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2010
Vol. 81 THE RAVEN
Page 5'
THE VIRGINIA BALD EAGLE SURVEY: A HISTORY
BRYAN D. WATTS
Center for Conservation Biology
College of William and Mary and Virginia Commonwealth University
Williamsburg, VA 23187-8795, USA
bdwatt@wm.edu
The Virginia Bald Eagle Survey is a national treasure.
The survey has become one of the most significant serial
data sets in the world. Over the past 55 years, the survey has
documented biocide-induced reproductive suppression,
the resulting population low, and a dramatic recovery
in both reproductive rates and the overall population
following the ban of DDT and like compounds. The survey
itself has become one of the most effective tools in the effort
to recover the eagle population in Virginia, allowing for the
enforcement of wildlife laws and providing information
on the effectiveness of management actions. More than
population information alone, the effort has produced a
wealth of ecological information on a population recovering
within an increasingly human-dominated landscape. It has
become one of the best records of arguably the greatest
conservation achievement in our nation's history. My
objective here is to provide a brief history of the survey
effort and some of the events that shaped its development.
Tyrrell Survey
In the spring of 1935, during a time when bald eagles
were persecuted throughout their range, a bill was
introduced in Congress to protect the national symbol
from extinction. The bill passed the Senate, but failed in
the House of Representatives. [A modification of this bill
became the Bald and Golden Eagle Act of 1940 (16 U.S.C.
668-668d; 54 Stat. 250).] During the breeding season of 1934,
W. Bryant Tyrrell and other members of the Natural History
Society of Maryland made regular observations of an eagle
nest along the Magothy River south of Baltimore, including
prey use and chick development through the period of
fledging. Photographs of the chicks appeared in the New
York Times and were brought to the attention of Warren F.
Eaton. Eaton was working on the status of hawks and owls
and their economic importance. Eaton contacted Tyrrell
about the possibility of a survey of eagles throughout the
Chesapeake Bay region and an investigation of food habits.
Understanding the gravity of the situation and the
need to collect information to support the Senate bill, Tyrrell
wrote a letter to Professor R. V. Truitt of the University of
Maryland inquiring about the potential for funding from
the University or the State to support such a survey. Truitt
contacted the National Audubon Society and in January
of 1936 the president of that Society, John H. Baker, met
with Warren Eaton and Bryant Tyrrell in New York City to
lay out a plan and to acquire associated funding to survey
nesting eagles throughout the Bay region, including New
Jersey, Delaware, Maryland, and Virginia.
Tyrrell initiated the nest survey in February of 1936
(Tyrrell 1936). He began by contacting the community of
ornithologists, oologists, game wardens, and other people
who were most likely to know of nest locations. Harold H.
Bailey provided him with a map of 54 nests in Virginia.
Edward J. Court, a prominent egg collector in the region,
claimed to know of 90 nest locations, but provided Tyrrell
with only eight that could not be climbed. Tyrrell used these
eight locations as a basis for the survey, but when entering
a new community he would also visit the country store and
local landowners to take advantage of local knowledge
about breeding pairs, and thus accumulated additional
nest sites for the survey.
Although the survey was ground-based and covered
only a portion of the region, it became the benchmark
against which future efforts would be compared (e.g.,
Abbott, 1963; Byrd et al., 1990; Watts et al., 2008). This is
true because it was the only major effort to quantify eagle
numbers and productivity prior to the DDT era. In Virginia,
the survey included the Potomac River to its mouth, a small
portion of the Rappahannock River, approximately 20 miles
of the James River east of Richmond, and the coastal area
from Pungo through Back Bay. Tyrrell surveyed 19 nests,
16 of which were occupied in 1936. Fifteen of these nests
successfully produced 33 chicks.
The efforts of Tyrrell have provided the conservation
community with more than a population survey. His report
to the National Audubon Society, notes, and nest logs
provide an account of eagle-human interactions during a
critical time before both
the
passage of the Bald and Golden
Eagle Act and the DDT era, a time during which eagles
were under considerable pressure from various sectors
of society (e.g., loggers gave eagles no consideration and
numerous nest trees were lost annually to forest clearing;
many fur trappers, farmers, and waterfowl hunters shot
eagles on sight; collectors staked out nests in order to take
adult pairs and eggs for sale on the open market).
