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 group | No. of species | Net abundance change (millions) and 95% CIs | Percent change and 95% CIs | Proportion species in decline | ||||
| Change | LC95 | UC95 | Change | LC95 | UC95 | |||
| Species summary | ||||||||
| All N. Am. species | 529 | –2,911.9 | –3,097.5 | –2,732.9 | –28.8% | –30.2% | –27.3% | 57.3% |
| All native species | 519 | –2,521.0 | –2,698.5 | –2,347.6 | –26.5% | –28.0% | –24.9% | 57.4% |
| Introduced species | 10 | –391.6 | –442.3 | –336.6 | –62.9% | –66.5% | –56.4% | 50.0% |
| Native migratory species | 419 | –2,547.7 | –2,723.7 | –2,374.5 | –28.3% | –29.8% | –26.7% | 58.2% |
| Native resident species | 100 | 26.3 | 7.3 | 46.9 | 5.3% | 1.4% | 9.6% | 54.0% |
| Landbirds | 357 | –2,516.5 | –2,692.2 | –2,346.0 | –27.1% | –28.6% | –25.5% | 58.8% |
| Shorebirds | 44 | –17.1 | –21.8 | –12.6 | –37.4% | –45.0% | –28.8% | 68.2% |
| Waterbirds | 77 | –22.5 | –37.8 | –6.3 | –21.5% | –33.1% | –6.2% | 51.9% |
| Waterfowl | 41 | 34.8 | 24.5 | 48.3 | 56.0% | 37.9% | 79.4% | 43.9% |
| Aerial insectivores | 26 | –156.8 | –183.8 | –127.0 | –31.8% | –36.4% | –26.1% | 73.1% |
| Breeding biome | ||||||||
| Grassland | 31 | –717.5 | –763.9 | –673.3 | –53.3% | –55.1% | –51.5% | 74.2% |
| Boreal forest | 34 | –500.7 | –627.1 | –381.0 | –33.1% | –38.9% | –26.9% | 50.0% |
| Forest generalist | 40 | –482.2 | –552.5 | –413.4 | –18.1% | –20.4% | –15.8% | 40.0% |
| Habitat generalist | 38 | –417.3 | –462.1 | –371.3 | –23.1% | –25.4% | –20.7% | 60.5% |
| Eastern forest | 63 | –166.7 | –185.8 | –147.7 | –17.4% | –19.2% | –15.6% | 63.5% |
| Western forest | 67 | –139.7 | –163.8 | –116.1 | –29.5% | –32.8% | –26.0% | 64.2% |
| Arctic tundra | 51 | –79.9 | –131.2 | –0.7 | –23.4% | –37.5% | –0.2% | 56.5% |
| Aridlands | 62 | –35.6 | –49.7 | –17.0 | –17.0% | –23.0% | –8.1% | 56.5% |
| Coasts | 38 | –6.1 | –18.9 | 8.5 | –15.0% | –39.4% | 21.9% | 50.0% |
| Wetlands | 95 | 20.6 | 8.3 | 35.3 | 13.0% | 5.1% | 23.0% | 47.4% |
| Nonbreeding biome | ||||||||
| Temperate N. America | 192 | –1,413.0 | –1,521.5 | –1,292.3 | –27.4% | –29.3% | –25.3% | 55.2% |
| South America | 41 | –537.4 | –651.1 | –432.6 | –40.1% | –45.2% | –34.6% | 75.6% |
| Southwestern aridlands | 50 | –238.1 | –261.2 | –215.6 | –41.9% | –44.5% | –39.2% | 74.0% |
| Mexico–Central America | 76 | –155.3 | –187.8 | –122.0 | –15.5% | –18.3% | –12.6% | 52.6% |
| Widespread neotropical | 22 | –126.0 | –171.2 | –86.1 | –26.8% | –33.4% | –19.3% | 45.5% |
| Widespread | 60 | –31.6 | –63.1 | 1.6 | –3.7% | –7.4% | 0.2% | 43.3% |
| Marine | 26 | –16.3 | –29.7 | –1.2 | –30.8% | –49.1% | –2.5% | 61.5% |
| Coastal | 44 | –11.0 | –14.9 | –6.7 | –42.0% | –51.8% | –26.7% | 68.2% |
| Caribbean | 8 | –6.0 | 1.4 | –15.7 | 12.1% | –2.8% | 31.7% | 25.0% |