Reference for Chullin 1:5

כָּשֵׁר בַּתּוֹרִין, פָּסוּל בִּבְנֵי יוֹנָה. כָּשֵׁר בִּבְנֵי יוֹנָה, פָּסוּל בַּתּוֹרִין. תְּחִלַּת הַצִּהוּב, בָּזֶה וּבָזֶה פָּסוּל:

That which makes turtle-doves proper sacrifices, renders young pigeons improper ones, and whilst these are valid as young pigeons, they cannot be used as sacrifices of turtle-doves. When the neck feathers of either kind begin to shine and to turn yellow, they are unfit sacrifices.

Jastrow

Jastrow

Jastrow