The Liver Birds flap their wings ?

I have heard often enough the legend that, whenever a truly pure and virtuous lady passes the Liver Building, the great Liver Birds flap their wings.

As the Song of the Liver Birds says;
"Our Liverpool Ladies will hug and kiss men,
but a true virgin lady you'll find now and then.
We know who is who from our perch up on high,
and we flap our great wings any time one goes by."
Chorus; "Liver Birds are the best, tralala..."

Or; "Virgine perambulante, alas agitavero"
but I doubt that this story goes back to Roman times.

Seriously; anyone got a year for the earliest time anyone heard this?

Gerry Jones.

I heard as a kid that if the liverbirds on the Liver building ever flew away, that Liverpool would sink lol.

my grandad used 2 tell me when i was a kid that if the liver bids fly liverpool will sink an i dont get why he used 2 say it but its always stuck in my head.