(This at GrrlScientist Blog. My post:
Domestic cats are a pet species which has evolved to rely on humans over thousands of years. This makes their abandonment or re-abandonment animal cruelty and inhumane. Their presence outdoors is entirely an environmental issue, not an animal welfare one. There is nothing compassionate, non-lethal, nor humane about their murder of our wildlife, I've watched it in my own yard for years. Anyone abandoning them or enabling them to murder protected wildlife should be prosecuted.
It will take a committed organization of birders, biologists, ecologists, and other concerned citizens to overcome the pandering and myths of the cat enablers and apologists.