Freeze behaviour in Common Redpoll
Carduelis flammea at a feeder
While watching an aggregation of birds at our feeders, including House Sparrow Passer domesticus, American Goldfinch Carduelis tristis, Common Redpoll C. flammea, Dark-eyed Junco Junco hyemalis and Mourning Dove Zenaida macroura, we watched all of the birds, except for two redpolls, explode into the air. We have been observing a Sharp-shinned Hawk Accipiter striatus in our neighbourhood and we suspected that its presence was the cause for the rapid exit of the passerines. Quickly this was confirmed as we witnessed the hawk flying over our fence at high speed. What the outcome of the chase might be we have no way of knowing.
The two Common Redpolls that stayed at their perches on a finch feeder froze immediately. They literally did not move at all and remained that way for several minutes. As soon as they felt it was safe to move they flew away from the feeder not even staying to get a few more seeds.
Common Redpoll "frozen" at feeder
This strategy obviously worked because the hawk took off after the fleeing birds and seemed not to notice the two redpolls which would have been sitting targets. Based on this observation one would conclude that freezing by Common Redpolls is a successful defence against predation by an accipiter.