Prairie-chickens are a species of grouse native to the prairies of central North America. They once numbered in the millions, but habitat loss has caused their populations to plummet dramatically. Today, prairie-chickens are considered a vulnerable species and conservation efforts aim to protect remaining populations. An important factor in prairie-chicken conservation is understanding how much habitat they require to sustain viable populations. This article will examine the habitat needs of prairie-chickens and discuss estimates for how many acres they require.
Background on Prairie-Chickens
Prairie-chickens (Tympanuchus cupido) are a medium-sized species of grouse belonging to the family Phasianidae. There are two distinct subspecies:
- Greater prairie-chicken (T. c. pinnatus) – Occupies tallgrass prairie habitat
- Lesser prairie-chicken (T. c. pallidicinctus) – Occupies shortgrass and mixed-grass prairie habitat
Historically, prairie-chickens could be found from Canada to Texas, inhabiting virtually all types of prairie habitat. They are best adapted to native prairie and require large, open expanses of grasslands. Prairie-chickens play important roles in prairie ecosystems as prey species and by positively impacting plant communities.
Over the last two centuries, agricultural expansion and development have destroyed over 90% of native prairie habitat across the Great Plains. This habitat loss has caused greater prairie-chicken populations to decline by over 90% and lesser prairie-chicken populations to decline by 97%. Due to these severe population reductions, both subspecies are currently listed as “vulnerable” on the IUCN Red List.
Life History
Prairie-chickens have unique behavioral adaptations to prairie environments. They are non-migratory, remaining in the same area year-round. Males gather at communal breeding grounds called leks each spring to perform elaborate mating displays. Nesting occurs in grasslands near the lek, with females laying clutches of around 12 eggs. Chicks are able to fly short distances after two weeks and reach full size after three months. On average, prairie-chickens live for 1-2 years.
Throughout the year, prairie-chickens spend most of their time on the ground eating seeds, leaves, and insects. They prefer habitats with a diverse mix of native grasses and forbs. Vegetation height and density are also important, as prairie-chickens require areas of bare ground as well as taller grasses and shrubs for nesting cover. These specific habitat needs highlight why conserving adequate prairie acreage is so critical.
Habitat Area Requirements
Researchers have worked to estimate how much contiguous habitat prairie-chickens need to maintain stable populations. These estimates provide conservation targets for protecting and restoring prairie landscapes. Studies suggest that the area requirements may differ between the two subspecies and populations in certain geographic regions. Overall, published estimates indicate that viable prairie-chicken populations likely need thousands to tens of thousands of acres of habitat.
Greater Prairie-Chickens
Several studies of greater prairie-chickens have produced acreage recommendations:
– A 2007 study in Kansas recommended at least 10,000 acres of contiguous habitat to support a stable population. Smaller habitat blocks of around 1,000 acres may support small groups, but populations are more vulnerable.
– In 2018, researchers analyzed population viability across the entire greater prairie-chicken range. Their models predicted that blocks of at least 25,000 acres of habitat were needed for a >95% probability of persistence over 100 years.
– A metanalysis in 2020 concluded that protected habitat areas between 25,000 and 50,000 acres would provide reasonable security for greater prairie-chicken populations.
Based on these findings, conserving blocks of intact grasslands on the order of 25,000-50,000 acres or more appears optimal for greater prairie-chickens. However, smaller habitat patches down to 1,000 acres may still provide marginal habitat if clustered together in a complex.
Lesser Prairie-Chickens
Habitat requirements have also been evaluated for lesser prairie-chickens:
– In New Mexico, models predicted 2,100 acres of shinnery oak sand dune habitat could support 100 lesser prairie-chickens. Larger habitat blocks would be needed for long-term viability.
– Oklahoma researchers calculated that habitat patches of at least 7,900 acres were needed to regularly support lesser prairie-chicken leks. Areas up to 12,500 acres were optimal.
– Analysis of population persistence across the five-state lesser prairie-chicken range found a minimum habitat block size of 58,000 acres was needed for a >95% 100-year persistence probability.
These findings suggest that ideal lesser prairie-chicken habitat would be arranged in minimally fragmented blocks of 25,000-60,000 acres. Smaller patches of around 8,000 acres may be inhabitable but would need to be closely clustered. Compared to greater prairie-chickens, lesser prairie-chickens may require larger habitat blocks, likely due to their restriction to drier, more fragmented shortgrass prairie habitat.
Regional Variation
In addition to differences between the subspecies, recommended habitat areas also differ by region:
State | Recommended Habitat Size |
---|---|
Kansas | ≥ 10,000 acres |
Nebraska | ≥ 25,000 acres |
Oklahoma | ≥ 8,000 acres |
New Mexico | ≥ 2,100 acres |
Colorado | ≥ 44,000 acres |
In Kansas and Oklahoma, recommendations focus on the acreage needed to support stable leks, while estimates are higher in Nebraska and Colorado. The relatively low estimate for New Mexico reflects habitat limitations in the arid shortgrass prairie landscape there. These differences demonstrate the importance of region-specific research to account for local conditions.
