Every morning, the Temple service started with removing a small portion of the ashes from the Altar and placing them at the southwestern corner of the Altar, where they were swallowed into the ground. Since there was this mitzvah of “separation of ashes,” that continued, there remained a prohibition of misappropriation for the ashes. In contrast to the ashes of this outer Altar, the ashes of the inner Altar, which was used for burning the daily incense, lost the misappropriation prohibition once they were burned. However, they were put on the place where the outer Altar ashes, and after they were mixed, the prohibition of misappropriation was again in force.
Bird sacrifices, turtledoves and pigeons, had to be of specific age: turtledoves – older than a year, and pigeons – younger than a year. Therefore, if turtledoves were too young, or pigeons were too old for the sacrifice, there was no prohibition of misappropriation for them. There Sages established a prohibition not to use them, but there are no Torah-imposed penalties if one does.
Rabbi Shimon disagrees on the last point: turtledoves whose time for a sacrifice has not yet arrived nevertheless have a prohibition of misappropriation: since they eventually will come of age, there is a prohibition of misappropriation even now. This is not true for pigeons older than year, since they will never become younger, but only older.
Art: Jan Victors - A Still Life With A Couple Of Pigeons Nesting And Preening Together With Four Chicks