2,603. Shiluach HaKein

Hilchos Shechita 12:17

The day that we’re discussing in the context of “it and its young” is the night followed by the day. Accordingly, if one slaughtered the first animal on the start of Tuesday night (i.e., the eve of Wednesday), he may not slaughter the other animal until the start of Wednesday night (i.e., the eve of Thursday). Similarly, if he slaughtered one at the end of Wednesday, before twilight, he may slaughter the other at the start of Wednesday night (i.e., Thursday eve). If he slaughtered the first during twilight on Wednesday (which might already be Thursday), he may not slaughter the second until after night has fallen on Thursday (i.e., the eve of Friday), though if he slaughtered it on Thursday during the day, he does not receive lashes.

Hilchos Shechita 13:1

If someone takes a mother bird with its young and slaughters them (which shouldn’t be done), the meat may be eaten but he is liable to the penalty of lashes for slaughtering the mother as per Deuteronomy 22:6, “Do not take the mother with her young.” If it died before he could send it away, he is similarly liable to lashes but if he sent it away after taking it, he isn’t liable.