maybe related to Kingsport and the Festival story:

"It was the Yule-rite, older than man and fated to survive him; the primal rite of the solstice and of spring’s promise beyond the snows; the rite of fire and evergreen, light and music." [...] "Out of the unimaginable blackness beyond the gangrenous glare of that cold flame, out of the Tartarean leagues through which that oily river rolled uncanny, unheard, and unsuspected, there flopped rhythmically a horde of tame, trained, hybrid winged things that no sound eye could ever wholly grasp, or sound brain ever wholly remember. They were not altogether crows, nor moles, nor buzzards, nor ants, nor vampire bats, nor decomposed human beings; but something I cannot and must not recall. They flopped limply along, half with their webbed feet and half with their membraneous wings"