Yesterday morning, one of the smoke detectors started its low battery chirp. I took it down, but couldn’t figure out how to remove the battery. I didn’t think Jack would think it was a sufficient emergency for me to wake him up before he would normally wake up. I put it in the mudroom, where I wouldn’t hear it chirp, since the mudroom is on the other side of an exterior door. When Jack got up, I asked him to remove the battery and it stopped chirping.
Later, when I went out to feed horses, I was astonished to hear the chirp again: same pitch, but at a more rapid interval. I was finally able to track the source of the sound: a magpie sitting on a telephone wire. It must have heard the smoke alarm chirping in the mudroom, through the dog door, and decided to incorporated the sound in its repertory.