Excellent advice! I have now sent an email to the Toronto Humane Society's volunteer program known as "Toronto Street Cats". They in turn work with an organization known as the Toronto Feral Cat TNR Coalition. TNR stands for "Trap-Neuter-Release". Apparently if these organizations can trap the animals, both the Humane Society and the city's Animal Control offer free spay/neuter services. The policy is to then return the cats to their colonies. Sounds like the best hope for the cats, but not the birds. I am sceptical however that anyone would be able to trap a cat on the spit without endangering the other wildlife. The Toronto Conservation Authority is not likely to allow anyone to set traps out there.