Chullin 17 - They Should Always Do Shechitah
One of the rules of kosher slaughter of animals is formulated thus: "All are slaughtered, and we always slaughter, and we slaughter with anything, except with a harvesting sickle, a saw, animal teeth or a nail, because these instruments strangle rather than cut." What do these words mean? "All are slaughtered" teaches that birds, too, require shechitah.
"We always slaughter" according to Rabbi Ishmael, means this. In the desert, the Jews were not allowed to eat meat for pleasure, but only if brought as a peace offering. When they entered the Land of Israel, the Torah allowed them to eat meat whenever they wanted, even if not brought as a sacrifice. You might think that in exile the meat is again prohibited - so the rule teaches that it remains allowed. According to Rabbi Akiva, meat eaten for pleasure was always permitted, but the shechitah in the desert was not required. In Israel shechitah became obligatory. You might think that in exile the shechitah requirement is again not applicable, just like in the desert beforehand, so the rule teaches you otherwise - that now the shechitah is always needed.
Art: Jozef Chelmonski - Dawn. The Kingdom of Birds