I spotted a pair of birds I had never seen before in the park.  I knew they were swallows but I did not know what kind.  I dug up my bird book and identified them as tree swallows.  The male had a vivid blue head.  I knew the River had cliff swallows.  They are somewhat drab looking.  I thought it might be a barn swallow but that was not the case.  They came from nowhere and for a short time hovered back and forth over the fence that enclosed the basketball court and then disappeared.  I was thrilled to see a species of birds I had never seen before.