Why are grassland birds declining?

Grassland birds have been declining at alarming rates across North America over the past 50 years. According to research, grassland bird populations have declined by over 50% since 1970. There are several major factors that have contributed to these declines which this article will explore.

Habitat Loss

The single biggest threat to grassland birds is habitat loss. Grasslands have been converted at rapid rates to farmland, urban development, and other human uses. It is estimated that tallgrass prairie habitats have declined by over 99% since European settlement. Mixed grass prairies have declined by around 90%. This extensive loss of native grasslands has severely reduced the available breeding and nesting grounds for many grassland bird species.

Birds such as Bobolinks, Eastern Meadowlarks, Grasshopper Sparrows and Dickcissels rely on large expanses of tall grass prairie habitat for nesting. As this habitat has disappeared across their breeding range, so have the bird populations. Between 1966 and 2013, Bobolink populations declined by over 60%. Their remaining breeding habitat is now highly fragmented, leaving them more vulnerable to nest parasites and predators.

Changes in Agricultural Practices

Modern agricultural practices have also had detrimental effects on grassland birds. The shift to industrial farming techniques and monoculture row crops has reduced biodiversity in agricultural grasslands. Highly managed croplands provide lower quality habitat compared to mosaic style farming practices such as mixed livestock grazing and small scale crop rotations.

Earlier harvesting of hay and small grain crops have negatively impacted ground nesting species. The switch from spring to early summer harvesting decreases vegetative cover and exposes early nests to equipment and predators. In Wisconsin, earlier hay harvests were associated with 27 times higher failure rates for Grasshopper Sparrow nests.

Increased pesticide use on croplands has reduced food availability. Common pesticides such as neonicotinoids have been shown to negatively impact bird reproduction and survival. Herbicide use decreases plant diversity resulting in less cover and seeds for grassland birds.

Lack of Disturbance

Natural disturbances such as grazing, wildfires and floods help maintain native grasslands. Historically, American Bison grazed extensively across the Great Plains. Their movement and grazing helped create diverse grassland habitats. Active prairie dog colonies can also provide suitable habitat for some species.

With human settlement, these natural disturbance regimes have been lost. Most remaining grasslands lack the grazing, burrowing mammals and other disturbances that grassland birds evolved with. As a result, many areas become overgrown with dense, woody vegetation and exotic grasses. This reduces habitat suitability for bird species adapted to sparser and more diverse grassland vegetation.

Invasive Species

The introduction of invasive plant species has degraded grassland bird habitat. Invasive grasses such as Kentucky Bluegrass, Smooth Brome and Reed Canary Grass have taken over many prairies. These tall, dense exotic grasses outcompete diverse native plants. They often form monocultures providing poor nesting habitat compared to native vegetation.

Tree encroachment into open grassland from species like Eastern Red Cedar has also reduced habitat. Encroachment of wooded edges creates predator corridors and nest parasites such as Brown-headed Cowbirds have greater access to interior grassland bird nests. Cowbirds lay their eggs in other bird nests, reducing nest productivity.

Climate Change

Climate change poses an emerging threat to grassland birds. Changing weather patterns and increased frequency of drought and severe weather events may impact nesting success. Grassland birds time their breeding and migration to coincide with peak food availability. As climate change disrupts phenology between plants, insects and wildlife it could negatively affect reproduction.

Rising temperatures may also enable expanding ranges of predators, invasive species and diseases into grassland bird habitat. Grasslands are predicted to be more vulnerable to the impacts of climate change compared to other ecosystems.

Conservation Actions and Solutions

Despite declining trends, there are conservation actions being implemented to protect grassland birds and restore their habitats:

• Protecting and properly managing existing public and private grasslands through controlled grazing, prescribed burns and woody vegetation removal
• Restoring native prairie habitats on marginal croplands via the Conservation Reserve Program and other initiatives
• Improving grassland habitat on working lands by providing financial incentives to farmers and ranchers
• Working with rural and agricultural communities to implement more grassland bird friendly practices
• Supporting market-based conservation by creating demand for grass-fed beef and other sustainable grassland products
• Controlling invasive vegetation and limiting further woody encroachment into open grasslands
• Monitoring and researching population trends and habitat use to inform effective management
• Educating the public on the importance of grassland conservation and how they can help

More ambitious large-scale conservation efforts focusing on creating habitat corridors may be needed to support viable populations of grassland bird species. Broader adoption of regenerative grazing practices could benefit both birds and ranchers.