Modern Survey
Despite the fact that he never surveyed eagles within
the Chesapeake Bay, Charles
L.
Broley and his work on
Florida eagles ignited a national conservation movement
and indirectly led to the establishment of the Chesapeake
Bay Bald Eagle Survey. Broley, a retired bank manager from
Winnipeg, Canada, spent the winter months in Tampa,
Florida. He became increasingly concerned about habitat
loss, shooting, and egg collecting in western Florida that
he believed was causing eagle declines. At the age of 60, he
initiated a banding program in 1939 and banded more than
1,200 eaglets over the following 20 years. Broley's seminal
work not only documented new aspects of eagle ecology
(Broley 1947), but also provided one of the most complete
records of progressive nest failures during the early years
of the DDT era. In an area where he once banded more than
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Vol. 81
THE
RAVEN
2010
150 chicks in a single year, by 1958 Broley could only locate
a single chick to band. His energy and relentless advocacy
on behalf of eagle conservation spawned efforts across the
species range. His belief that the Chesapeake Bay could
serve as a stronghold for the species in the East led to the
Bay becoming one of the first focal monitoring locations.
In 1955, a committee was established within the
Audubon Naturalist Society to collect data on the status of
bald eagles within the Chesapeake Bay region (Abbott 1957).
Jackson Miles Abbott was a member of that committee and
would lead the survey effort for the next 20 years. Abbott, a
military engineer, accomplished naturalist, artist, lecturer,
and writer transformed the effort from a volunteer project
to a formal survey. Many of the ecological discoveries
made in the survey's early years led to the development of
effective aerial monitoring. Abbott's detailed field notes and
published papers provide a complete accounting of efforts
and observations during a critical period of the survey's
development. The survey would not have survived and
prospered without his leadership and dedication.
Between 1956 and 1962, the survey progressed from
a volunteer-based ground survey to a more effective
aerial survey (Abbott 1967). The survey was first
conceived as a volunteer effort. The committee executed
an outreach campaign to recruit observers that included
announcements in the Washington Post. In the first year,
nine observers provided nest locations and observations.
Despite a considerable outreach campaign, the committee
was unable to engage a large enough pool of qualified
observers to cover known nesting sites or to complete
follow-up productivity observations. By 1960 the effort had
collected information on 68 nest sites, but information on
productivity was limited. During the first 4 years, Abbott
was never able to exceed 20% coverage of known nests
by volunteers, due to the small pool of observers and the
remoteness of many nests. During these initial five years
it became increasingly evident to Abbott that a ground
effort would not be adequate to meet survey objectives.
In the spring of 1959, Abbott had the first opportunity to
do a limited flight for eagles in an H-23 army helicopter
and realized that aerial surveys were the best option for
monitoring nests. During the 1960 National Audubon
Society convention in New York City, Alexander Sprunt
IV announced a continental effort by the Society to assess
bald eagle populations. The effort focused on a mid-winter
survey and breeding surveys within selected geographic
areas of importance. The Chesapeake Bay Survey joined
this effort, and in 1962 Abbott conducted the first aerial
survey of the Bay with an assessment of productivity
(Abbott 1963). The army provided helicopter support
along the Potomac and the United States Fish and Wildlife
Service provided survey planes for the remaining areas.
In 1963, Frederick R. Scott III joined Abbott in
conducting the aerial survey and the team flew the Bay for
eagles through 1976. Often considered the dean of Virginia
birdwatchers, Scott had an encyclopedic knowledge of
bird populations, was the editor of The Raven for 27 years,
and was one of the region's staunchest conservationists.
During most years, Abbott flew the upper Bay from the
Potomac River north and Scott flew the lower Bay from
the Rappahannock River south. Through the 1960s and
1970s, Abbott and Scott served as witnesses to a stable but
unsettled eagle population with low productivity and high
abandonment rates.
