Kosher and Non-Kosher Fowl
The Torah lists twenty-four families of non-kosher birds which, according to modern scientific classification, include thousands of known species and sub-species. Some of the non-kosher birds listed in the Torah are the barn owl, bat, cormorant, eagle, falcon, gull, hare, hawk, hoopoe, ibis, kite, magpie, ossifrage, osprey, ostrich, owl, pelican, raven, stork, and vulture. Though it is a mammal, the Torah includes the bat in the list because it uses different criteria for classification than modern science. The word “Auf” – עוף in Hebrew, which is usually translated as fowl, actually means any flying creature.
Even though the Torah does not specify the signs by which to recognize a kosher bird, as it does with other animals, nonetheless, the rabbis gave us four general indicators by which to differentiate between kosher and non-kosher fowl. Not all kosher birds possess all four indicators and some non-kosher birds may possess one of them, therefore, they are general guidelines rather than sure signs. Two of these signs are primary indicators of the kosher status of the bird and two are secondary.
The two primary indicators are:
a) The muscular wall of the gizzard of a kosher bird may be easily peeled off by hand, whereas the gizzard of a non-kosher bird will not peel easily.
b) Non-kosher birds tend to be birds of prey that hunt for their food. Therefore, they will use their claws to capture and hold their prey as they devour it. Kosher birds do not eat in this fashion.
The secondary indicators are:
a) Kosher birds will tend to have three toes in the front and one extra toe in the back, whereas non-kosher birds may have two, three or four toes. They may have three toes in the front and one in the back, two toes in the front and two in the back or all four toes in the front.
b) Many kosher birds will possess a crop which non-kosher birds do not have. This is a pouch-like organ on the wall of the esophagus which temporarily stores undigested food before it goes to the stomach to become fully digested. Ducks and geese do not have crops. However, since they possess the other three indicators of a kosher bird they are kosher.
Since the four above indicators are not of biblical origin and it would be extremely difficult to determine the kosher status of all the thousands of bird species, therefore, generally, only birds that are known to be kosher by tradition are consumed. The most common birds that are traditionally accepted as being kosher are:
a) All members of the chicken family.
b) Domesticated ducks.
c) Domesticated geese
e) Domesticated turkeys
Geese that have been forced fed by ramming a metal funnel down their throat could lose their kosher status because this method of feeding can puncture the esophagus. This would render the goose a treifah, which, as will be explained, means that the animal has a physical condition which will cause its death.