The bird population has been declining at an alarming rate in recent decades. According to the North American Breeding Bird Survey, the overall bird population in the United States and Canada has declined by 29% since 1970. This steep drop has ornithologists and conservationists concerned about the future of our avian species. But what exactly is causing the bird population decline? There are a few key factors at play.
Habitat Loss
One of the biggest threats facing birds is habitat loss and degradation. As forests are cleared, grasslands plowed, and wetlands drained for human development, birds lose the places they need to live, find food, nest, and raise their young. Intensive agriculture has also reduced the biodiversity and ecological quality of farmlands. Estimates show that the lower 48 states have lost around 500 million acres of bird habitat since the arrival of Europeans. Deforestation in the tropics is further decimating tropical bird populations. Without large connected tracts of natural vegetation, many bird species simply cannot survive.
Climate Change
A warming climate is creating challenges for many bird species. Rising temperatures are shifting suitable habitat ranges northward and to higher elevations. However, some species cannot adapt quickly enough. The loss of habitat at southern range limits combined with the northward shift is squeezing populations between shrinking and expanding range boundaries. In addition, timing mismatches between migration and food availability are becoming more common as climate patterns change. Birds that cannot adjust their breeding cycles and migrations to match earlier spring seasons and altered food supplies are declining. Extreme weather events like droughts, wildfires, and severe storms also threaten bird populations.
Pesticides
The widespread use of pesticides and other chemicals has poisoned both birds directly and the insects they rely on as a food source. Neonicotinoids in particular have been implicated in harming bird reproduction and migration. These systemic insecticides are absorbed by plants and remain toxic through the pollen and nectar. Consequently, birds eat tainted seeds and insects, resulting in reproductive issues or death in severe cases. The 98% decline of European starlings in the Netherlands has been linked to chemical applications on cattle. Herbicides have also reduced plant biodiversity and weed seeds that birds feed on.
Light and Glass Collisions
Each year, hundreds of millions of birds die from colliding with buildings, especially glass windows and facades. Daytime collisions occur when birds fail to recognize glass as a barrier. Nocturnal migratory species are attracted to artificial night lighting, circling buildings until exhaustion causes them to crash into the glass. Chicago’s McCormick Place is estimated to kill 10,000 birds per year. Turning off unnecessary lighting at night and using bird-friendly window treatments can reduce collision fatalities.
Invasive Species
Non-native plants, animals, and pathogens introduced through global trade and travel are hurting native bird populations. In Hawaii, mosquitoes brought avian malaria that decimated the native forest birds. Feral cats and rats prey on seabirds and their eggs. European starlings compete aggressively for nesting cavities, displacing native species like bluebirds and woodpeckers. Invasive plants like cheatgrass, kudzu, and purple loosestrife degrade habitat quality and compete with native plants. Controlling invasive species and preventing new introductions protects ecosystems for native birds.
Overhunting
Some bird species are threatened by unsustainable and illegal hunting. Songbirds are poached in Europe for food, sport, or the pet trade. Raptors are shot for taxidermy specimens. Shorebirds are overhunted along migratory flyways in the Mediterranean and East Asia. Upland game birds like grouse and quail are harvested at excessive rates. Stronger hunting regulations, community engagement, and enforcement can ensure hunting is sustainable. Lead ammunition also poisons millions of birds, so transitioning to non-toxic shot helps reduce accidental mortality.
Outdoor and Pet Cats
Cats, both pet and feral, are extremely effective bird hunters. Researchers estimate cats in the U.S. kill between 1.3 to 4 billion birds each year. The most frequent victims are common songbirds like cardinals, jays, wrens, and sparrows. Cats primarily hunt birds in suburban backyards and around rural homes. Keeping pet cats indoors reduces their predation impacts. Bird-friendly collars can also help curb killing. Trap-neuter-release programs and excluding cats from sensitive habitats protects wildlife.
Power Lines
Collisions and electrocutions on power infrastructure like transmission towers and distribution lines kill millions of birds annually. Raptors like eagles and osprey are especially vulnerable because they nest and perch on utility poles. Preventative measures include retrofitting dangerous poles, insulating wires, and marking lines in high collision areas. Turning off unnecessary lighting around communication towers also reduces nocturnal bird collisions. Proper siting and configuration of new energy infrastructure can reduce risks during the development process.
Wind Turbines
Wind energy development across North America and Europe has raised concerns about bird fatalities. Birds collide with turbine blades or alter flight paths to avoid turbines, expending additional energy. Raptors and migrating songbirds are most susceptible. Strategic wind farm placement, radar monitoring, automatic turbine shutdowns, and deterrents can minimize bird deaths. More research is still needed, but wind energy impacts seem lower than other anthropogenic threats like buildings and cats.
