Sponsored by the
Museum of Natural
Science, Louisiana State University
Date:
Fri, 20 Apr 2001 09:40:42 -0700
From: Sievert Rohwer <rohwerU.WASHINGTON.EDU>
Reply-To: Bulletin Board for Bird Collections and Curators
<AVECOL-Llistserv.lsu.edu>
To: AVECOL-Llistserv.lsu.edu
Ned's
great real data on the impact of bird-eating hawks prompts me to post the
handout I give to the Audubon groups that like to visit our collection. We take
every opportunity to try to educate people about the minimal impacts of
collecting AND about the huge effects of other species (like cowbirds and
accipiters) that are increasing as a consequence of human activities. However,
I think our case for continued general collecting will no be very compelling
until we can offer more studies similar to the DDT story.
My bet is
that changes in age ratios through time or other such analyses that enable us
to look at how major environmental changes have affected demography through
history will mean a lot to the conservation community. For example, we could
address whether the huge increase in nest loss because of the increase in meso
predators and cowbirds, has or has not affected songbird demographics across eastern
NA by looking at age rations in spring- and summer-collected specimens taken
over the past 150 years.
You are
all welcome to modify and use any of this handout in ways that may help support
collecting.
Sievert
++++++++++++++++++++
Questions You Should Ask About Collecting
Why
preserve bird specimens?
Specimens
help teach the biology and identification of birds and they serve the discovery
new knowledge. Wise conservation is built upon knowledge, so knowledge gained
from specimens can save species and populations. From field guides to high-tech
biomonitoring, museum collections provide an ongoing record of natural
populations as they change through time via natural and unnatural causes.
An
Example:
You
probably know that egg shell thinning caused by organochlorine pesticides
produced population crashes of raptors and pelicans in many parts of the world.
Most people do not realize, however, that the causal link between pesticide
residues and egg shell thinning was established by measuring historical specimens.
DDT was first used to control insects at different times in different parts of
the world. Through measurements of old and new specimens egg shell thinning in different
parts of the world was shown to be correlated with the first use of DDT in these
regions. Without a century of collecting Peregrine and Osprey egg sets
throughout Europe, these and other raptors might have been lost before we
understood and corrected the cause of their decline.
Why so many specimens?
Birds
vary by season, sex, age, and place of origin; many species wear two or three
plumages each year and many also feature several years of delayed plumage
maturity. For studies of molt and migration, collections are often sorted into
sex classes, age classes, bi-weekly time periods, and major geographic regions.
When studies of a single species requires such sampling, even the pooled resources
of every museum collection in North America often fail to generate samples of
5-10 specimens in all of the required categories. In studies of molt-migration
cycles conducted at the Burke Museum, we have found severe shortages of such
common North American birds as Arctic Terns, Indigo, Lazuli and Painted
Buntings, Bullock's Orioles and Warbling Vireos from certain seasons and
geographic regions. Without specimens in each of these varied categories, our
knowledge of the natural history and plumage cycles of even common North American
birds will necessarily remain incomplete.
Why should collecting continue?
Organisms
change through time. Birds are continuing to evolve, and the rate of evolution
is surely increasing in many species because of human-caused environmental
changes. Organisms also change due to environmental contamination, as we saw
for egg shell thinning and DDT. Published reports occasionally provide critical
data on the status of past populations, but historical specimens constitute the
sole source of new data on past generations. Specimens are proving increasingly
valuable to studies of environmental monitoring. For example the use of heavy
isotope analyses is beginning to make it possible to compare isotope ratios in
old and new seabird specimens to investigate the affects of commercial fishing
on marine communities. Such studies may reveal the causes of long term changes in
seabird populations.
Science
also changes. The molecular revolution in genetics has rendered collections of
frozen tissues of enormous value to research. Yet most of the world's birds are
not represented by even a single specimen in the world's tissue collections.
Extended wings are enormously valuable to the illustration of field guides and
to studies of molt and of flight. Yet major collections of extended wings have
begun to be developed only during the past 20 years.
What is
the impact of collecting?
Collectors
take individuals which healthy populations easily replace. By contrast,
development reduces habitat and produces permanent population losses.
Human-caused
mortality is estimated to total 200,000,000 individual birds annually in the
continental United Stated alone. Human-related mortality of birds is often
dramatic:
* British
house cats kill 60,000,000 birds and small mammals each year.
* U.S.
hunters shoot 35,000,000 Bobwhite Quail and 40,000,000 Mourning Doves each
year.
* At
least 60,000,000 birds are killed by cars in the U.S. each year.
* At
least 35,000,000 birds are killed in the U.S. each year by flying into picture
windows.
Modern
collecting for all of the natural history museums in North America accounts for
no more than 15,000 bird specimens taken from all regions of the world per
year. This is a meaninglessly small fraction of human-caused avian mortality.
Furthermore, these specimens serve education and research, and ultimately
conservation, and they are taken by scientists and students who are extraordinarily
dedicated to conservation. Rather than lobby against the scientific collecting
of birds, birders who support conservation, research and education, should
rally behind the contributions of museums and the collectors that work for
them. There is no such thing as a collector who likes killing birds. Rather
collectors respect the knowledge
generated
through specimens enough to endure the killing that is required to create
collections that will serve generations of future biologists and natural historians.
What's
the impact in hawk-equivalents?
Another
way to put the impact of collecting into perspective is to compute its effects
in hawk equivalents. The 15,000 new specimens currently being added per year to
North American collections come from throughout the world. Most regions of the
world have medium sized bird hawks, similar to the Cooper's Hawk of North
America. Bird eating hawks must consume about 25% of their own body mass in food
each day, and reproductive adults take far more prey when they are feeding
young. The average Cooper's Hawk weighs about 400 grams (females are about 500
g and males about 300g). Thus an average Cooper's Hawk consumes about 100g of
birds a day.
In most
collections the average bird specimen would be a medium sized passerine,
weighing about 30g, of which our hawk would consume 3 per day. At that rate
over 1000 individual birds are consumed per year by every Cooper's
hawk-equivalent in the world. Thus, in hawk-equivalents, the impact of
scientific collecting by North American museums has the effect of increasing
the world's population of medium-sized bird hawks by just 15 birds.
--
Sievert Rohwer
Burke Museum
University of Washington