Hum, I don't think so. Even with a few birds dying, as long as they are replenished routinely bird feeders are definitely good for winter survivorship in birds.

Birds that evolved in Central Europe don't die by winter if they can find a constant supply of food. Can choose to do a shorter migration and overwinter in northern areas and this is good for the survival of young birds. Urban areas are warmer also. Migrating south is hazardous and exhausting and there are some places in the Mediterranean or Africa that are notoriously dangerous for birds when they are hunted massively.