Where did all my ferals go?

Last year I kinda fell in love with a feral pigeon I named Stumpy. He hung out near the cafe where I took my dog for coffee every day. I always sat outside because of the dog, and I got interested in this little guy with skanky feathers, a scar on the back of his neck, a stump for his left foot and some toes missing on the right foot.

One thing led to another and what started as giving him the crumbs from my croissant progressed to driving across the Bay Bridge to buy 50# bags of pigeon feed, feeding him from my hand and feeding all his buddies too.

Because I got nasty looks (and more) from people, and didn't want to attract a bunch of pigeons to the cafe, I found a nice spot around the corner on my way home and would feed them all there when nobody was looking.

They all used to sit on the overhead wires and wait for me to show up, and would fly down from two blocks away to greet me and my dog, and accompany me to the feeding spot.

I think last fall I was up to maybe 15-20 pigeons per feeding.

Then, one day Stumpy was just gone! And most of the others were gone too. I never really was interested in any of them but Stumpy, he was my favorite (and his feathers got really pretty after a while, with good nutrition, he looked like a different bird). There were a couple with striking markings or deformed feet whom I recognized...

....but now there are only about 6 birds who come to me, and I think they are all part of a different generation.

So what I want to know is - where did my Stumpy go? And where did all the others go? Could they have been taken by predatory birds? Do pigeons migrate? Do they die off quickly? I am simply mystified!