The biodiversity crisis has come to our backyards. In less than a single human lifetime, 2.9 billion breeding adult birds have been lost from the United States and Canada, including birds in every ecosystem. Numbers have plummeted even among familiar species: the dark-eyed junco has lost an incredible 175 million individuals from its population. The white-throated sparrow has lost 93 million. To put it another way, we’ve lost more than one in every four birds since 1970.
These findings were reported in the world’s leading scientific journal, Science, by researchers at seven institutions, including American Bird Conservancy. Watch the short video highlighting the main findings and the threats behind the numbers above.
There’s no time to lose
Birds are signalling a broader crisis in the natural world — one that is echoed by global losses in insects, amphibians, and other wildlife. The disappearance of even common bird species indicates a shift in our ecosystems’ ability to support basic birdlife.
Of the nearly three billion birds lost, 90% came from just 12 bird families, including (New World) sparrows, (New World) warblers, finches, and swallows. These common, widespread species play influential roles in ecosystems. If they’re in trouble, the wider web of life, including us, is in trouble, too.
Behind the numbers
This is the first study to undertake an accounting of the net population changes across a total of 529 breeding bird species in the United States and Canada. The researchers analysed birds on a group-by-group basis, allowing them to identify declines among species that use similar habitats. The findings included 48 years of data from multiple independent sources, including the North American Breeding Bird Survey and the Christmas Bird Count. A comprehensive analysis of 11 years of data from 143 NEXRAD radar stations showed a similarly steep decline in the magnitude of migration.
Where the losses are
A number as big as 2.9 billion is hard to fathom. Look at it like a balance sheet. Each year, many birds produce young while many others die. But since 1970, on balance, many more birds have died than have survived, resulting in 2.9 billion fewer breeding birds today.
Some ecosystems show worse losses than others. For example, forests alone have lost one billion birds since 1970. Grassland birds are also hard hit, with a 53% reduction in population — more than 720 million birds. Aerial insectivores — birds like swallows, nighthawks and flycatchers — are down by 32%, or 160 million. Coastal shorebirds, already at dangerously low numbers, lost more than one-third of their population.
The volume of spring migration, measured by radar in the night skies, has dropped by 14% in just the past decade.
Drivers of decline
Although the study did not investigate causes, scientists have identified that habitat loss is the biggest overall driver of bird declines. Habitat loss occurs when land is converted for agriculture, development, resource extraction, and other uses. Habitat degradation is a second cause of losses. In this case, habitat doesn’t disappear outright but becomes less able to support birds, such as when habitat is fragmented, altered by invasive plants, or when water quality is compromised.
Aside from habitat loss and degradation, other major human-caused threats to birds come from cats and other invasive species; collisions with glass and industrial infrastructure such as communications towers and wind turbines; and exposure to pesticides and other toxics.
Climate change is expected to exacerbate these threats, as well as creating new challenges; for example, changing habitat distributions and shifting the timing of peak food supplies for birds.
Fortunately, individuals can take action to reduce many of these threats. Learn more about ways you can help birds through everyday actions.
Help combat the crisis
ABC’s “50-50-5” plan in North America is designed to address the current bird crisis there. It will make a transformational difference for birds, and at the same time, protect millions of additional species of plants and animals, and make a huge contribution to solving our planet’s biodiversity and climate crises.
The plan is to save 50 flagship bird species, protect and conserve 50 million acres, and fight five critical threats. Can we do the same in Europe?
Download a manuscript of the full study Decline of the North American Avifauna here.