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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules
Future Population Trends Several estimates of lesser prairiechicken population growth rates have been based on current conditions for the lesser prairie-chicken, with most derived from demographic matrix models Fields 2004, pp. 7683; Hagen et al. 2009, entire; Sullins 2017, entire;
Cummings et al. 2017, entire. Most studies project declining lesser prairiechicken populations; however, the magnitude of actual future declines is unlikely to be as low as some modeling tools indicate Service 2021, Table 4.10.
Most positive population growth calculations were derived from 2014
2016 Hagen et al. 2017, Supplemental Information; Service 2021, Table 4.10, where estimates indicated populations have increased. However, we caution that any analysis using growth rates based upon short-term data sets can be problematic as they are very sensitive to the starting and ending points in the estimates. Additionally, these growth rates are accompanied by relatively large margins of error.
Estimates based on aerial surveys over the past 9 years have indicated a rangewide fluctuating population beginning with an estimated 28,366 90
percent CI: 17,05540,581 individuals in 2012 to an estimated 34,408 90
percent CI: 21,27047,946 individuals in 2020. Included within this timeframe was a population low of 15,397 90
percent CI: 8,14522,406 individuals in 2013. We caution against drawing inferences from point estimates based upon these data due to low detection probabilities of the species leading to large confidence intervals. We also caution that trend analyses from shortterm data sets are highly sensitive to starting and ending population sizes.
For example, if you use 2012, the first year of available rangewide survey data, as the starting point for a trend analysis, it may appear that populations are relatively stable to slightly increasing, but during the years of 20102013, the range of the lesser prairie-chicken experienced a severe drought and thus lesser prairie-chicken populations were at historic lows. If the data existed to perform the same analysis using the starting point as 2009, then the results would likely show a decreasing population trend.
The future risk of extinction of the lesser prairie-chicken has been evaluated using historical ground surveys Garton et al. 2016, pp. 6073.
This analysis used the results of those surveys to project the risk of lesser prairie-chicken quasi-extinction in each of the four ecoregions and rangewide over two timeframes, 30 and 100 years
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into the future. For this analysis, quasiextinction was set at effective population sizes demographic Ne of 50
populations at short-term extinction risk and 500 populations at long-term extinction risk adult breeding birds, corresponding to an index based on minimum males counted at leks of 85
and 852, respectively Garton et al.
2016, pp. 5960. The initial analysis using data collected through 2012 was reported in Garton et al. 2016, pp. 60
73, but it has since been updated to include data collected through 2016
Hagen et al. 2017, entire. We have identified concerns in the past with some of the methodologies and assumptions made in this analysis, and the challenges of these data are noted in Zavaleta and Haukos 2013, p. 545 and Cummings et al. 2017, pp. 2930.
While these concerns remain, this work represents one of the few attempts to project risk to the species across its range, and we considered it as part of our overall analysis and recognize any limitations associated with the analysis.
Results were reported for each analysis assuming each ecoregion is functioning as an independent population and also assuming there is movement of individuals between populations Service 2021, Table 4.11;
Table 4.12. The results suggest a wide range of risks among the ecoregions, but the Sand Sagebrush Ecoregion consistently had the highest risks of quasi-extinction and the Short-Grass/
CRP Ecoregion had the lowest. This analysis was based only on simulating demographic variability of populations and did not incorporate changing environmental conditions related to habitat or climate.
Determination of Lesser Prairie-Chicken Status Section 4 of the Act 16 U.S.C. 1533
and its implementing regulations 50
CFR part 424 set forth the procedures for determining whether a species meets the definition of an endangered species or a threatened species. The Act defines endangered species as a species in danger of extinction throughout all or a significant portion of its range, and threatened species as a species likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. The Act requires that we determine whether a species meets the definition of endangered species or threatened species because of any of the following factors: A The present or threatened destruction, modification, or curtailment of its habitat or range; B
Overutilization for commercial, recreational, scientific, or educational
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purposes; C Disease or predation; D
The inadequacy of existing regulatory mechanisms; or E Other natural or manmade factors affecting its continued existence.
Status of the Southern DPS of the Lesser Prairie-Chicken Throughout All of Its Range We have carefully assessed the best scientific and commercial information available regarding the past, present, and future threats to the Southern DPS
of the lesser prairie-chicken and its habitat. We analyzed effects associated with habitat degradation, loss, and fragmentation, including conversion of grassland to cropland Factor A, petroleum production Factor A, wind energy development and transmission Factor A, woody vegetation encroachment Factor A, and roads and electrical distribution lines Factor A;
other factors, such as livestock grazing Factor A, shrub control and eradication Factor A, collision mortality from fences Factor E, predation Factor C, influence of anthropogenic noise Factor E, and fire Factor A; and extreme weather events Factor E. We also analyzed the effects of existing regulatory mechanisms Factor D and ongoing conservation measures. In the SSA report, we also considered three additional threats:
Hunting and other recreational, educational, and scientific use Factor B; parasites and diseases Factor C;
and insecticides Factor E. We consider all of these impacts now in analyzing the status of the Southern DPS.
Over the past several decades, habitat loss, fragmentation, and degradation have resulted in the loss of large areas of the habitat that supports the lesser prairie-chicken in the Southern DPS.
Suitable habitat has been lost as grasslands are converted to cropland, and as petroleum and natural gas production and wind energy development have resulted in further loss of habitat. The lesser prairiechicken is particularly vulnerable to changes on the landscape, as it requires large blocks of suitable habitat to complete its life-history needs. This includes its lek breeding system, which requires males and females to be able to hear and see each other over relatively wide distances, the need for large patches of habitat that include several types of microhabitats, and the behavioral avoidance of vertical structures. In the case of petroleum and wind energy production, the extent of the impact from the threat is not just the original site, but also all roads, powerlines, and other infrastructure associated with the sites, and noise
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