[CT Birds] 1/21/08 Ansonia Nature Center and Selective Mobbing of Raptors

[james.bair at snet.net]

1/21/08 Chilly afternoon walk at Ansonia Nature Center:

Sharp-Shinned Hawk, BALD EAGLE (flyover), Mourning Dove, Downy Woodpecker, Blue Jay, Am. Crow, B-C Chickadee, W-B Nuthatch, N Mockingbird, N Cardinal, D-E Junco, FOX SPARROW, Swamp Sparrow, White-Throated Sparrow, House Finch, Common Grackle, House Sparrow.

The Sharp-Shinned Hawk was perched near the nature center's feeders, as Sharpies are wont to do this time of year. Three or four Chickadees were not mobbing it, but were perched about twenty feet from it calling around it as though they were announcing its presence to the other birds in the area. They continued to do this when the Sharpie flew to a different tree about fifty feet away on the other side of the feeders. They moved also and surrounded the hawk with calls. The Sharpie was small; when I first saw its silhouette, I thought it was a Kestrel. Indeed, it was about the same size as the Blue Jays at the feeder.

What struck me was that the Blue Jays were paying no attention to the little Sharpie. I have seen Jays mob or otherwise announce all kinds of "mid size" predators including cats, Red-Tails, Broad-Wings, Great Horned Owls, and other raptors. I was wondering if the Sharpie was just too little for the Blue Jays to take notice, or were the Chickadees' harassment sufficient enough for the Blue Jays (there were at least four present) not to participate? Perhaps there is a predator size limit, so a Jay will disregard a bird as small as itself? 

Jim Bair