I was sitting with my three chooks in the backyard yesterday afternoon. All three birds were happily browsing on the lawn. One chook made a cluck, only slightly different to an ordinary 'cluck', and all three FROZE in place. They held that position for at least three minutes. They were all gazing in the same direction. Any ideas ? I thought not a sky predator, as they always run to cover in that circumstance, they do the same with any unfamiliar noise. They remained in the open and didn't move even when I started moving about, looking for what might have caused the alarm. I live in a very suburban house, surrounded by other houses with small back yards. I would love to hear your ideas ?