There is a traditional distinction between birds and animals that runs through the common law. There is a provision specifically for roosters, for cocks, because sadly they are often very damaged in the fighting, and it is often the case that they're also fed with steroids to make them more aggressive. Quite sadly, the most humane response to seizing the birds is to put them down. That's not necessarily the case with all other animals.
Remember that animals will also be dealt with under provincial legislation. There are protections for animals under provincial law, which still abides even without this.