Is a single "Basmalah" sufficient when slaughtering thousands of chickens, or is it obligatory to pronounce the "Tasmiyah" over each chicken individually?

The difference is that shooting and throwing are considered a single act of slaughter (dhaka) and require only one naming (tasmiya), even if they lead to the taking of two lives, similar to placing a knife on the throats of two sheep and drawing it across them in one motion; this is because the action is singular. As for slaughtering (dhabh), the action renews with each animal, making it permissible to consider renewing the naming, just as if there were a time interval between the two slaughtered animals.