It has become a common practice to put stale cat food and other food scraps into the mesh bags that onions are sold in and tying the bags outside for birds. This can be dangerous for birds, because their feet or legs can become trapped in the mesh.
Birdseed can be mixed with the stale cat food for the birds. People should be careful about leaving cat food outside for birds since cat food can attract raccoons. A property near a population of raccoons with cat food outside for stray cats or for birds can quickly be overrun with raccoons which can carry rabies and their notorious for making messes by overturning trash cans.