Reference for Chullin 231:28

עוף איכא בינייהו ר' עקיבא סבר

Or, you may Say, the difference between them is as regards fowls: R'Akiba maintains that wild animals and fowls are not included In the prohibition of the Torah but are prohibited Rabbinically, whereas R'Jose the Galilean maintains that fowls are not even prohibited by the Rabbis.

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