While the task is daunting, strategic habitat conservation focused on priority areas and species, along with policy changes to support sustainable grassland management, can help reverse declining trends.

Major Grassland Bird Species Declining

Here are some of the grassland bird species that have experienced significant population declines over the past 50 years according to the North American Breeding Bird Survey:

Other species showing substantial declines include Grasshopper Sparrow, Eastern Meadowlark, Bobolink, Short-eared Owl, Northern Bobwhite, Loggerhead Shrike, and Vesper Sparrow.

Threats Facing Major Grassland Bird Species

Here is a more detailed look at some of the major threats and conservation concerns for key grassland bird species:

Greater Prairie-Chicken

• 85% decline in population since surveys began in the 1960s
• Restricted to isolated fragments of prairie in 11 U.S. states and Canada
• Requires large tracts of grasslands with diverse native vegetation structure
• Threatened by further habitat fragmentation and degradation
• Vulnerable to weather events and changing climate

Lesser Prairie-Chicken

• Once abundant, estimated 97% decline from historical levels
• Habitat loss and degradation from agriculture and energy development
• Drought and climate change impacting breeding success
• Collisions with fences and vehicles
• Planned protections under Endangered Species Act blocked due to political opposition

Loggerhead Shrike

• 71% population decline from 1970-2014
• Human disturbances and habitat loss on wintering grounds and migration routes
• Increased pesticide use reduces prey availability
• Collision mortality from barbed-wire fences
• Declining songbird populations contributing to food limitations

Henslow’s Sparrow

• Up to 90% population decline since 1960s
• Only about 75,000 individuals remaining
• Dependent on large patches of tallgrass habitat with dense litter layer
• Poor nest success when litter layer is sparse
• Threatened by any loss or degradation of remaining habitat

Positive conservation efforts for some species have helped stabilize populations in certain regions. However, many species require urgent action to avoid extinction and recover to sustainable levels.

Importance of Grassland Birds

Grassland birds play important roles in their ecosystems. Their declines can have cascading effects on biodiversity and habitat health. Here are some key reasons grassland birds matter:

• Insect control – Many species provide natural pest control by consuming crop damaging insects like grasshoppers and locusts.
• Seed dispersal – Birds help disperse and germinate native plant seeds vital for prairie restoration.
• Nutrient cycling – Droppings from grassland birds fertilize soils and provide nutrients for plant growth.
• Prey base – Birds are an important prey species for predators like hawks and foxes.
• Ecosystem balance – Complex bird-mammal-insect food webs can collapse if keystone species disappear.
• Environmental awareness – Grassland birds make people appreciate prairie ecosystems and support conservation.

Grassland birds also contribute to natural beauty, culture and recreation. Conserving birds protects biodiversity, maintains healthy ecosystems and benefits both wildlife and people.

Outlook for Grassland Bird Conservation

The outlook for grassland birds remains concerning but not without hope. While many species have witnessed catastrophic declines, there are viable pathways for recovery through collaborative conservation efforts. This will require:

• Expanded protected areas and restoration of native grasslands across breeding, migration and wintering ranges
• Science-based habitat management focused on priority species and locations
• Incentives for landowners to implement grassland bird friendly practices
• Market-based solutions to increase demand for sustainable grass-fed beef and grassland products
• Mitigation of climate change and enhancement of landscape resilience
• Funding for long-term monitoring, research and adaptive management
• Overcoming political and socioeconomic barriers to conservation
• Engagement of diverse stakeholders – landowners, agencies, NGOs and the public

With broad cooperation, restored grassland habitats integrated across working agricultural lands can support viable bird populations. The balance between production and conservation will require compromise from all sides. But focused efforts today will mean birds singing on the prairies for generations to come.