What is the ruling on acting with the intention of marriage, such as putting out leftover rice for birds or preparing food?

There is no religious impediment to performing permissible acts to achieve marriage or other permissible goals. It is better for a Muslim to intend by all their actions to draw closer to Allah Almighty, thereby attaining the good of this world and the Hereafter, in accordance with the hadith: "Indeed, actions are by intentions, and indeed for every person is what they intended." Permissible acts do not yield reward unless the doer intends by them closeness to Allah.