Tractate Kinnim - Chapter 3 - Mishnah 2 קינים פרק ג׳ משנה ב׳

If one [pair] belonged to one woman and two [pairs] to another, or [even] three [pairs] to another, or [ten] pairs to another or a hundred to another, and he offered all of them above, then half are valid and half are invalid. [Similarly], if he offered all of them below, half are valid and half are invalid. [If he offered] half of them above and half below, then the [number of birds as there is in the] larger part are valid. This is the general principle: whenever you can divide the pairs [of birds] so that those belonging to one woman need not have part of them [offered] above and part [offered] below, then half of them are valid and half are invalid; But whenever you cannot divide the pairs [of birds] without some of those belonging to one woman being [offered] above and some below, then [the number as there is in] the larger part are valid.