For decades, species watchlists have helped quantify the plants and animals most at risk of extinction and inform conservation actions. The WatchList of Terrestrial and Freshwater Bird Habitats of the U.S. and Canada — the Habitats WatchList — developed by American Bird Conservancy in partnership with NatureServe and Birds of the World authors Iain Campbell and Philip Chaon, offers a new look at habitats: through birds. By knowing the habitats birds depend on, we can then measure the threats to those habitats, and target conservation to protect and improve them. We can't conserve birds without considering habitat — the two are intimately linked.

The habitats in the WatchList are identified based on their bird communities, the Indicator Species. The habitats used by these species may not map neatly onto existing habitat maps based on vegetation and other abiotic factors. Once the habitats are identified, we can measure their level of threat from such factors as development and climate change, yielding insight into some of the most unique and endangered places in the United States and Canada.

Many bird species are generalists; they're highly mobile and less sensitive to environmental change than plants might be. But birds that are specialists — like the Kirtland's Warbler, which relies on jack pines within specific age and height ranges for breeding — are characteristic of the habitats they use. Their relationship to habitat is so strong that they may be found only in that habitat or a few very similar habitats. We call these birds Indicator Species. 

The Habitats WatchList pairs bird communities with vegetation-based habitat maps to identify terrestrial, freshwater, and coastal habitats across the U.S. (including Hawaiʻi and Alaska) and Canada. Each habitat is scored based on seven criteria such as the threatened status of the Indicator Species found there and the likelihood of future conversion or climate change impacts (see additional scoring criteria below.) The most threatened habitats are added to Red and Yellow WatchLists, below, indicating their significance to birds and the need to prioritize conservation actions in these places. 

Using the Explore App: Zoom in or out (scroll with your mouse or use the + and – buttons at the bottom of the map), or pan (click and drag) to see more or fewer habitats on the map and in the Habitat List (left). Find a specific habitat using the search bar (magnifying glass icon). 

Selecting a habitat from the Habitats List will show a range highlighted in gray on the map. Similar to a bird species' range map, the selected habitat occurs within the highlighted area, but not necessarily at every point.

Click on a habitat from the Habitat List or the map to access information in the right-hand panel. Use the arrows or tabs at the bottom of this panel to see a Habitat Description, Indicator Species present in the habitat, the habitat's overall weighted threat score, and the seven measures that make up that score.

Scoring Habitats 

The Habitats WatchList uses seven criteria to evaluate the threat level a habitat is currently experiencing:

• Bird Conservation Concern – Indicator Species in the habitat are scored based on their appearance on the Endangered Species Act (ESA; U.S.), Species at Risk Act (SARA; Canada), IUCN Red List (global), and Birds of Conservation Concern 2021. The higher the score, the more threatened the habitat's Indicator Species are.
• Number of Indicator Species – A higher score shows more Indicator Species are present, making the habitat more valuable to birds.
• Extent – Habitats with smaller areas are more threatened than larger ones. Higher scores correspond with smaller habitats.  
• Protection – Habitats with smaller proportions of protected areas are more threatened; scores are higher for those with less protected area. 
• Likelihood of Conversion – Habitats that are more likely to be converted to another habitat type through agriculture, development, or other means are more threatened and scored higher.
• Landscape Condition – Habitats in poor condition are more threatened and thus scored higher.
• Climate – Habitats more threatened by climate change are scored higher. 

A weighted sum of the scores on these seven factors can range from 10 to 100, with higher values indicating a greater level of threat to a given habitat. The highest-scoring habitats are added to the Red WatchList or Yellow WatchList, representing the habitats most at risk and requiring conservation action. 

Creating the Habitats WatchList

The concept and the identification of habitats used in the Habitats WatchList is similar to the system developed independently by Iain Campbell and coauthors in Habitats of the World and its follow-up, Habitats of North America by Iain Campbell and Philip Chaon. Though we collaborated with Iain Campbell to harmonize our habitat systems, they are not identical.

The habitats in the WatchList were determined by identifying unique bird communities composed of Indicator Species (specialists found only in one habitat, or in a few very similar habitats), joined with the vegetation categories found where these birds occur. NatureServe's vegetation classification is the basis of the Habitats WatchList map. 

Our scoring system was developed to quantify the value of a habitat to birds, and the threat level that habitat is experiencing. Some of the seven criteria outlined above used in our scoring system are based on birds, while others are based on threats to the habitat itself. Note that strictly marine habitats are not scored, and most human-made habitats (urban, suburban, tree plantations, etc.) are mapped but not scored. 

ABC thanks Iain Campbell, Princeton University Press, Philip Chaon, NatureServe, Regan Smythe, Christopher Tracey, Sara DeCaro, Hannah Ceasar, Jordana Anderson