Pigeons

When the Passenger pigeons, who used to fill the air in their millions, began to vanish from the skies, ignorant people refused to admit that such an animal could even become extinct. "They've gone to Australia," the deniers would say, staring at skies that once would be darkened by the movement of flocks as vast as frontal clouds.

And still the Holocaust deniers spew their shit in the face of evidence: