Hmmmm....Simon says the bird analogy fails because the birds could cause the grass to green and Pete says the bird analogy fails because the birds cannot cause the grass to green. You've both missed or are ignoring the point here, which is that a correlation is a correlation is a correlation. A correlation does not prove causation.

When the NFL wins, the stock market goes up. Is there a cause or is it merely a correlation? A correlation can be unrelated coicidence. To assume causation from a correlation is the fallacy. The fact that there is no causation between the birds and the grass greening does not negate the fact that there is a high positive correlation. Both increase together. Neither one causes the other. Which is the whole point. A correlation does not prove causation.

HTH,