The year 1977 was a transition year for the bald
eagle survey and for eagle conservation within the
Chesapeake Bay. In January of 1977, the Chesapeake
Region Eagle Group was established with representatives
from the Fish and Wildlife Service, Maryland Wildlife
Administration, Virginia Game Commission, the National
Wildlife Federation, the Audubon Naturalist Society, the
Maryland Ornithological Society, and the Virginia Society
of Ornithology. Very close to this time period, the Fish and
Wildlife Service, under the authority of the Endangered
Species Act, appointed a Chesapeake Bay Bald Eagle
Recovery Team to develop a recovery plan and to oversee
monitoring and recovery efforts. During that same year, the
state wildlife agencies assumed responsibility
,
for the nest
survey. In Virginia, Mitchell A. Byrd, professor of biology at
the College of William and Mary and a true pioneer of bird
conservation, conducted the survey on behalf of the state
agency, and he remained committed to the survey for the
next 34 years. In 1991, Bryan D. Watts joined the Virginia
survey and the two monitored the population together for
the next 20 years.
Following the federal listing of bald eagles in 1967
under the Endangered Species Protection Act of 1966
(16 U.S.C. 668aa-668cc) and, subsequently, under The
Endangered Species Act of 1973 (16 U.S.C. 1531 et seq.),
efforts were mounted throughout the species range
and there was a movement toward more standardized
monitoring programs. The Virginia survey transitioned
to a standard two-flight approach, consisting of one flight
in March to locate new nests and determine the status of
known nests, and a second flight in late April and May
to check active nests for productivity. The survey also
became more systematic in its coverage of the Coastal Plain
including Chesapeake Bay tributaries to the fall line, the
Eastern Shore, and lower Tidewater including Back Bay and
the North Landing River. Mapping of nests became more
standardized, using 7.5 minute topographic quadrangles
to provide the resolution needed to enforce regulations of
The Endangered Species Act.
As bald eagle populations continued their remarkable
recovery throughout the late 1990s, wildlife agencies across
the species range began to divert resources away from
eagle monitoring to more pressing priorities. Beginning
in 2000, financial responsibility for the Virginia survey has
been increasingly assumed by the Center for Conservation
Biology, a research and conservation organization founded
in 1992 by Bryan Watts and Mitchell Byrd. The Center is
shared between the College of William and Mary and the
Virginia Commonwealth University and is committed to
long-term species conservation. This survey has continued
to document eagle population growth, productivity and
distribution to the present. The 2010 survey checked more
than 900 nests and monitored 684 occupied territories
(Watts and Byrd, 2010). Throughout the years, the survey
has conducted more than 22,000 nest checks, including
more than 13,000 since the year 2000.
2010
Vol. 81
THE RAVEN
Page 7
Acknowledgments
The Virginia Bald Eagle Survey has truly been a
community effort with contributions from dozens of eagle
biologists, environmental activists, bird watchers, and
concerned citizens all coming together around a common
goal. Funding for the Virginia Survey has been provided
by the Virginia Department of Game and Inland Fisheries,
U.S. Fish and Wildlife Service, U.S. Department of Defense,
Audubon Naturalist Society, National Audubon Society,
Virginia Society of Ornithology, and the Center for
Conservation Biology.
Literature Cited
Abbott, J. M. 1957. Bald Eagle survey: first annual report.
Atlantic Naturalist
12:118-119.
Abbott, J. M. 1963. Bald eagle survey for Chesapeake Bay,
1962.
Atlantic Naturalist
18:22-27.
Abbott, J. M. 1967. The Chesapeake Bay eagles: Summary
Report - 1936; 1955-1965.
Atlantic Naturalist
22:20-25.
Broley, C. L. 1947. Migration and nesting of Florida Bald
Eagles.
Wilson Bulletin
59:1-68.
Byrd, M. A., Therres, G. D, Wiemeyer, S. N., and M. Parkin.
1990. Chesapeake Bay region bald eagle recovery plan:
First revision. U.S. Department of the Interior, Fish and
Wildlife Service, Newton Corner, MA. 49 pp.
Tyrrell, W. B. 1936. Unpublished report of bald eagle
nest survey of the Chesapeake Bay region. National
Audubon Society, Washington, D.C. 30 pp.
Watts, B. D. and Byrd, M. A. 2010. Virginia bald eagle
nest and productivity survey: Year 2010 report.
Center for Conservation Biology Technical Report
Series, CCBTR-10-09. College of William and Mary,
Williamsburg, VA. 40 pp.
Watts, B. D., G. D. Therres, G. D., and Byrd, M. A. 2008.
Recovery of the Chesapeake Bay bald eagle nesting
population.
Journal of Wildlife Management
72:152-158.
