For anyone who hops, if when it turns, it sees its nest, it hops - דכל דמידדי אי הדר חזי לקיניה מידדי
Summary:
The reason the גמרא states that a bird will not be מדדה if it cannot see its nest, is to explain why we are not concerned for רובא דעלמא even if it is a case where the שובכין דעלמא are בין הכרמים, or even if they are less than נ' אמה from the bird.
Abayay said; we also were taught in a Mishnoh, blood which was found in the corridor is Tohmay, etc. - אמר אביי אף אנן נמי תנינא דם הנמצא בפרוזדור טמא כולי
Summary:
The דם is טמא if it is found behind the לול.
Summary:
We can be 'גורס 'דתני, saying that the גמרא is citing ר"ח to bolster the proof of אביי, or that indeed רבא is saying it that it proves רוב ומצוי, for otherwise what is the חידוש of ר' חנינא.
And we know from this there is support for Rabi Zayroh - ושמע מינה איתא לדרבי זירא
Summary:
The fact that we are not גוזר by דם where it was found מן הלול ולפנים on account of מן הלול ולחוץ assures us that we are not גוזר by ט' חניות that שמא יקח מן הקבוע, therefore one רוב is sufficient, since there is no גזירה.