[TN-Bird] Re: Cooper's lifting capacity
- From: "Wallace Coffey" <jwcoffey@xxxxxxxxxx>
- To: "Tennessee Birds" <tn-bird@xxxxxxxxxxxxx>
- Date: Tue, 17 Dec 2002 22:50:15 -0600
Dean Edwards' observation of an Cooper's Hawk flying off
with the Upland Sandpiper fits the formula. Thanks for that
contribution, Dean.
Ralph S. Palmer wrote in the "The Shorebirds of North America"
that the Upland Sandpiper weighs 6-7 ounces. No doubt
someone else has better information.
Robert Storer, at the University of Michigan Museum of Zoology
at Ann Arbor in 1966, caculated that 12.8 % of the body weight for
Cooper's males and 11.5 % of the body weight for females
was the amount of weight the species could lift.
That would be about 5-6 ounces if you used the weight for the
Cooper's Hawk males and females as given by Paul Johnsgard
in his book "Hawks, Eagles & Falcons of North America." To
arrive at that you would have to convert grams to ounces. At
least that is what I got if I got my math right. I ususally don't :-)
Storer published his findings in an interesting article in
THE AUK (83:423-436, July 1966) "Sexual Dimorphism and
Food Habits in Three North American Accipiters."
Storer caluclated the mean weight of 60 prey items for a male
Cooper's Hawks to be 37.6 grams and for 90 prey items for a
female to be 50.7 grams. Based on his caculations, that was
12.8 % of the body weight for males and 11.5 % of the body
weight for females.
Johnsgard cites J.B. Dunning: "Boidy weights of 686 species
of North American birds" (Western Bird Bandingt Assoc., 1984),
for the gram weight for male Cooper's as males 297-380 grams
and females as 460-588 grams. Clark and Wheeler in 1987
listed males 302-402 grams and females 479- 678 grams.
No one has given estimates for a Cooper's Hawk lifting a
house cat and carrying it off. Maybe someone will come across
a study on that :-)
Let's go birding.....
Wallace Coffey
Bristol, TN
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