There are some items that were created on the first day that are [susceptible to] tumah, [that which was created] on the second [day] is not [susceptible to] tumah, [that which was created] on the third [day] is [susceptible to] tumah, [that which was created] on the fourth and fifth [days] are not [susceptible to] tumah, with the exception of [a utensil made from] the wing of an oz and a plated na’amis egg. R’ Yochanan ben Nuri said: What is the difference between the wing of an oz and the wings of all [other birds]? Everything that was created on the sixth day is tamei.