Does taking a pigeon that comes to one's home, with the intention of raising it, and then losing it, constitute a theft that necessitates expiation?

If you know, or it is highly probable, that the pigeon belongs to someone, it is not permissible to take it. If you have done so, you must seek Allah's forgiveness and repent by returning the right to its owner. If returning it is not possible due to the pigeon being lost or dead, or if its owner is unknown, then you should donate its value on his behalf, guaranteeing it to him if he is identified later and does not approve of the reward of the charity. Ibn al-Qayyim stated that whoever seizes something unlawfully and cannot return it to its owner or his heirs, should donate it on their behalf. The reward of the charity will be for the one who gave the charity. Then, if the rightful owner chooses its reward on the Day of Resurrection, he may have it; and if he insists on taking the good deeds of the one who seized it, he may do so.