York County Audubon will present The Amazing Winter Crow Roost, an online session, on Tuesday, Feb. 16.

According to Keith Eddings of The Eagle-Tribune, “The annual arrival of thousands of crows in Lawrence, Massachusetts, is a spectacular display of sight and sound, a massive swarm of as many as 20,000 crows, a sky blotted black by their numbers, a crescendo of cawing that slowly fades to an eerie silence as night closes in. As it has for at least 30 years, the flock of mostly American crows arrives in Lawrence in November, and carries out some of the primordial behaviors that still puzzle the amateur birders and professional ornithologists who study what many of them believe are the world’s most clever and social birds.”

What brings these thousands of crows – a mix of residents and seasonal migrants from as far as the St. John’s River in Canada — to places like Lawrence for the winter from November to March? Why do they stage so massively in the evenings, then fly off together in the dark to roost elsewhere, then scatter in the morning to forage for food as far as 50 miles away, then return to stage and roost for another night?

York County Audubon will host Dana Duxbury-Fox and Bob Fox at 7 p.m. Tuesday, Feb. 16. They will share a wealth of information about crows.

According to a written statement from Maine Audubon, “The couple from North Andover, Massachusetts, have birded worldwide through more than half a century, logging over 6,500 of the world’s 10,000 or so species, In 2013, Bob co-authored “The Birds of New Hampshire,” a 473-page illustrated book that chronicles all 427 species living in that state. He helped found Manomet Bird Observatory.

“Dana has spent 70-plus summers in New Hampshire, where she became fascinated by loons. She has long been active in chronicling and protecting bird life.”

For more information, visit www.wintercrowroost.com.

York County Audubon will present the program online. It’s available free of charge, but advance registration is required. To register, visit yorkcountyaudubon.org, and click on the link. After registering, participants will receive a confirmation email containing information about joining the program.