Population Status of Common Bird Groups
Bird Group | Population Trend |
---|---|
Grassland birds | -53% decrease |
Shorebirds | -37% decrease |
Aerial Insectivores (swallows, nightjars, swifts) | -32% decrease |
Eastern forest birds | -31% decrease |
Western forest birds | -22% decrease |
Arctic birds | -19% decrease |
Waterfowl | +56% increase |
Raptors | Stable |
Urban birds | +21% increase |
This table shows population trends for major bird groups in North America since 1970 based on Breeding Bird Survey data. Grassland birds have declined the most dramatically, with over a 50% decrease over the past 50 years. Shorebirds, aerial insectivores, and forest birds have also dropped by around 30%. On the other hand, waterfowl populations have increased thanks to wetland conservation. Generalist urban birds like pigeons, starlings, and house sparrows are thriving in cities. Raptors have remained relatively stable after recovering from DDT poisoning. But other raptor species like the Eastern Loggerhead Shrike are endangered.
Case Study: Grassland Birds
Grassland birds have declined more steeply than any other bird group, with species like Eastern Meadowlark and Grasshopper Sparrow losing over 75% of their population in five decades. Intensive agriculture has eliminated pastures and hayfields these birds depend on for breeding and foraging. Native grasslands have been converted to row crops across the Great Plains and Midwest. Remaining grasslands are often heavily grazed or regularly mowed, reducing vegetation structure and food resources. Increased pesticide use has also reduced insect populations. Some ways to help grassland birds include:
- Plant native grasses and limit mowing on marginal croplands
- Use rotational grazing to improve grassland structure
- Increase pasture acreage in livestock operations
- Protect and restore remaining tallgrass prairie tracts
- Reduce persistent pesticides that limit insect prey
Partnerships between government agencies, landowners, and conservation groups can restore habitat at scales large enough to stabilize grassland bird populations. Programs like the Conservation Reserve Program pay farmers to take environmentally sensitive croplands out of production for 10-15 years.
Case Study: Aerial Insectivores
Aerial insectivores like swifts, nightjars, and swallows feed exclusively on insects caught mid-flight. But insect populations have plummeted due to pesticides, habitat loss, light pollution, and invasive species. One study found flying insect biomass in German protected areas decreased 76% over 27 years. With their food source rapidly shrinking, insect-eating birds have struggled. Chimney swifts alone declined by 95% between 1969 and 2017. To reverse declines, we must:
- Reduce agricultural pesticide applications
- Create buffer zones around waterways to increase riparian insect abundance
- Improve insect habitat diversity in forests, grasslands, and wetlands
- Increase organic agriculture and integrated pest management
- Limit light pollution which reduces nocturnal insect activity
- Preserve bat populations as a natural pest control
Bats face their own conservation threats from white-nose syndrome. But each bat eats thousands of night-flying insects daily. Ensuring healthy ecosystems with abundant native plants and reduced chemical use will provide more insects to sustain aerial insectivores.
The Importance of Birds
Birds provide essential ecosystem services and economic value worth billions of dollars annually. As pollinators and seed dispersers, birds help plants reproduce and spread. Scavenger species clean up carcasses and waste. Predatory birds control rodent and insect pests in agriculture. Birds contribute to food chains in forests, grasslands, deserts and aquatic ecosystems. Bird watching and hunting generate billions in recreational revenues. Beyond utilitarian values, birds captivate us with their beauty, songs, intelligence and freedom of flight. Our lives would be significantly poorer without birds.
How Everyone Can Help Birds
Small actions by individuals add up to make a big difference for birds. Here are simple, impactful steps anyone can take:
- Make windows bird-friendly using decals, screens, or UV-reflective glass
- Keep cats indoors – bell collars reduce kills by up to 50%
- Avoid using pesticides, opt for organic when possible
- Buy bird-friendly coffee and chocolate to protect tropical habitat
- Put up nest boxes and plant native vegetation for food and shelter
- Turn out lights during migration seasons
- Drink shade-grown coffee to boost migratory songbird habitat
- Join local birding groups and volunteer for citizen science surveys
Even converting a few lawn acres to natural vegetation makes a difference. Speak up for policies and laws that protect wetlands, restrict plastic pollution, and properly site energy infrastructure to safeguard birds. Together we can bring back the spectacular bird abundance our parents and grandparents enjoyed.
Conclusion
The declining bird population is a symptom of larger environmental degradation. Habitat loss, chemicals, climate change, and human disturbances are jeopardizing many species worldwide. But it is not too late to act. Through ecological restoration, policy reform, mitigation measures, and individual action, we can reverse bird declines. Birds are resilient – with adequate habitat, reduced threats, and protective laws, populations can bounce back. Their recovery begins in our backyards. By improving bird habitat where we live, work and play, supporting science-based conservation policies, and spreading awareness, we all contribute to a brighter future for our feathered friends.