Sponsored by the
Museum of Natural
Science, Louisiana State University
Date:
Wed, 18 Apr 2001 16:17:34 -0700
From: "Ned K. Johnson" <neddoSOCRATES.BERKELEY.EDU>
Reply-To: Bulletin Board for Bird Collections and Curators
To: AVECOL-Llistserv.lsu.edu
Subject: Useful data
Here are
some numbers I have found useful when dealing with anti-collecting:
Noel F.
R. Snyder and James W. Wiley (Sexual size dimorphism in hawks and owls of North
America, 1976, Ornith. Monogr. 20:78) state that a pair of Cooper's Hawks in
riparian habitat (in Arizona) take 600-700 "resident prey birds"
DURING A BREEDING SEASON (approx. 12% of the prey birds on their home range).
G.B.
Herron, C.A. Mortimore, and M.S. Rawlings (Nevada raptors: their biology and
management, 1985, Nevada Dept. Wildlife Biol. Bull. 8:25) estimated, from
evaluating the available preferred habitat, that approximately 700 nesting
pairs of Cooper's Hawks are present in Nevada. (Wildlife personnel there
actually found 193 nests between 1974-1983. No figures were presented for
number of active nests found during any one year.)
From
these figures one can calculate that from 420,000 to 490,000 birds are probably
taken in the breeding season in Nevada and only by Cooper's Hawks. If one finds
these estimates too greedy and therefore troubling, it is easy to be
conservative and cut both figures in half. 
This would provide an estimate of 300 X 350 = 122,500. birds taken in
Nevada every year, again only in the breeding season and only by Cooper's
Hawks.
If you
want to be really conservative and cut both figures down to 25% of original
estimates: 150 birds killed per nesting season X 175 pairs of hawks = 26,250
dead birds every year, only in the summer and only in one (large) state, but a
state with relatively little Cooper's Hawk nesting habitat overall
Ned K.
Johnson
Curator in Ornithology &
Professor of Integrative Biology
Museum of Vertebrate Zoology
3101 Valley Life Sciences Building
University of California
Berkeley, CA 94720-3160
USA