acidic droppings, but the opportunity for disease spreading through the flocks increases proportionately with the densities.