Yerushalmi Bava Batra 2:5 ירושלמי בבא בתרא ב׳:ה׳

MISHNAH: One distances the ladder⁷⁰The permanent ladder leading to the upper floor apartment. from a dovecote by four cubits lest a marten jump⁷¹Onto the dovecote and eat the pigeons. If a builder contracts to build an access to an upper floor and disregards this rule it is malpractice and he has to rebuild the access at his own expense., and the wall four cubits from the leader⁷²By which the rainwater flows from the roof to the earth. Near the leader the earth is soft and does not support anything. so it can support the ladder. One distances the dovecote from town by fifty cubits⁷³It is axiomatic that a pigeon chick which cannot yet fly does not move farther than 50 cubits away from the dovecote. Therefore, any chick within 50 cubits belongs to the owner of the dovecote; the rule prevents property disputes about pigeon chicks.. A person may not build a dovecote on his property unless he have fifty cubits in each direction⁷³It is axiomatic that a pigeon chick which cannot yet fly does not move farther than 50 cubits away from the dovecote. Therefore, any chick within 50 cubits belongs to the owner of the dovecote; the rule prevents property disputes about pigeon chicks.. Rebbi Jehudah says, the area of four bet kor⁷⁴The dovecote has to be the center of a square of surface area 300’000 square cubits, of side length 547.72 cubits, in its owner’s possession., the distance one sends a pigeon. But if he bought it even with the area of a quarter [qab]⁷⁵A square of area 104 1/6 square cubits, of edge lengths slightly over 10 cubits; cf. Chapter 7, Note 49., it is in his power⁷⁶An existing dovecote which does not conform to the rules does not have to be removed..

HALAKHAH: “One distances the ladder,” etc., until “in his power.” Rebbi Eleazar said, that is, to the right hand side. But to the left he may put it up immediately⁷⁷If the leader is built so that the water flows to the right hand side, one may build the ladder close to it on the other side since its stability will not be compromised..

Here, you say 50 cubits. But there, you say 30 stadia. Rebbi Yose ben Rebbi Abun said, they feed within fifty cubits; they fly even four mil⁷⁸Reformulation of a paragraph in Bava qamma 7:10, Notes 105–107..