Zevahim 67: Mixed-up Post-Childbirth Bird Offerings

Bringing a burnt-offering from a bird can switch to be a sin-offering, if the procedure that is done is the sin-offering practice, instead of the burnt-offering practice. Plus, the queries of the Gemara on this with a contradictory case of two women who bring the burnt- and sin-offerings post childbirth, and what happens in the event of error or confusion.