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Federal Register / Vol. 86, No. 85 / Wednesday, May 5, 2021 / Proposed Rules Boxthorn habitat is still considered high-quality habitat, although moderate to high population densities are also found in sagebrush and shrub habitat near canyons and along the steep eastern slope. SC Bells sparrows are present in significantly lower densities in mixed shrub, cactus, and grassland grass/herb habitats along the central plateau Meiman et al. 2018, p. 18. The west shore boxthorn habitat, where the species was originally described, remains densely occupied and is thus important to the species.
SC Bells sparrows inhabit most plant communities on SCI, including Maritime Desert Scrub in Lycium boxthorn phase, Opuntia prickly pear phase, and Cylindropuntia cholla phase; Maritime sage scrub; canyon shrubland/woodland; and grasslands USFWS 2020a, pp. 2021. Within these plant communities, SC Bells sparrows show an affinity for areas dominated by shrubs and cacti Opuntia spp.. SC Bells sparrows demonstrate a positive association with structural shrub cover Meiman et al. 2015a, p.
33, as they typically use shrubs for nesting substrate and use the gaps between and area underneath shrubs for foraging. The abundance of shrubs, including boxthorn, has been positively correlated with sparrow density Turner 2009, pp. 5354. High grass cover has been correlated with lower sparrow densities and larger territory sizes, which may indicate that grasses are not likely important resources during the nesting season Turner 2009, pp. 5354.
The SC Bells sparrow is a ground gleaner and eats available insects and spiders, and also seeds taken from the ground and low vegetation. During the winter, SC Bells sparrows feed on prickly pear and cholla cactus fruit and on moths Hyde 1985, p. 24. The initiation of breeding activity and the length of the nesting season appear to be tied to precipitation patterns Kaiser et al. 2007, pp. 4849; Meiman et al. 2018, p. 36. Breeding activity usually peaks in March and April, and lasts through late June or July. Clutch size ranges from 1 to 5 eggs, with asynchronous hatching after 12 to 13 days of incubation conducted mostly by the female Martin and Carlson 1998, p. 9. SC Bells sparrows are able to breed their first year, and multiple clutches per year have been recorded, with most pairs producing multiple successful broods in favorable years Martin and Carlson
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1998, p. 9; Kaiser et al. 2008, p. 36. SC
Bells sparrows express site fidelity each nesting season, and juveniles disperse from the natal area during their first winter.
Amounts and distribution of rainfall affect the timing and extent of vegetation growth and flowering. During drought years, SC Bells sparrows may not reproduce at all or a subset of the population may suppress breeding Kaiser et al. 2007, p. iv; Stahl et al.
2010, p. 48; Meiman et al. 2019, p. 35, which can, but does not always, result in depressed populations following drought years. SC Bells sparrows appear to respond to favorable precipitation patterns and resulting conditions by producing multiple clutches, which typically drive population numbers up in years that follow good precipitation years Kaiser et al. 2007, p. iv; Stahl et al.
2010, p. 50. However, while there is a relationship between reproductive output and rainfall, the impacts of droughts of varying duration and severity on the population are unclear, and the mechanisms driving these relationships are unknown USFWS
2020a, pp. 5863.
San Clemente Island Bush-Mallow A thorough review of the taxonomy, life history, and ecology of the San Clemente Island bush-mallow is presented in the SSA report USFWS
2020b. San Clemente Island bushmallow Malacothamnus clementinus is a rounded shrub in the Malvaceae mallow family Slotta 2012; 77 FR
29078, May 16, 2012, p. 29080. Plants are generally 2.3 to 3.3 ft 0.7 to 1 m tall with numerous hairy branched stems arising from the base of the plant Munz and Johnston 1924, p. 296; Munz 1959, pp. 122125; Bates 1993, p. 752.
Flowers are clustered in the uppermost leaf axils, forming interrupted spikes 3.9
to 7.9 in 10 to 20 cm long Munz 1959, p. 125. Flowers are bisexual and variously described as having pink or white and fading lavender petals Munz and Johnston 1924, p. 296; Bates 1993, p. 752.
The historical range and distribution of SCI bush-mallow on SCI is unknown because botanical studies were not conducted on the island prior to the introduction of ungulates beginning in the 1800s Kellogg and Kellogg 1994, p.
4. At the time of listing, one site at Lemon Tank Canyon on the eastern side
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of the island and two additional locations of two to three small plants in China Canyon on the southern end of the island were known 42 FR 40682, August 11, 1977, p. 40683; USFWS
1984, p. 48. Since listing, new locations of SCI bush-mallow have been discovered among the generally southwesterly facing coastal terraces and their associated escarpments in the southern and middle regions of SCI
Junak and Wilken 1998, pp. 1416, Geographic Information System GIS
data; Junak 2006, pp. 1176, GIS data;
Tierra Data Inc. 2008, pp. 124, appendices and GIS data; San Diego State University Soil Ecology and Restoration Group SERG 2010a and 2010b, GIS data. Most of the known locations occur throughout the southwestern region of the island. The main southern distribution of SCI bushmallow is disconnected from the Lemon Tank Canyon locality by approximately 4 mi 6.4 km. Many of these new locations have been documented since feral mammals were removed, suggesting that plants may have reemerged from underground stems that survived grazing by feral herbivores Junak 2006, pers. comm. in 77 FR
29078, May 16, 2012, p. 29086, although experts doubt that rhizomes would be able to store enough energy to sprout after a long period of dormancy without sending up shoots in the interim Munson 2019, pers. comm.;
Rebman 2019, pers. comm.; Morse 2020, pers. comm..
The current abundance and distribution of SCI bush-mallow is estimated to total approximately 5,611
individuals at 222 locations occupying 15 watersheds see Figure 2, below USFWS 2020b, pp. 2931. Because distinguishing genetically distinct individuals among groups of stems is difficult, counts or estimates of individuals have most often been used collectively to refer to both genetically distinct individuals genets and clones ramets USFWS 2020b, p. 26. In the current estimate, individuals refer to individual plants and not necessarily to genetically distinct individuals. Because of access restrictions due to risk of unexploded ordnances, occurrences within areas subject to bombardment have not been assessed recently enough to be included in this estimate, but are likely still extant.

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