Table 1

Net change in abundance across the North American avifauna, 1970–2017. Species are grouped into native and introduced species, management groups (landbirds, shorebirds, waterbirds, waterfowl), major breeding biomes, and nonbreeding biomes [see data S1 in (18) for assignments and definitions of groups and biomes]. Net change in abundance is expressed in millions of breeding individuals, with upper and lower bounds of each 95% credible interval (CI) shown. Percentage of species in each group with negative trend trajectories is also noted. Values in bold indicate declines and loss; those in italics indicate gains.

Species groupNo. of speciesNet abundance
change (millions) and 95% CIs
Percent change
and 95% CIs
Proportion species
in decline
ChangeLC95UC95ChangeLC95UC95
Species summary
    All N. Am. species529–2,911.9–3,097.5–2,732.9–28.8%–30.2%–27.3%57.3%
    All native species519–2,521.0–2,698.5–2,347.6–26.5%–28.0%–24.9%57.4%
    Introduced species10–391.6–442.3–336.6–62.9%–66.5%–56.4%50.0%
    Native migratory species419–2,547.7–2,723.7–2,374.5–28.3%–29.8%–26.7%58.2%
    Native resident species10026.37.346.95.3%1.4%9.6%54.0%
    Landbirds357–2,516.5–2,692.2–2,346.0–27.1%–28.6%–25.5%58.8%
    Shorebirds44–17.1–21.8–12.6–37.4%–45.0%–28.8%68.2%
    Waterbirds77–22.5–37.8–6.3–21.5%–33.1%–6.2%51.9%
    Waterfowl4134.824.548.356.0%37.9%79.4%43.9%
    Aerial insectivores26–156.8–183.8–127.0–31.8%–36.4%–26.1%73.1%
Breeding biome
    Grassland31–717.5–763.9–673.3–53.3%–55.1%–51.5%74.2%
    Boreal forest34–500.7–627.1–381.0–33.1%–38.9%–26.9%50.0%
    Forest generalist40–482.2–552.5–413.4–18.1%–20.4%–15.8%40.0%
    Habitat generalist38–417.3–462.1–371.3–23.1%–25.4%–20.7%60.5%
    Eastern forest63–166.7–185.8–147.7–17.4%–19.2%–15.6%63.5%
    Western forest67–139.7–163.8–116.1–29.5%–32.8%–26.0%64.2%
    Arctic tundra51–79.9–131.2–0.7–23.4%–37.5%–0.2%56.5%
    Aridlands62–35.6–49.7–17.0–17.0%–23.0%–8.1%56.5%
    Coasts38–6.1–18.98.5–15.0%–39.4%21.9%50.0%
    Wetlands9520.68.335.313.0%5.1%23.0%47.4%
Nonbreeding biome
    Temperate N. America192–1,413.0–1,521.5–1,292.3–27.4%–29.3%–25.3%55.2%
    South America41–537.4–651.1–432.6–40.1%–45.2%–34.6%75.6%
    Southwestern aridlands50–238.1–261.2–215.6–41.9%–44.5%–39.2%74.0%
    Mexico–Central America76–155.3–187.8–122.0–15.5%–18.3%–12.6%52.6%
    Widespread neotropical22–126.0–171.2–86.1–26.8%–33.4%–19.3%45.5%
    Widespread60–31.6–63.11.6–3.7%–7.4%0.2%43.3%
    Marine26–16.3–29.7–1.2–30.8%–49.1%–2.5%61.5%
    Coastal44–11.0–14.9–6.7–42.0%–51.8%–26.7%68.2%
    Caribbean8–6.01.4–15.712.1%–2.8%31.7%25.0%