Distinguishing Bird Conservation Lists, Trends and Risk Categories
How to tell a population trend, a conservation priority list and an IUCN extinction-risk category apart, and read each label by its system, date and geography.
Contents
- The three record types at a glance
- Population trends measure change, not risk
- Priority lists: Birds of Conservation Concern 2021
- Extinction-risk categories: the IUCN Red List
- Regional Red List assessments can differ from global ones
- Keep legal status in its own column
- How to read a conservation label
- Illustrative example
Conservation labels can look alike, but they answer different questions. A population trend asks whether a group of birds is becoming more or less abundant. A conservation priority list asks which birds an agency should focus attention on. An extinction-risk category asks how likely a species is to disappear from the wild. Legal protection is a fourth thing again. If you watch birds on Montana's northeastern prairies and wetlands, such as around Medicine Lake, you may see one species described in all of these ways. To read any label correctly, identify which kind of record it is, who issued it, when it was assessed, and what geography and population it covers. Do not treat it as interchangeable with any other label.
The three record types at a glance
| Record type | Question it answers | Example | What it does not tell you |
| Abundance trend | Are numbers rising or falling over a stated period and region? | CAFF's 2015 Arctic Migratory Birds Index | Extinction risk, conservation priority or legal status |
| Conservation priority list | Which birds deserve agency attention beyond those already legally listed? | U.S. Fish and Wildlife Service Birds of Conservation Concern 2021 | Whether a species should be legally listed, or a global risk category |
| Extinction-risk category | How likely is the taxon to go extinct in the wild, judged against set criteria? | IUCN Red List categories, applied globally or regionally | Legal status in any country or state, or a regional trend on its own |
Population trends measure change, not risk
A trend index tracks how abundance changes over time for a defined set of birds. The Conservation of Arctic Flora and Fauna (CAFF) 2015 Arctic Migratory Birds Index is a regional assessment of abundance changes in selected Arctic-breeding birds. Because these birds migrate along flyways, it uses information from both inside and outside the Arctic to support flyway conservation. This matters for prairie observers. A migrant stopping at a northern Great Plains wetland may belong to a population whose trend is measured for its breeding region, not for the place where you see it.
An abundance trend is a different measurement from global extinction risk. A falling index is a meaningful signal. However, it does not convert into a Red List category, and a stable index does not make a species safe. When you note a trend, also record its time period, the region it covers and the set of species it uses.
Priority lists: Birds of Conservation Concern 2021
Birds of Conservation Concern 2021 is a U.S. Fish and Wildlife Service report. It names 269 taxa as conservation priorities beyond those already federally listed as threatened or endangered. To select them, the agency considered abundance, population trends, threats, and both breeding and nonbreeding ranges. It made these assessments at several scales: continental, island, and terrestrial or marine bird conservation regions.
Two points shape how you should read this list. First, it is a priority-setting tool. It makes no finding about whether a species warrants consideration for listing under the Endangered Species Act. Second, its findings are dated to the 2021 report. A bird can appear on the list for one conservation region and not for another, so check which scale the listing applies to before you describe a species as a bird of conservation concern.
Extinction-risk categories: the IUCN Red List
The IUCN Red List assigns taxa to categories of extinction risk using a fixed system, currently Categories and Criteria Version 3.1. The second edition of Version 3.1 keeps the same assessment system as the first edition, so a category assigned under either edition rests on the same definitions.
- Extinct (EX): the last individual has died.
- Extinct in the Wild (EW): survives only in captivity or cultivation, or as a naturalized population outside its former range.
- Critically Endangered (CR): extremely high risk of extinction in the wild.
- Endangered (EN): very high risk of extinction in the wild.
- Vulnerable (VU): high risk of extinction in the wild.
- Near Threatened (NT): close to the thresholds for a threatened category.
- Least Concern (LC): does not meet the criteria for a threatened category or for Near Threatened.
- Data Deficient (DD): not enough information to assess risk.
- Not Evaluated (NE): not yet assessed.
Only CR, EN and VU count as 'threatened.' Data Deficient and Not Evaluated are not low-risk labels. They mean the risk is unknown or has not been assessed.
The threatened categories are based on five criteria. Criterion A covers population reduction. B covers geographic range. C covers small, declining populations. D covers very small or very restricted populations. E covers a quantitative analysis of extinction probability. A taxon qualifies for a category if it meets any one criterion, but assessors must consider all of them. A Red List entry will often cite a code such as a criterion letter. That code tells you which kind of evidence drove the category.
Regional Red List assessments can differ from global ones
IUCN's regional guidelines (Version 4.0, 2012) adapt the Red List for a country, state or other region. Assessors first decide which populations are eligible. They then make an initial regional assessment and adjust it after considering populations outside the region. One factor is the 'rescue effect,' where birds immigrating from elsewhere can prop up a regional population. Two extra categories apply. Regionally Extinct (RE) means the taxon is gone from the region. Not Applicable (NA) means the taxon is not eligible for regional assessment.
Because of these steps, a bird's regional category can legitimately differ from its global one, in either direction. A category can also change when new information arrives or when taxonomy is revised, not only when the bird's actual risk changes. Before you conclude that a species has declined, check the stated reason for any change in category.
Keep legal status in its own column
Federal threatened or endangered status under the Endangered Species Act is a legal designation. It is not a Red List category, and it is not a Birds of Conservation Concern listing. The 2021 priority list deliberately excludes species that are already federally listed, and it does not decide whether a species should be listed. IUCN categories carry no legal force on their own. Any state designation, including one in Montana, comes from that state's own process. Record it separately, citing the issuing authority and the date.
How to read a conservation label
- 1. Identify what the record does. Does it measure change in abundance, assign conservation priority or assess extinction risk?
- 2. Read its scope. Note whether it covers the globe, a continent, a conservation region or a state, and which taxon or population it covers, such as the breeding population or birds passing through.
- 3. Check the date and the stated rationale. For a trend, that is the period measured. For the Red List, it is the qualifying criteria. For a priority list, it is the report year and scale.
- 4. Before you record a current category, consult the issuing authority's latest species assessment. The figures in a report reflect the year it was published.
- 5. Enter any legal designation separately, with its own source and date.
If you keep a checklist, notebook or interpretive sheet, give each species entry these fields: taxon and population; exact label; issuer; assessment system and version; assessment and publication dates; geography; breeding or visiting population; the measured trend and its period, or the qualifying criteria; the rationale; and a separate legal-status reference. Compare two records only after these fields match. For example, do not compare a global category with a regional one as if they were the same kind of finding.
Illustrative example
Consider a fictional prairie bird with a declining regional abundance index and a global Least Concern assessment. Both entries can be accurate at the same time, because they measure different things over different scopes. Keep both, each with its own date, geography and basis. The declining trend does not give you a new global category, and neither record establishes a Montana legal designation. To find out whether the trend has prompted a regional risk assessment or a place on a priority list, look for that assessment directly rather than inferring it.
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