The aucuba japonica berries are ripening now. It seems odd for that to be happening in midwinter, but no doubt there's a reason. The blackbirds often pick these off, wait a moment while they appear to think better of eating them, and then throw them down. Either the berries are too big for them to swallow, or perhaps they decide that they're inedible, not that they're deterred from trying again. Perhaps that's the way evolution has fallen out in this case - get the birds to carry the seeds a little way off and then discard them. Otherwise, the berries stay on the plant for months and eventually gather below it. According to the RHS the time to plant these seeds is autumn, so maybe they need to endure the heat of summer to develop to the point of germination.