Bird species and populations are in decline

“Over increasingly large areas of the United States, spring now comes unheralded by the return of the birds, and the early mornings are strangely silent where once they were filled with the beauty of bird song.”

— Rachel Carson, Silent Spring (1962)

The rise and fall of bird populations has long been an indicator of environmental health, perhaps best evidenced by Rachel Carson’s call to action in her bestseller Silent Spring. By the 1960s, widespread use of pesticides such as DDT caused an alarming decline in bald eagle nesting pairs to just 417 for the entire lower United States. Silent Spring’s description of the decline in bird populations due to pesticide use was a clarion call that led to the EPA banning the pesticide DDT. Today, there are now over 71,400 nesting pairs as a result of Rachel Carson’s book and the EPA’s subsequent action, and birds, other animals, people, and ecosystems all have benefited from the increased attention to curbing pesticide use. The hopeful recovery of eagles and other raptors shows the impact that long-term observations have in bird populations as well as the important role that they continue to play today.

Long-term observations (LTOs) – like bird counts that record species’ abundance and ranges throughout decades, or measurements of atmospheric carbon dioxide over time that create the Keeling Curve graph – are quantitative observations, measurements, samples, or records of a subject taken at repeated intervals over a long period of time. These environmental measurements mark waypoints in the past and present and show possible paths beyond. Long-term data sets like these are imperative for scientific research that impacts people and ecosystems around the globe.

Unfortunately, long-term observations themselves are in peril due to funding challenges. The Keeling Curve Foundation’s unique mission is to support and promote long-term environmental observations. The Keeling Curve Foundation works to identify long-term observations at risk and increase awareness of the purpose and impact of long-term monitoring programs worldwide. These programs are essential for understanding our present world and for forecasting our future.

Learn more about long-term observations

Diminishing bird populations detected by long-term observations

Recent long-term studies have found startling global declines in diversity and abundance attributed to human causes, culminating in a loss of three billion birds over the past five decades. That's roughly a 25% decline in bird abundance.

Declining populations aren't just limited to threatened or vulnerable species such as raptors — common and backyard bird species that we know and love are experiencing unprecedented losses as well.

BirdLife International’s 2022 State of the World’s Birds reports that nearly half of the 10,000 bird species around the world are in decline, and more than one in eight bird species is threatened with extinction. The 2022 State of the Birds report from the U.S. Committee of the North American Bird Conservation Initiative (NABCI) recognized that 70 different "tipping point" species have lost at least half of their breeding population since 1970. These declines are occurring in all habitat types except wetlands due to dedicated fiscal and political investment in wetland conservation. The National Audubon Society's 2019 report "Survival by Degrees: 389 Bird Species on the Brink" highlighted the threat of extinction for two-thirds of North American birds due to climate change.

Declines due to multiple environmental causes

Much like the proverbial canary in the coal mine, birds are sentinels of environmental and climatic change. Around the world, bird species are monitored for exposure to harmful chemicals like pesticides, disease, habitat changes, and more. Birds are sensitive to small fluctuations around them and these changes often result in altered behaviors or abundance. Observing and monitoring birds over long periods of time can help scientists identify environmental trends and changes in local or regional climate.

Because birds live in almost every ecosystem, they are affected by multiple environmental issues. Changes in habitat type or availability, climate, and other environmental parameters around the world can alter or reduce the range (or physical distribution) of bird species, especially those with finely-honed ecological niches.

Factors causing bird decline include habitat loss, changes in diet due to declining insect populations, increased light pollution from commercial buildings causing fatalities during migration, increased levels of harmful or toxic chemicals such as pesticides introduced in ecosystems, and climate shifting outside of species’ tolerable ranges. The impacts are worsened when multiple stressors exist together.

Climate change impacts on birds

The effects of climate change are a key part of declining bird populations and species loss. Some areas, such as the western United States and much of Europe, are becoming hotter and drier, and extreme weather is becoming more commonplace. As droughts from reduced precipitation become more intense, this can limit habitats and nesting areas, alter birds' food sources such as plants and insects, and increase the risk of wildfires. In other regions, extreme precipitation and storms can cause severe flooding inland and along coasts, resulting in similar disruptions to native habitats and ecosystems.

Climate change produces multiple impacts that collectively heighten risks to ecosystems, and these impacts can compound to create intolerable conditions for species. For example, timing, or phenological, shifts in bird migratory cycles due to atmospheric temperature changes can cause a mismatch in timing between birds and availability of their insect prey. Other areas like shoreline nesting sites are at risk of being inundated due to rising sea levels and more frequent flooding. Extreme weather events can alter birds' behavioral patterns, and climate shifts can alter the pervasiveness of disease threatening birds.

