I just looked out the window to see something strange. The small birds had deserted the feeders. The only stragglers were a Red-bellied Woodpecker, two Downies, and a Red-breasted Nuthatch. All of them, even the irrepressible Nuthatch, were pressed close against branches and rigidly still. Only their eyes moved.
After several minutes two chickadees flew in calling, and the silence broke. The usual throng flowed in and around, and the silent watchers vied for suet.
I think there must have been an accipiter somewhere just out of my sight, and when it took off the chickadees issued the ‘all clear’.