The bald eagle is a symbol in the United States of strength and freedom, but what is its strength in terms of population? The 2004 National Midwinter Bald Eagle Survey, sponsored by the U.S. Geological Survey (USGS), provides important information in addressing this question.
The annual survey provides a framework for assessing long-term population trends. It will take place this year from January 1-15 under the coordination of USGS scientist Karen Steenhof. January 9 and 10 are when most counts should occur.
“Each year across the United States, more than 1000 participants survey about 700 routes in 42 states,” said Steenhof. “Most participants are employees of state or federal conservation agencies, but private volunteers also help out. Sizes of survey routes vary from single fixed points to transects up to 150 miles long.”
The midwinter survey provides a unique source of long-term baseline data. Unlike bald eagle nesting surveys, it provides information about both breeding and nonbreeding segments of the population at a potentially limiting time of year. It also provides an opportunity to monitor modifications or threats to habitat at important wintering areas.
Analyses of results from past surveys by Steenhof and collaborators indicate that the number of eagles counted increased 1.9 percent each year from 1986-2000 on 563 survey routes in 42 states. These results are published in a 2002 volume of the science journal, Bird Populations.
The raw data used to calculate these trends now are available on an interactive web site: http://ocid.nacse.org/qml/nbii/eagles/. The web site allows users to view or download raw or summary data about bald eagle counts from specific survey routes or groups of survey routes. According to Sally Haerer, the Associate Director of the Northwest Alliance for Computational Science and Engineering at Oregon State University, “We worked diligently with Karen as we developed the web site, facilitated by an easy-to-use interface, which provides access to commonly requested information. Web users can search for information of interest by route name, drainage name, state, or geographic coordinates. They can retrieve count information by age classes and summary trends, and they can acquire low, high, and average counts on each survey route. Information retrieval is also easily available regarding the location of each survey, how the survey was conducted, and weather conditions during surveys.”
Says Steenhof, “After the 2005 count, we hope to do a 20-year analysis of population trends and to publish the associated raw data for the 2001-2005 surveys.”
If people want to volunteer, they can contact the state coordinators listed on the web site (follow link to forms and instructions for upcoming survey), although at this time state coordinators should have most of their volunteers lined up for 2004.
Steenhof is a research biologist with the Snake River Field Station of the USGS Forest and Rangeland Ecosystem Science Center. She works in Boise, Idaho.
The National Biological Information Infrastructure, a broad, collaborative program to provide increased access to data and information on the nation's biological resources, provided funding to make the information available on the web.
The USGS serves the nation by providing reliable scientific information to describe and understand the Earth; minimize the loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect the quality of our life.
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