Magpie Rhyme Superstition?

It's how many magpies are in view at any one time. You can't add two single magpies from two different periods of time to make joy. If you see a single magpie, that equates to sorrow. If there's a pair of magpies in view, then that's joy. You can counteract the badness of seeing a single magpie by saluting it and saying hello.