A swirling flock of starlings above a San Rafael parking lot has become one of the North Bay's most talked-about wildlife shows, drawing birdwatchers, families and organized viewing parties from around the region.

The display was first noticed by Neptune Bangdel, a resident of the Marinwood neighborhood, who was driving home from Point Reyes last weekend when she spotted a dark flash moving across the evening sky. She pulled over on a dead-end street near Highway 101 and watched the birds alone for about 15 minutes until they vanished. Word spread quickly, and the crowds have grown with each passing day.

A murmuration is a gathering of hundreds or thousands of starlings that fly together in wave-like patterns. Scientists do not fully understand the behavior, but it usually occurs during the cold winter months, likely for warmth and protection. A hawk will sometimes dive at the flock, opening a large hole in the formation.

Murmurations are fairly common in parts of England and elsewhere in the world, but seeing one in the Bay Area takes luck. Some evenings the birds move as one enormous group. On others they split into smaller clusters, and on some days they do not perform at all. After a week or so, the murmuration typically disappears.

On Friday, first-time visitors worried that misty, gray skies might have driven the starlings away for the season. At 5:06 p.m., however, a huge circle of flying birds drifted slowly overhead. Within seconds it split in two, then split again, and the groups headed in different directions over the nearby hills, forming shapes and waves for the next twenty minutes. The scene resembled something from the Spielberg film "Close Encounters."

"Friday night was the best display yet!" said Sara Frack, a nearby Lucas Valley resident who posted directions to the site on Nextdoor and has watched the flock grow daily.

Bangdel had seen a San Rafael murmuration two years earlier, when the starlings performed above a cemetery near the Northgate Mall, a few minutes to the south. Neighbors say the Marin flock has been large enough to notice for at least three years, and possibly longer.

This year, the birds are gathering above the open-air parking lot of Kaiser Permanente just off the Lucas Valley exit from Highway 101, which conveniently offers plenty of room for spectators to park. The show begins around 5 p.m. and lasts roughly 15 to 20 minutes.

Frack suggested staying after the performance and walking along the side of, or behind, the parking structure across the street, where the starlings settle into trees for the night. "It sounds like a roaring river, but it's actually the sound of thousands of birds," she said, adding that visitors should think twice before walking under the trees because of the droppings.

The site is about 20 minutes north of San Francisco, at the Lucas Valley/Smith Ranch Road exit from Highway 101. The address to use for navigation is 1650 Los Gamos Dr., San Rafael. Viewers are advised to arrive by 5 p.m.