Reference for Parah 2:4

שָׁכַן עָלֶיהָ עוֹף, כְּשֵׁרָה. עָלָה עָלֶיהָ זָכָר, פְּסוּלָה. רַבִּי יְהוּדָה אוֹמֵר, אִם הֶעֱלָהוּ, פְּסוּלָה. וְאִם מֵעַצְמוֹ, כְּשֵׁרָה:

If a bird rested on it, it is valid. If a male mounted it, it is invalid. Rabbi Yehuda says: If one caused [the male] to mount, it is invalid. If [it mounted] on its own accord, it is valid.

Jastrow

Jastrow