A strange sound in the night

YouTube link. 

For the past week, a most unusual sound has been emanating from the woods behind our house.  It was so monotonously repetitive, so mechanical-sounding, that I had doubts about it having a biological origin and initially suspected some equipment malfunction at a neighbor's house. 

Today a quick web search yielded the answer.  I've lived near woods for much of my life and have heard all sorts of owls, but didn't recognize this one.  Saw-whets are native to the boreal forests of Canada, but often winter further south in deciduous forests of the northern U.S.

The nocturnal call has been likened to the sound of a saw being whetted - thus the name.

(educational video here)