Bava Metzia 102a: Doves that live in a dovecote or an attic are subject to the law of sending away the mother before taking the eggs (because they are considered ownerless), but the Sages forbade stealing them in order to keep the peace.
ב”א קב ע”א יוני שובך ויוני עלייה חייבות בשילוח, ואסורות בגזל מפני דרכי שלום.
Rav Eliyahu Dushnitzer served as Rosh Yeshiva and Mashgiach in Yeshivas Lomza in Petach Tikva, and many Torah giants – among them Rav Elazar Menachem Shach zt’l, Rav Shalom Schwadron zt’l, and Rav Chaim Kanievsky – viewed themselves as his privileged students. Livelihood was not easy to come by in those days, and Rav Eliyahu’s revered wife supported the family by selling chickens. She ran a stall in the marketplace, and the Rav noticed that there was a certain cat that persistently roamed around the chicken stall, eating up the scraps left behind. After his wife passed away, Rav Eliyahu worried that he had halachically inherited the cat, in which case he was obligated in all laws of damages. He subsequently gathered three men together, pronounced the cat “hefker”, and sent it on its way.
Source: http://www.tog.org.il/en/Article.aspx?id=271
[Here are three approaches to understand this story:
- Just as the Sages viewed the doves as property of the dovecote owner for the purposes of stealing, they are also considered his “ox” and he must pay for any damage they cause. Similarly, if a stray cat roams around your property and you consistently feed it, it becomes yours Mid’rabanan and you must pay for any damage it causes. The proof that you are liable for damages is from the Mishnah in Bava Basra 23a, where it says that a dovecote must be kept at least 50 amos from the city, so that the doves shouldn’t eat other people’s food. One might argue that the Mishnah is referring to doves that were actually owned on a Torah level (e.g. he originally kept them in cages and made a kinyan on them, and only later he housed them in a dovecote where they were free to come and go). However, the Rambam clearly learns that it’s talking about doves that are owned Mid’rabanan, because in Hilchos Gezeilah 6:7-8 he brings that halacha that stealing doves in Rabbinically forbidden, and in the very next halacha, halacha 9, he brings the Mishnah in Bava Basra that one must prevent his doves from doing damage. So clearly, when you own an animal Mid’rabanan, you are liable for damages too.
- The Gemara in Bava Kama 56b says that if Reuven takes Shimon’s sheep and places it in Levi’s field, and it proceeds to eat the crops, Reuven must pay. This is called מעמיד בהמת חבירו על קמת חבירו. Here too, although Rabbi Eliyahu Dushnitzer’s wife was not the owner of the cat, since she caused it to come to the area, she was responsible, and now he had inherited that responsibility. The trouble with this explanation is that if so, declaring it ownerless would not help. It was already ownerless. The issue was that she brought it there.
- Perhaps since the cat helped Rabbi Eliyahu Dushnitzer’s wife clean up the scraps, she was happy that it came, and therefore had intent to acquire it through the fenced-in area where her chickens lived – קנין חצר.]
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