This is the kind of reporting that winds me up – I’m sure there is probably some good science behind it, but this isn’t it.
OK, so we see the birds (rooks – crows are pretty intelligent) raising the water level to reach their morsel of food by displacing the water with stones, selecting the larger stones to do it. But just look at the archive link to tool-using rooks – these birds have simpy been trained to drop rocks on white targets to receive rewards of food. There is no “thought” of displacement as a means to raise floating objects. There is no “innovation” in their thinking – they simply repeat the learned behaviour at the first attempt when presented with the new situation – the very opposite of innovation. Jeez.