I used to have 8 or 10 pairs of cardinals, uncountable numbers of smaller birds of several varieties (wrens, sparrows, finches, etc), Mockingbirds, blue birds, indigo blues, blue jays and lots I didn't now what they were. A full feeder might last a day or two, suet cakes maybe two weeks. I'd open the back door and they'd all flutter off to the trees.
Lately, I have a small fraction of that. I saw one pair of cardinals a few days ago and a Mockingbird here or there. Few if any of the smaller ones. Suet cakes put out two weeks or more ago have barely been touched. Feeders are still half full.
There are a few predator birds and a stray cat or two, so I can see how some could have become snacks, but not all of them.
That mystery bird disease didn't bother them as the numbers didn't drop then, this is more recent. I haven't found any remains anywhere either.
I guess I'll save some money on seed this winter if the numbers don't pick up again.