The other morning I was sitting on my couch when I heard a bird singing. I started listening to it and it seemed like it was chirping at timed intervals. So I started counting. I got through 4 before it did it again. It ended at 4 and I counted a full 4 before it started at 1. Perfect rhythm. It continued this pattern for a while, then one of us got off track(I swear it was the bird!) and my counts weren't in sync with it any more. Is this a common behavior of birds?