“There is a superstitious belief that swans cannot hatch their eggs unless a storm is raging, the sky mad with lightning bolts and thunderclaps. I suspect this is true, for on the countless occasions I have gone blundering into swans’ nests, I have never seen eggs hatching, and the weather has invariably been balmy, for that is the kind of weather I prefer when blundering about among the nests of swans.”

From Quite A Few Things I Know About Swans by Dobson (out of print)