Daf Yomi - Beitza 10 - First Brood

Bais Shamai maintains that one cannot take a dove from its nest on Yom Tov unless those doves were moved about prior to Yom Tov. The Gemora explains that declaring orally that he wants to slaughter these doves on Yom Tov is not sufficient. The explanation given is that Bais Shamai is referring to the first brood of doves that are born that season which generally are kept as company for the mother. The mother will leave the nest if those doves disappear. We are concerned that he might change his mind from using these birds and will handle them on Yom tov unnecessarilly. Moving them about before Yom Tov ensures us that he will not change his mind.

Mishna Berura (497:31) notes that Bais shamai will permit shechting the doves on Yom Tov even if he moved about the nest prior to Yom Tov and certainly if he handled the doves.

I am a little perplexed at to why moving about the nest would be sufficient. Would that be a proper indication that he is resolute on taking those first brood doves? If there are other doves in there at that time, it would seem that one would be required to handle the doves themselves for otherwise he is not indicating that his intention is to take the first brood.