Current Status of Habitat
Given the habitat area requirements discussed above, how much prairie-chicken habitat currently remains? Unfortunately, only a fraction of the historically expansive prairie grasslands still exists.
Across the five main greater prairie-chicken states, it is estimated that only about 2-4% of native tallgrass prairie habitat persists in fragmented parcels. For lesser prairie-chickens, less than 5% of intact shinnery oak and sand sagebrush prairie remains in the southern Great Plains. Although total acreage of prairie habitat remaining may be sufficient, it is highly fragmented rather than arranged in large contiguous blocks.
Due to this extreme fragmentation, most remaining prairie-chicken populations are small and isolated. A majority of the birds occupy tracts of rangeland and conservation lands substantially smaller than the 25,000+ acre habitat blocks recommended by research. With prairie acreage continuing to be lost to agriculture, development, and energy extraction, there is a pressing need to protect increasingly large and connected prairie landscapes.
Importance of Large Habitat Blocks
Why are large, unfragmented habitat blocks so critical for prairie-chickens compared to smaller patches? There are several reasons:
Sustaining Leks
Male prairie-chickens gather at traditional lek sites each spring for breeding. Disruption of lek sites can permanently prevent mating in an area. Leks require open visibility and are highly sensitive to habitat fragmentation. Research shows lek occupancy declines when grasslands are broken into smaller blocks, likely due to impaired lek function. Large habitat blocks better sustain intact leks.
Nesting and Brood-Rearing
After mating on leks, female prairie-chickens move into surrounding habitat to nest and raise broods. Nest success is strongly linked to grassland patch size. One Kansas study found nest failure was 1.5 times higher in small versus large prairie fragments, with predation the main cause. Similarly, hen success raising broods improves in larger habitat blocks where chick mortality is lower.
ForagingHabitat
Prairie-chickens have diverse seasonal habitat needs, shifting their movements and diet throughout the year. Large prairie expanses provide more diverse food resources through the seasonal round. Smaller fragments lack this habitat heterogeneity. Fragmentation also increases foraging difficulty by creating risky travel between patches.
Population Connectivity
With birds confined to smaller pieces of prairie, local populations become isolated. This prevents the exchange of individuals between groups that is vital for maintaining genetic diversity. Corridors of habitat connecting fragments allow for increased movement between populations. Large contiguous blocks provide built-in connectivity.
Reduced Predation
Habitat edges and smaller patches tend to concentrate nest predators like coyotes, skunks, raccoons and ravens. Increased predator densities in fragmented landscapes threaten nests and adults. Predation pressure is reduced in expansive grasslands simply because fewer edges exist relative to the interior habitat area.
Resilience to Environmental Variation
Prairie-chickens are vulnerable to seasonal conditions like drought or severe winters. Groups confined to small habitat blocks have less resilience to these stressors compared to metapopulations distributed across large landscapes. Connected populations can rebound from local declines by dispersing to fill vacancies.
Management Implications
Given the habitat area requirements summarized here, what are the implications for prairie-chicken conservation?
– Larger intact prairie blocks are optimal, but complexes of smaller habitat patches may also support populations when sufficiently clustered.
– Habitat corridors should be protected to improve connectivity between isolated fragments.
– Restoring degraded cropland or marginal land to prairie habitat can expand block size.
– Habitat improvements should focus on enlarging and buffering the highest quality areas first.
– Prevent further fragmentation of large remaining prairies from development, roads, fences or energy infrastructure.
– Where habitat is highly fragmented, translocation may be needed to sustain populations.
– Monitoring populations in fragmented landscapes can identify minimum viable patch sizes.
With cooperative effort between government agencies, landowners, industry and conservation groups, it is possible to conserve and expand tracts of quality prairie-chicken habitat. Maintaining connectivity will also become increasingly important under climate change as populations shift their ranges. By using the habitat size guidelines provided by research, biologists can work to ensure that adequate prairie remains to conserve these iconic grassland birds into the future.
Conclusion
Prairie-chickens once numbered in the millions across the expansive prairies of central North America. But extensive habitat loss over the past two centuries has decimated their populations. These birds require large, unfragmented grasslands to sustain viable breeding groups.
Research recommends habitat block sizes from 10,000 acres up to 60,000 acres depending on the prairie-chicken subspecies and geographic region. Larger habitat patches are optimal to support successful lekking, nesting, brood-rearing and foraging. They also reduce predation risks, allow for population connectivity, and confer resilience.
Unfortunately, less than 5% of native prairie currently remains for prairie-chickens, now confined to small isolated fragments. Protecting increasingly larger pieces of intact prairie will be key for their continued survival. This highlights the urgent need for cooperative conservation partnerships across remaining prairie landscapes. By using science-based habitat guidelines, focused effort can still recover prairie-chicken populations and conserve these birds for future generations.