(These can often be found next to an apartment house's dumpster.)

I obtained one recently and harkened back to a use I saw at the Audubon
Society of Western Pennsylvania.

You line the remaining three sides of the aquarium with reflective window
film and fashion a wooden lid for the result. Now take the modified fish
tank and mount it in the window next to your breakfast table, missing side
out.

Each morning open the wooden top and dump in some bird seed. Replace the
lid.

Presently little birdies will come for their breakfast while you enjoy your
coffee not more than a foot away.