A Strange Trill

     It has been snowing and sleeting for three days. The snow really came down yesterday and today. We have about 4 inches of snow on the ground. Activity in this miniberg has come almost to a stop. When I've had the dogs out our tracks are plainly visible in the snow. This morning I saw one set of tracks (not ours) in the front sidewalk. I knew who it was because the lady who made those tracks was on her way to the post office accompanied by her dog "Lucky". There were no other tracks in the snow anyplace around my house. My dogs and I cut through fresh, undesturbed, snow all around the house. Last night, about 8 pm, I was taking care of some plants in our upstairs bathroom which is located in the rear of the house. I could distinctly hear a trilling whistle. I have only known two people in my lifetime that could whistle a trill. Both belonged to a time in the past and many miles away. I could not determine the direction of the sound which lasted less than 30 seconds. My wife was downstairs completing an oil painting for a client and both dogs, she told me, were in the kitchen with her. The TV was not on; but even if it had been, it would have had to be full blast to be heard upstairs. The sound was so characteristic, a trill is the only way I can discribe it. It raised and lowered a couple of times, kind of like it was part of some sort of melody, but was neither loud enough or long enough for me to get a fix on it. Seems strange to me. But the explaination escapes me.