It seems that I never answered a couple of October Mysteries.

Mystery One:

What bird built (and abandoned) this nest? 

Know where I took the photo?

This is a Common raven nest -- I photographed it at State Line Hawk Watch. (Karl Soehnlein ID'd it for me. Thanks, Karl!)

Mystery Two:

A fellow Bergen County bird lover wrote:

Can you explain why the sparrows in my yard are going into my birdhouses?

There are usually two of them, one enters the birdhouse and stays for up to one minute and then they both fly away.

I see this activity during the spring mating season, but now it’s mid-October ....

I said I had a theory, based on Eastern Bluebird behavior. What do you think?

My theory is that the sparrows are house-hunting for next spring, but Carol Flanagan wrote: