Subject: crow mobbing (fwd)
Date: Jun 9 13:52:43 1994
From: Dan Victor - dvictor at u.washington.edu


Here's a reformatted copy. --Dan

---------- Forwarded message ----------
Date: Thu, 9 Jun 94 11:34:17 -0700
From: Dennis Paulson <dpaulson at ups.edu>
To: Multiple recipients of list <tweeters at u.washington.edu>
Subject: crow mobbing

To add to Peter Whitlock's good comments on predator mobbing, there is no
reason to consider mobbing by neighbors as "nonsense" behavior. If mobbing
serves to acquaint individuals with potential predators in the area,
neighbors should do it. If it serves to inform the predator that these
birds know of its presence and are therefore poor risks for predation
attempts, neighbors should do it. If it serves to chase the predator away
from the area, neighbors should do it. Probably most of the advantages
that accrue to the nesting pair (protecting their nestful of eggs or
young) also accrue to nearby unrelated individuals. I don't think this
happens from "time to time," I think it is the rule. Whenever I imitate
pygmy-owl calls to attract passerine birds just to see what's in the area,
the sound attracts birds from all territories within hearing distance, as
far as I can tell. The fun starts when a pygmy-owl comes in too!

An important theoretical paper on the subject (E. Curio, U. Ernst, and W.
Veith, The adaptive significance of avian mobbing I & II, Zeitschrift f=FCr
Tierpsychologie 48: 178-202, 1978) listed quite a few potential advantages
of mobbing. Some of them seemed to be rejected by available evidence, but
there were a surprising number of hypotheses that weren't rejected. A
multifunctional adaptation.

Dennis Paulson