Kinnim 2:1-2

Kinnim 2:1

If one bird from an undesignated set flew away, or if it flew among birds that were left to die, or if one of the birds died, then a replacement is added to the remaining bird. If it flew among birds that are to be offered, it is invalid and it invalidates another bird as its counterpart. This is because a bird that flies away invalidates both itself and another bird as its counterpart.

Kinnim 2:2

For example, if two women each had two sets of birds and one bird flew from one woman’s set to the other’s, then it invalidates one of the other birds through its departure. If it flew back, it disqualifies another bird through its return. If it flew away and returned, flew away and returned, then no loss is incurred because even if they were all mixed together, there would not be fewer than two.