How many dead birds do you see during periods when avian flu isn't running rampant? Personally I see very few. I know all birds must eventually die, but the ratio of live to dead birds I see is probably in the thousands.

It's also probably the same reason you didn't see people keeling over from covid in restaurants and stores. Lots of people were dying, but the people on the verge of death were not out at stores and restaurants following their normal routine, they were either hospitalized or stuck in bed because they were so sick they were literally dying. I would imagine birds that are so sick they would just "drop dead" out of the sky are probably not expending tons of energy flying around for no reason and are huddled down and sheltered somewhere desperately trying to just survive.