Is Zakat obligatory on adult pigeons kept for trade, or is the Zakat on the sold squabs sufficient, and is it permissible to pay Zakat on the day of sale or after the completion of the Hawl (one year)?

The majority of scholars stipulate for the obligation of zakat on trade goods that the good must have been acquired through an act of possession, whereas the Shafi'is stipulate that it must have been acquired through a contract of exchange. Accordingly, if the mother animals (the اصل - original stock) are not intended for trade, then their offspring are not considered trade goods and no zakat is due on them, unless they are sold and their price reaches the nisab, in which case zakat is paid on them after a year has passed from the time they came into your possession. However, if the mother animals are for trade, then the sounder opinion is that their offspring are considered trade goods.