Trees full of northern rough-winged swallows

Northern rough-winged swallow, Charles River Peninsula, Needham, MA

 For the last two weeks the swallow population in the trees and on the high voltage wires at Charles River Peninsula has been growing and growing. Now there is easily a hundred, probably more.

Northern rough-winged swallows, Charles River Peninsula, Needham, MA

 They gather perched most of the time but occasionally burst into the air all at once.

Northern rough-winged swallows, Charles River Peninsula, Needham, MA

 The swallows in the tree branches sit and preen. Sometimes a couple will take off in chase.

Northern rough-winged swallows, Charles River Peninsula, Needham, MA

So many swallows.

Northern rough-winged swallows, Charles River Peninsula, Needham, MA

Note: I've been hesitant to identify these birds because both rough-winged and juvenile tree swallows are brown. I've also seen large gatherings of tree swallows at the CRP during this time of year. But I've finally decided to call these northern rough-winged based on the patterns of brown and white on their plumage and the fact that I haven't seen a single bird in this group that could be called an adult tree swallow.