Watch the Birdie
Ahron Einhorn wrote:
In Ask the Rabbi #83 you wrote how the mitzvah of sending away the mother bird applies only to eggs that are ownerless. You wrote an anecdote about the bird's nest in your awning where you said: "the mitzvah didn't apply, because the nest was on my property." Here in LA we do the mitzvah with birds on private property as long as the owner says he doesn't want to acquire the birds. You may also want to caution people that they need to be able to recognize the bird's gender.
People generally want to acquire anything of value found on their property. But you're right: If you declare "I don't want to acquire eggs laid on my property" then the eggs remain ownerless and you can fulfill the mitzvah of 'sending away the mother bird.'
Actually, most city-dwellers today would probably see the eggs more as a nuisance than a valuable asset. They would much rather do the mitzvah than acquire the eggs. I asked Rabbi Zalman Nechemia Goldberg, shlita, who agreed that today one would not necessarily acquire nest eggs automatically.
As you mentioned, the mitzvah is to send away the mother, not the father. Another limitation: It applies only to kosher birds. Sending away the father or sending away an unkosher bird for no reason would be a transgression of 'tza'ar ba'alei chaim' - causing pain to living creatures.