Information Sources for Species Assessments

Banding a Black Oystercatcher
Banding a Black Oystercatcher at Kenai Fjords National Park, AK
[Photograph: Ron Niebrugge, USGS Alaska Cooperative Research Unit]

Different sources of information are used to assess the status of a population or species. These include:

For additional information resources, visit our Maps and Data page.

Which birds do we conserve?

Northern Pintails
Northern Pintails (Anas acuta)
[Photograph: Dave Herr/USDA]

With over 700 bird species regularly occurring in North America, how do we know which ones are in trouble?

Before allocating resources to conserve a species (or subspecies), biologists must have a priority list based on some criteria for status and risks faced by each species. They start by monitoring populations, using many methods and information sources. Data from monitoring surveys, in conjunction with information gathered from a variety of other sources such as peer reviewed literature, research reports, and species expert opinions, are used to formulate species status assessments. These assessments serve as the biological basis for prioritization efforts, which may also incorporate non-biological criteria (e.g. feasibility, partnership potential, cost-effectiveness of conservation, etc.) in setting bird conservation priorities.

Species Status Assessment

A species status assessment is a process that uses defined set of criteria and rules (often quantitative) to summarize what is known biologically about species of interest in order to determine their status at a given geographic scale. The following indicators of species vulnerability represent the most commonly used criteria in bird species status assessments:

  • Population size - number of individuals in the population. It is assumed that species with small populations are more vulnerable to extinction than species with large populations.
  • Population trend - direction and magnitude of changes in population size.
  • Distribution - geographic extent (range) of a species or population during the breeding and non-breeding periods. Generally species with narrowly distributed populations are more vulnerable than species that are widely distributed.
  • Threats - external conditions that can significantly affect the ability of a population to survive or successfully reproduce. Threats may exist during the breeding, migrating, and non-breeding periods.

Based on evaluations of data and information gathered on a species from various information sources, a numerical score from a predefined ranked scale for each criterion is given to each species of interest. Use of a standardized scoring system allows for equivalent comparisons across species.

Methods and results from some of the widely used status assessments in the United States are found at:

State of the Birds

The State of the Birds reports provide comprehensive analyses of the status of bird populations in the United States.

Priority Species

Henslow's Sparrow (Ammodramus henslowii)
[Photograph: John Cassady]

Many prioritization efforts seek to halt species declines before the situation becomes expensive (i.e. a recovery effort). Here are some of the major lists of species at risk:

The NBII Program is administered by the Biological Informatics Program of the U.S. Geological Survey
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