Is sadaqah obligatory on birds raised at home and prepared for sale when their number increases with the aim of changing the species?

If you are referring to the obligatory charity (Zakat), there is no Zakat on birds unless they are trade goods, in which case they are subject to Zakat on trade goods. The price of these birds is not subject to Zakat unless it reaches the نصاب (threshold) by itself, or by combining with other money or trade goods, and a full year has passed.