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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules
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TABLE 1RESULTS OF LESSER PRAIRIE-CHICKEN GEOSPATIAL ANALYSIS BY ECOREGION AND RANGEWIDE, ESTIMATING
TOTAL AREA IN ACRES, POTENTIAL USABLE AREA, AND AREA CALCULATED BY OUR NEAREST NEIGHBOR ANALYSIS
All numbers are in acres. Numbers may not sum due to rounding.
Ecoregion total area
Ecoregion
Potential usable area
Nearest neighbor analysis
Percent of total area
Short-Grass/CRP
Mixed-Grass
Sand Sagebrush

6,298,014
8,527,718
3,153,420

2,961,318
6,335,451
1,815,435

1,023,894
994,483
1,028,523

16.3
11.7
32.6

Northern DPS total
Shinnery Oak Southern DPS total

17,979,152
3,850,209

11,112,204
2,626,305

3,046,900
1,023,572

16.9
26.6

Rangewide Totals

21,829,361

13,738,509

4,070,472

18.6

The results of the nearest neighbor analysis indicate that about 19 percent of the entire analysis area and from 12
percent to 33 percent within each of the four ecoregions is available for use by the lesser prairie-chicken. Due to limitations in data availability and accuracy as well as numerous limitations with the methodology and assumptions made for this analysis, this estimate should not be viewed as a precise measure of the lesser prairiechicken habitat; instead, it provides a generalized baseline to characterize the current condition and by which we can then forecast the effect of future changes.
In the SSA report, we also considered trends in populations. Estimates of population abundance prior to the 1960s are indeterminable and rely almost entirely on anecdotal information Boal and Haukos 2016, p.
6. While little is known about precise historical population sizes, the lesser prairie-chicken was reported to be quite common throughout its range in the early 20th century Bent 1932, pp. 280
281, 283; Baker 1953, p. 8; Bailey and Niedrach 1965, p. 51; Sands 1968, p.
454; Fleharty 1995, pp. 3844; Robb and Schroeder 2005, p. 13. In the 1960s, State fish and wildlife agencies began routine lesser prairie-chicken monitoring efforts that have largely continued to today.

In the SSA report and this proposed rule, we discuss lesser prairie-chicken population estimates from two studies.
The first study calculated historical trends in lesser prairie-chicken abundances from 1965 through 2016
based on population reconstruction methods and historical lek surveys Hagen et al. 2017, pp. 69. The results of these estimates indicate that lesser prairie-chicken rangewide abundance based on a minimum estimated number of male lesser prairie-chicken peaked from 19651970 at a mean estimate of about 175,000 males. The mean population estimates maintained levels of greater than 100,000 males until 1989, after which they steadily declined to a low of 25,000 males in 1997 Garton et al. 2016, p. 68. The mean population estimates following 1997 peaked again at about 92,000 males in 2006 but subsequently declined to 34,440 males in 2012. The Service 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 other studies for example, Zavaleta and Haukos 2013, p.
545; Cummings et al. 2017, pp. 2930.
While these concerns remain, including the very low sample sizes particularly in the 1960s, this work represents the only attempt to compile the extensive historical ground lek count data collected by State agencies to estimate rangewide population sizes.

Approximate distribution of lek locations as reported by WAFWA for the entire range that were observed occupied by lesser prairie-chicken at least once between 2015 and 2019 are shown in the SSA report Service 2021, Appendix E, Figure E.7.
Following development of aerial survey methods McRoberts et al. 2011, entire, more statistically rigorous estimates of lesser prairie-chicken abundance both males and females have been conducted by flying aerial line-transect surveys throughout the range of the lesser prairie-chicken and extrapolating densities from the surveyed area to the rest of the range beginning in 2012 Nasman et al. 2020, entire. The aerial survey results from 2012 through 2020 Service 2021, Figure 3.2 estimated the lesser prairie-chicken population abundance, averaged over the most recent 5 years of surveys 20152020, no surveys in 2019, at 27,384 90 percent CI: 15,690, 59,981
Nasman et al. 2020, p. 21; Table 2. The results of these survey efforts should not be taken as precise estimates of the annual lesser prairie-chicken population abundance, as indicated by the large confidence intervals. Thus, the best use of this data is for long-term trend analysis rather than for conclusions based on annual fluctuations. As such, we report the population estimate for the current condition as the average of the past 5 years of surveys.

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TABLE 2RANGEWIDE AND ECOREGIONAL ESTIMATED LESSER PRAIRIE-CHICKEN TOTAL POPULATION SIZES AVERAGED
FROM 2015 TO 2020, LOWER AND UPPER 90 PERCENT CONFIDENCE INTERVALS CI OVER THE 5 YEARS OF ESTIMATES, AND PERCENT OF RANGEWIDE TOTALS FOR EACH ECOREGION FROM NASMAN et al. 2020, P. 21. NO SURVEYS WERE CONDUCTED IN 2019
5-Year average estimate
Ecoregion Short-Grass/CRP
Mixed-Grass
Sand Sagebrush
Shinnery Oak

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16,957
6,135
1,215
3,077

5-Year minimum lower CI
13,605
1,719
196
170

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5-Year maximum upper CI
35,350
11,847
4,547
8,237

Percent of total 62
22
4 11