Today we had a group of American goldfinches, an indigo bunting, and a rose-breasted grosbeak on the feeders, and a squirrel and a mourning dove on the ground, and they were all completely frozen. None of them moved for two or three minutes. I'm assuming they saw a predator, but don't these birds usually scatter at any sign of danger? They all eventually left and no birds have come to the feeder since (it's been about half an hour). Has anyone seen anything like this? It was certainly a weird experience!