This
superstition comes from the counting rhyme about magpies (and sometimes crows), which indicates that to see a single magpie is bad luck. Greeting the magpie is thought to ward off the ill
omen.
It may be significant that the
collective noun for magpies is "A tidings"
There are several versions of the
rhyme, with some similarities and differences. The only universal is that a magpie alone is always the
harbinger of
misfortune. Some examples are:
One for
sorrow, two for
mirth,
Three for a
wedding, four for a
birth,
Five for silver, six for gold,
Seven for a secret not to be told.
Eight for
heaven, nine for
hell,
And ten for the devil's own sel'.
The Folklore of Birds, by Laura C. Martin, 1993
One for sorrow, two for
joy,
Three for a girl,four for a boy,
Five for silver, six for gold,
Seven for a
secret, never to be told,
Eight's a
wish, and nine's a
kiss,
And ten for a bird you must not miss
Rhyme used for Children's TV programme, "Magpie"
One for sorrow, two for mirth,
Three for a wedding,four for birth,
five for
rich, six for
poor,
Seven for a witch, I can tell you no more.
The Dictionary of Superstitions, Oxford University Press, 1992
One for sadness, two for mirth;
Three for marriage, four for birth;
Five for
laughing, six for
crying:
Seven for
sickness, eight for dying;
Nine for silver, ten for gold;
Eleven a secret that will never be told.
Unknown source