Trading (buying and selling) in sparrows

Question 5: My brother trades in sparrows; is this permissible?

Answer: Selling sparrows is permissible, as they have not been exempted from the general ruling of permissibility of selling… read more here.

Is it permissible to take oaths while buying and selling if one is truthful?

Question 1: Is it permissible to make oaths while buying and selling if one is truthful?

Answer: Making oaths in buying and selling is Makrooh (disliked) in general, whether one is truthful or not. If a person lies in his oath then it is Makrooh in the sense of being Haraam (forbidden); the sin is greater and the punishment is more severe because it is a false oath… read more here.