What is the ruling on throwing sick birds while they are still alive?

Whoever owns a bird and cages it, its sustenance and gentle treatment become obligatory upon him. If the bird is able to move and its food is available, then there is no harm in releasing it. However, if it is unable to move, it is not permissible to throw it away alive; rather, it must be kept and cared for or slaughtered, unless its disease is contagious, in which case the competent authorities must be informed.