I should comment that I have now watched the PETA video. The intro frame is a standard mechanism for releasing pigeons during a race.

It is true that some pigeons do not make it home. That's not to say that they have died, but perhaps got lost or "mysteriously" disappeared as in the article of this thread.

I agree that it large portions of pigeons were dying with each race that it would be terrible, but in practice this is often not the case.

Likewise, if pigeons fly home wounded their owners often stitch them up and care for them. If the wound is too much, then they can be unfortunately killed to remove the pain.

Compare this with feral pigeons ... The difference in "lifestyle" between them is stark.