Date: Fri, 20 Apr 2001 09:40:42 -0700
From: Sievert Rohwer <rohwer@U.WASHINGTON.EDU>
Reply-To: Bulletin Board for Bird Collections and Curators
<AVECOL-L@listserv.lsu.edu>
To: AVECOL-L@listserv.lsu.edu
Subject: A HANDOUT

Avecol:

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 3 per day would be consumed
by our hawk. 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
Seattle, WA 98195-3010
Voice: 206-543-4066
FAX: 206-685-3039