[CT Birds] predation

[northernrail at comcast.net]

from John Ogren
   On Dec. 22, I found a 1st winter Northern Shrike at Otter Cove ( unfortunately 1 day before our count week-he never showed up again).  We observed the bird for about 45 minutes. During this time he was being mobbed at times by 1 or more Blue Jays. It occurred to me that these Blue Jays, tho migratory, very well may have never been exposed to a Northern Shrike before.
Later I asked Noble Proctor, while looking for this bird during our count, what would trigger this response. His answer was that  possibly birds have an inate mob reponse to such factors as the shape of a predater's hooked bill. 
John Ogren