In English folklore, a spectral night-flight of seven birds whose eerie song is considered a harbinger of death and disaster. In some eschatological variations, the birds are counted as six in number, flying in perpetual search of their seventh. It is believed that when the seventh bird is found and joins their flight, the world will end.
As English folklorist Jabez Allies wrote in 1846:
"I have been informed by Mr. John Pressdee of Worcester, that the country people used to talk a good deal about the 'Seven Whistlers' when he was a boy, and that he frequently heard his late grandfather, John Pressdee, who lived at Cuckold's Knoll, in Suckley, say that he oftentimes, at night, when he happened to be upon the hill by his house, heard six out of the 'Seven Whistlers' pass over his head, but that no more than six of them were ever heard by him, or by any one else to whistle at one time, and that should the seven whistle together the world would be at an end."
The less superstitious are inclined to simply identify the seven as flights of curlews, plovers, or other birds with a distinctive whistling call. Nevertheless, as William Henderson documented in his Folklore of the Northern Counties, knowing the cause to be natural rather than is not always a shield against concern. Henderson quotes a Folkstone fisherman:
'I heard 'em one dark night last winter,' said an old Folkestone fisherman. 'They come over our heads all of a sudden, singing "ewe, ewe," and the men in the boat wanted to go back. It came on to rain and blow soon afterwards, and was an awful night, Sir; and sure enough before morning a boat was upset, and seven poor fellows drowned. I know what makes the noise, Sir; it's them long-billed curlews, but I never likes to hear them.'
Compared to kindred psychopomps and portents, the seven whistlers are almost never found in literary reference, mythemes, or folkloric signifiers outside of these scant mentions - although they do make appearances in the work of William Wordsworth and Iron Maiden.
From Iron Maiden's The Prophecy
Your life or death on me depends
Suffering and pain, impending disaster
Souls crying, the devil's laughter
Heard the cry of the seven whistlers
Lucifer smiles, looks on, and waits
Purgatory beckons, souls lost forever
Life after death or heaven hereafter
Heard the call of the seven whistlers again
Now Lucifer laughs, hell awaits
From Though Narrow Be That Old Man's Cares, by William Wordsworth
The poor Old Man is greater than he seems:
For he hath waking empire, wide as dreams;
An ample sovereignty of eye and ear.
Rich are his walks with supernatural cheer;
The region of his inner spirit teems
With vital sounds, and monitory gleams
Of high astonishment and pleasing fear.
He the seven birds hath seen, that never part,
Seen the SEVEN WHISTLERS in their nightly rounds...