It鈥檚 September and that means everyday are putting on their near the mouth of the 黑料新闻 River.
Hundreds of thousands of the birds come from all over New England and the Canadian Maritimes to roost in the marshes just south of Essex before they head south for the winter.
These tiny native birds, with an iridescent dark blue top and white underbelly, weigh about 17 grams. Matthew Bell from the said that鈥檚 about the weight of three quarters.
Bell says it鈥檚 a good idea to use binoculars to really appreciate the show which 鈥渓ooks like TV static or spilled cracked pepper all over your counter.鈥�
Once they gather by the hundreds of thousands over the marshes, the tree swallows then quickly descend to pick an individual reed where each bird will spend the night.
"Sometimes it's a plummet where every bird disappears in 30 seconds, the sky just empties out completely, other nights, it looks like a dramatic tornado,鈥� Bell said.
He says scientists can鈥檛 say exactly why the tree swallows pick this spot every year to roost right before their migration south.
"We assume that they pick it in part, strength in numbers. Most of their predators probably can't swim out here to get them, raccoons, skunks, stuff like that,鈥� he said.
Boaters and kayakers gather in the river daily right before sunset to watch the birds arrive. and the offer boat tours to experience the event but tickets often sell out quickly.
The bird numbers peak in mid-September and disappear in late October when the swallows head south for the winter.
