Three in five, and falling
Of every five bird species on Earth, three now have shrinking populations. 61% of all bird species are in decline — and that share is climbing fast: it was 49% in 2022 and 44% nine years before that1. The birds outside your window — sparrows, starlings, swifts, the common species nobody worried about — are the ones quietly emptying out.
A declining population isn’t the same as an endangered species; it’s the earlier warning. A bird can be abundant and still be in steep decline, which is exactly what’s happening to the everyday species. The trajectory here isn’t just downward — it’s accelerating.
of the world's bird species have shrinking populations — up from 44% just nine years ago
Worse, and faster
Three data points, drawn from successive updates of the same global assessment process:
| Year | % of bird species in decline | Source |
|---|---|---|
| ~2015 | 44% | IUCN Red List, baseline period |
| 2022 | 49% | BirdLife State of the World’s Birds2 |
| 2024 | 61% | IUCN Red List 2024 update1 |
That’s a 17-percentage-point increase in nine years — roughly two percentage points per year, and the rate itself is rising. Whatever’s killing birds is doing so faster than the conservation infrastructure can absorb.
Separately, 12% of bird species (about 1,400) are threatened with extinction by IUCN criteria1. That figure is more stable year-to-year because moving a species between Red List categories requires sustained evidence — the population-decline figure picks up trends earlier.
It’s the land, again
BirdLife International’s State of the World’s Birds 2022 report ranked the pressures on globally threatened bird species2:
- Agriculture: 73% of threatened species. Crop expansion, intensification, monocultures, pesticide use.
- Logging: 50%. Selective and clear-cut, particularly in tropical forests.
- Invasive species: 43%. Devastating on islands; rats, cats, mosquitoes carrying avian malaria.
- Hunting and trapping: 41%. Subsistence, trade, persecution.
- Climate change: 37%. Range shifts, phenological mismatches, extreme weather.
The agricultural driver is the same one driving vertebrate populations down 73% globally and the collapse of insect biomass. Many declining bird species are insectivores — fewer insects, fewer birds.
The terrestrial insect index is falling ~9% per decade globally. Most insectivorous birds depend on this disappearing food base.
The North American case study: 3 billion birds gone
The single most-cited regional bird-decline study is Rosenberg et al.’s 2019 Science paper3. Using three independent monitoring methods — the North American Breeding Bird Survey, weather-surveillance radar, and species-specific censuses — the team found:
- North America has lost roughly 2.9 billion breeding birds between 1970 and 2017
- That’s a 29% reduction in total bird abundance — roughly one in four birds gone
The losses were not evenly distributed:
- Grassland birds: −53%. Loss of ~720 million individuals. Driver: conversion of prairies to cropland.
- Boreal forest birds: −33%. ~500 million lost.
- Migratory shorebirds: −37%.
- Wetland birds: +13%. Beneficiary of the 1971 Ramsar Convention and the U.S. Clean Water Act.
- Raptors: +200%. Direct beneficiary of the 1972 DDT ban. Bald eagles, peregrine falcons, ospreys — one of the most successful intervention stories in conservation history.
The split says something important about leverage: bird populations respond to policy. Where there’s been concerted intervention, populations have recovered. Where there hasn’t, they’ve collapsed. The same pattern, at the same scales, applies globally.
The line, extended
The line heads toward 75% of bird species in decline by 2050 — a deliberately capped extrapolation rather than a straight linear projection.
A pure linear extrapolation of the recent rate (17 points over 9 years) implies ~110% by 2050 — mathematically impossible, since you can’t have more than 100% of species in decline. We cap the projection at 75% to reflect realistic ecological saturation: the most resilient ~25% of species (urban adapters, generalists, populations in well-managed refuges) are unlikely to enter decline at the same rate as the rest.
This is a low-confidence projection by design. We disclose it as one. The headline number — 61% in decline today, 17 points up in nine years — does most of the work on its own.
The mammals story by the same metric: 47% of large mammals are threatened with extinction.
Birds come back when we let them
The Rosenberg paper that documented the 3-billion-bird loss in North America also documented the recoveries — and the recoveries are real. Eagles, falcons, ducks, geese have all rebounded under specific policy interventions: pesticide bans, wetland protections, habitat-dedicated funding.
The implication: the broader bird decline is a policy choice, not a natural inevitability. The interventions that worked for raptors and waterfowl — concrete, fundable, replicable — have not yet been applied at the scale needed for grassland and forest birds globally.