Birds. We hate the damned things. Always shitting on our cars. Always making noise when we're trying to sleep. Always infecting us with deadly strains of the flu to make sure we die a slow and very horrible death.
Remember when bird flu was going to kill us all? How'd that work out for ya? Now it's swine flu, but don't tell that to b-movie makers because death by pig is a bit harder to take seriously than death by bird for some reason. Birdemic does not feature a virus, unless the American Medical Association has officially declared Alfred Hitchcock Rip-off Syndrome a legitimate disorder.