Shiluach Haken

I found a dove nesting in a public restroom at night. Can i go back and do the mitzva of shiluach haken or did i miss out?

Shalom!

Thank you for your question.

The mitzva of “shiluach hakan” is a very special mitzva and you should be excited at the opportunity to be able to fulfill it! Allow me to include some important and maybe lesser-known information about shiluach hakan and performing the mitzva.

As you allude to in your question, allow me to begin by emphasizing that only kosher birds are eligible for the mitzvah of shiluach hakan. Nevertheless, even birds that are not eaten are still eligible for the mitzva as long as they have the physical signs of a kosher bird. As such, the mitzva may be performed on pigeons, doves, geese, ducks, sparrows, robins, cardinals, and orioles. The mitzva is not performed with clearly non-kosher species of birds like eagles and ravens.

The mitzvah is only performed with sending away the mother bird. The mother bird is usually found on the nest at night. As such, night is the preferred time to perform the mitzva to better ensure it is the mother bird one is sending away. The mother must be sitting on the eggs or chicks. If the mother is merely flying above them (and not actually touching them) there is no mitzva to send her away.
It is important to note that when approaching the nest some times the mother bird flies away even before you actually got a chance to perform the mitzvah, so it is advisable before you approach the nest to have in mind to perform the mitsvah however the mother bird will fly away even if it flies away when I merely approach the nest.
Once you send away the mother bird make sure she flew away and isn't still around the nest, one should lift the chicks or the eggs 3 Tefachim in order to acquire the eggs. and then you will have fulfilled the mitzvah. If it's chicks then some may want to take care of them afterwards, but one doesn't have to.

You did not forfeit the mitzva even though you did not perform it at your first opportunity. You may go back and do it again. But do note that the mitzva must be done before the chicks are able to fly on their own – usually two weeks after hatching. The nest must be on public property and ownerless, even if it is on one's property it is considered ownerless since a person has no intention to acquire the nest.  The mitzva is not performed on Shabbos and Yom Tov. Both men and women may perform this mitzva.

Sefer HaChinuch 545; Y.D. 82:3; Y.D. 292 and commentaries. Azamroh Lishmecho Hilchos shiluach Haken