Why Are North America’s Birds Disappearing?

North America has lost over a quarter of its bird population in just a few decades, with even once-common species now vanishing at alarming rates

A recent study highlighted by The Guardian reports that three-quarters of nearly 500 bird species across North America are in decline, with the most significant drops occurring in regions once considered avian strongholds. This isn't just about fewer birds at feeders or quieter mornings; it's a clarion call signalling profound shifts in our ecosystems. Birds, often seen as indicators of environmental health, are vanishing at an alarming rate, prompting urgent questions about the underlying causes and what actions we must take to halt this trend

Three-quarters of nearly 500 bird species across North America are in decline.

A Staggering Decline Across a Continent

Scientists have been tracking the decline of birds for years, but the latest findings are stark. Using millions of observations from ordinary birdwatchers, researchers mapped population trends for nearly 500 bird species across North America – one of the most ambitious citizen-science analyses ever. The results were shocking: three-quarters of these species are in decline, and two-thirds are shrinking significantly in population. In other words, only a minority of bird species are holding their own. Even traditionally common birds are dwindling. All told, North America has lost around 2.9 billion birds since 1970, more than one in four of all the birds that once filled our skies. As Cornell Lab director John Fitzpatrick described it, this is “a staggering loss” – as if the very fabric of North America’s ecosystem is unravelling.

Common sparrows, warblers, blackbirds and finches – backyard favourites – have suffered some of the steepest losses. The cheerful Dark-eyed Junco (sometimes called the “snowbird”) has lost an estimated 168 million individuals from its population, and the sweet-singing White-throated Sparrow is down by 93 million. Eastern and Western Meadowlarks, once abundant in prairie grasslands, have together lost about 139 million individuals. Even the ubiquitous Red-winged Blackbird, a staple sight in marshes and roadside ditches, has declined by around 92 million birds. These aren’t obscure or endangered species – they are the hardy, familiar birds that form the background of US life. Their decline is a loud alarm bell.

Perhaps most worrying, the new study found that the steepest drops are occurring in the very places where birds used to thrive. In former bird strongholds – the great grassland prairies, the arid drylands of the west, even the remote forests and tundra of the Arctic – numbers are plummeting fastest. It’s a bitter twist: the regions that once provided safe haven for wildlife are becoming epicentres of loss.

Why Are the Birds Disappearing?

Unravelling the causes of this collapse isn’t straightforward. Birds are telling us that something is off-kilter in the environment, but what exactly? Habitat loss and climate change emerge as the two chief culprits in scientists’ minds. Over the past century, humans have radically reshaped North America’s landscapes. Grasslands have been ploughed under for agriculture, wetlands drained, forests cut down for timber or development. The expansion of intensive agriculture – endless monoculture fields and heavy pesticide use – means there are fewer wildflower meadows and insect-rich fields, which spells trouble for insect-eating birds and seed gatherers alike. When a prairie becomes a pesticide-treated cornfield, meadowlarks and sparrows have no place to nest or feed. As one global assessment noted, the expansion of agriculture and logging has put pressure on nearly 3 out of 4 bird species worldwide. North America is no exception.

Then there’s the climate crisis. Global warming is shifting seasons and unleashing more extreme weather. Migratory birds time their journeys to traditional cues like temperature and daylight – but with earlier springs and erratic weather, they may arrive to find that the peak of insect food they rely on has already passed. Prolonged droughts in the western drylands eliminate the water sources that waterfowl and songbirds need. In the far north, warming disrupts the delicate food webs that sustain birds like the snowy owl and the Arctic tern. The new study’s authors suggest that climate change is likely a major driver behind the mysterious declines observed in once-pristine areas. The environment is changing faster than many species can adapt.

The expansion of intensive agriculture is one of the factors behind the decline in bird numbers.

Beyond these, a host of other human-driven threats are chipping away at bird numbers. Pesticides not only eliminate insects (a critical food source for many birds) but can also poison birds directly. Invasive species and diseases are affecting native bird populations. And on top of the ecological changes, there are direct killers: for example, free-roaming domestic cats are estimated to kill over 2 billion birds every year in the U.S. alone, making cat predation the single largest human-caused source of bird mortality. Collisions with glass windows and buildings are another major cause, killing hundreds of millions of birds annually as they migrate through our cities. All these factors together create a perfect storm for birds. The researchers admit they don’t yet fully know why birds are vanishing fastest in their former safe havens – more studies are needed – but it’s clear that our human footprint is at the centre of the story.

We Can Bring Birds Back

The situation is dire, but not hopeless. The same study that documented these declines also found pockets of hope – literally. In a few places, bird populations are holding steady or even increasing, such as parts of the Appalachian Mountains. In fact, 97% of species studied had at least some areas where their numbers were growing, showing that when conditions are right, birds can bounce back. We have the knowledge and tools to help nature recover; now we need action at every level.

The story of North America’s birds is still being written. While the losses have been huge and sobering, the flickers of resilience seen in some areas show that if we give nature a chance, it can recover. We are fortunate that many bird species, given protection and suitable habitat, can rebound relatively quickly. There are success stories to inspire us – from the comeback of the bald eagle after DDT was banned, to wetlands restoration efforts that have boosted waterfowl numbers. Every individual and community effort, combined with bold policy changes, adds up. It’s the sum of many small actions and a few big ones. The Age of Extinction that scientists warn about is not inevitable – it’s a choice we make by action or inaction.