To explore climate impacts on birds across North America, the Audubon's Survival By Degrees report features an interactive tool including different warning scenarios and seasonality, vulnerable species counts, species' range and migration maps, and more. Subscribers to the Washington Post can also visit this Climate Lab article to interactively view how local bird species are faring.

What can you do? Contribute to community science by counting birds

Community scientists observe and record bird sightings.

Collecting long-term observational data on birds is essential to identifying and tracking trends in species diversity and the abundance and range of different species. There are many ways to help monitor bird populations and support observational data collection from your own backyard or surrounding wild spaces. You can contribute information about the birds you spot and identify through community science platforms such as eBird from the Cornell Lab of Ornithology. This app is an easy way to record your own local bird sightings and to view observational trends by other users around the country.

The many individual sightings collected by eBird enable ornithologists to examine bird species richness and abundance data at scale: across large regions and over long periods of time. These and other LTO data can be compiled to create thorough and authoritative reports of the fates of regional and global bird species and populations. Beyond the North American continent, Bird Library has a handy list of field guide apps for birding and identification in just about every region of the globe.

Community science programs (aka citizen science programs) that compile amateur observations across regions over time are valuable in identifying and following data trends. These programs record many observations over a broad temporal and spatial scale using standardized collection methods, creating robust databases that are useful to scientists and decision-makers.

Ensuring community science rigor

Community bird counts rely on volunteers to submit data that can be aggregated and used in scientific reports. How do we know the collected data is accurate? Because observers’ effort and levels of expertise can vary, established trainings, clear protocols, and methods of data validation are essential. As with other community science programs, bird counts follow standardized methods for volunteer training, data collection and submission. Data quality controls and verification validate data and minimize bias. Rigor is ensured when academics collaborate with community scientists, such as the data partnership between the Cornell Lab of Ornithology and eBird. Through these standardized methods, citizen scientists and organizations are assured of robust, accurate, and high-quality data for scientific research and environmental monitoring. Standardized methods include:

Volunteer Training

Bird count participants undergo training via online courses, receive instructions from count coordinators or sector leaders, and utilize field guides.

Experienced field leaders guide volunteers on protocols for specific bird count events, such as the Christmas Bird Count.
Organizations readily provide community guidelines and protocols which participants are expected to follow during counting events.
Volunteers can utilize help centers, community support, instructional trainings and articles, and advice from count coordinators before and during count events.

Data Collection and Counting Standards

Specific protocols for what, when, where, and how birds are counted assures that all volunteers are collecting data the same way for each counting program and event.
Participants are instructed to identify birds they hear and see and to report bird counts within a specific timeframe and geographic area.
Organizations such as eBird provide specific guidelines on how to count birds, from groups of one species to many birds of different species.
Beyond the type/species and number of birds observed in a certain area or time period, counters are sometimes asked to record additional data. For example, the Christmas Bird Count asks participants to record all birds that they see and hear, the time spent observing, miles traveled, mode of transportation, and to designate which observations were made during daylight or evening (nocturnal birding) hours.

Data Submission and Quality Control

Counters submit their observations using digital platforms, such as eBird, or to their count coordinators using standardized formats like checklists.
Observational data is validated through automated filtering as well as manual reviews by regional experts, which helps flag any improper data entries, misidentified species, or unusual species or counts in a certain location or season.
Counters are encouraged to include photo or audio documentation for sightings of unusual or rare bird species to help validate their observations.

Community scientists at the Audobon’s Christmas Bird Count

What do we lose when we lose our birds?

Birds provide innumerable ecosystem services. They act as pollinators, are a source of fertilizer, and help control insect populations. Certain bird species – including owls, hummingbirds, woodpeckers, puffins, and red-tailed hawks, to name a few – are keystone species integral to their ecological network. Woodpeckers serve as ecosystem engineers by boring cavities in wood, creating new habitats for other birds and forest animals like bats, raccoons, and squirrels. Bird species such as these are ecologically vital and changes in their abundance can have intense cascading effects within their ecosystems.

Birds and humans have been inextricably linked throughout history. We know them as masters of navigation, inspirations for human flight, mournful and joyous singers, and heralds of dawn, dusk, and the changing seasons. Often our most immediate and daily connection to nature, birds have served as sacred figures, spiritual guides, hunting partners, sources of food and clothing, artistic and literary muses, and symbols of beauty, diversity, and freedom for thousands of years. Sixty years after Rachel Carson’s pioneering book, community science continues to play an important role in documenting these sobering changes. Monitoring programs like these, and the data they provide, are central to the Keeling Curve Foundation’s mission to advance, promote, and protect long-term environmental observations.

Observing bird populations across the world – and over time – helps indicate where we should take action to support and protect bird species. In this way, we can bring birds back from the brink.

Learn about how you can get involved with bird counting

The Value of Watching Birds Over Time