Chimney Swifts:  Wings Alternate, or in Unison?  What do you think?

If you have visited Hook Mountain you have undoubtedly seen the Chimney Swifts fly around the Hook.  This year one of the hawk watchers suggested that these fascinating birds alternated their wings in flight.  We wondered and decided to take a video, slow it down, and see if we could determine if the Swifts use their wings alternately or in unison.  Check out the video to see!