Question: Having learned the last lesson (please review it if you haven’t already), why can’t a person beat the system, by doing ‘zimun’ on ALL the birds, and then just taking the ones he really needs? Answer: If he does that, it does not work! Why? Because doing ‘zimun’ on more birds than one knows he will need is, in effect, like doing ‘zimun’ by method #3 (see above) - where he says: “I am hereby designating on Erev Yom Tov (only) those birds I will select on Yom Tov.” Recall that the reason the halacha does not allow that kind of ‘zimun’ – even though it should technically work by the B’reira principle – is because we are concerned that he will handle and inspect birds that he does not end up taking and will have thus handled muktzah.
Question: What if he doesn’t know how many he will need, e.g. he will find out only on Yom Tov how many guests will be eating with him? If a person may not do ‘zimun’ on more than he needs, how can he ever do ‘zimun’ in such a case?
Answer: Ah… One may do ‘zimun’ on as many birds as he might need! If he thinks he might need all of them, he may do ‘zimun’ on all of them, even though in the end he does not. The same is true for any number of birds he thinks he might need. In fact, since he did a legitimate ‘zimun’ on all of them, he may handle all of them, even though he does not end up taking all of them! Again, what is not legitimate is doing ‘zimun’ on more birds than he knows he will need! (Do you need me to repeat that?!)