Pollinator Habitat Conservation Along Roadways, Volume 7: Inland Northwest (2023)

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3-1 Chapter 3 Imperiled Pollinator Profiles The Inland Northwest, which includes parts of Oregon, Washington, Idaho, and Nevada, is home to a diverse assemblage of pollinators (Figure 1-1). In this region, there is one candidate species for listing under the federal Endangered Species Act (ESA) as of March 2022. However, there are many imperiled pollinators in this region that are not protected by the ESA. This section provides profiles of ESA-listed and -candidate pollinator species found in the Inland Northwest, as well as imperiled pollinators that have the potential to be listed in the future based on NatureServe rankings and expert opinion (Table 3-1). The profiles of imperiled species not listed under the ESA include three imperiled bumble bees. This is not an exhaustive list of all declining pollinators in the region; the focus is on species in need of conservation that have a broad distribution and those that are more likely to affect Departments of Transportation (DOTs). An overview of the basic biology of bees, butterflies, and other insect pollinators can be found in Chapter 2. This section presents information on life history, distribution, threats, and habitat requirements for imperiled pollinators in this region. Information on known adult flight times (i.e., the breeding period) and larval active times (for butterflies and moths; larval bees live within nests) are included. The profiles also include a list of important plants that are used by each species as host plants or for pollen and/or nectar. Some of these plants are nonnative species or noxious weeds. These species are included in the profiles, as the information may be useful, but using them in revegetation efforts is not recommended (see Chapter 7 for more). Some basic conservation recommendations and information on the effects of roadside management on each species are also provided, when such information is available. Insects generally tend to be less well studied than vertebrates; therefore, very little is known about the biology and habitat requirements of some of these species. Other pollinator species may be better studied, but rigorous studies of the effects of different management practices on the species or their habitat may still be lacking. The best possible recommendations are made based on the available information. The profiles provide information on life cycles, host plants, habitat needs, and adult flight times that can be used to tailor maintenance and revegetation decisions (Chapters 6 and 7). General active times for adults and larvae are also provided. It should be noted that active times may shift regionally, such as with elevation or latitude, or from year to year with changes in climate. However, consultation with local experts, as well as biologists from state and federal agencies, is recommended to help DOTs develop meaningful management plans for species of interest in their areas because these profiles cannot capture the site- specific nuances that should be considered. As the profiles indicate, habitat loss is a primary driver of species’ declines. Roads can be a cause of habitat fragmentation (Box 5-3). However, with investments in high-quality revegetation (revegetation that prioritizes usage of native plants and high plant diversity, including an abundance of flowering plants that provide pollen and nectar or act as host plants for butterflies) where appropriate, roadsides can also provide an ideal opportunity to increase habitat connectivity for many species, including pollinators. It is important to note that although some of the species profiled in this chapter may be unlikely to use

Chapter 3. Imperiled Pollinator Profiles  3-2 roadside habitat for breeding, individuals may still use roadside habitat for nectar or pollen or as movement corridors. Therefore, it is worthwhile to invest in high-quality habitat restoration projects along roadsides near natural areas, preserves, and populations of imperiled species. Another common threat to many imperiled butterflies in the United States is noxious and invasive plants that displace required host plants. Here again, investing in high-quality habitat restoration using native plants can benefit imperiled pollinators, even if those pollinators are not using roadside habitat, by helping to slow the spread of invasive plants into key habitat areas. This section includes profiles of pollinator species that may not occur in roadside habitat, but may be found in other DOT land holdings, such as mitigation areas (Table 3-1). Table 3-1. List of profiled imperiled pollinator species in the Northern Plains region. Scientific Name  Common Name  Status#  ESA‐Listed Pollinator Species  Danaus plexippus  Monarch butterfly  Candidate  Declining Pollinator Species  Bombus morrisoni  Morrison’s bumble bee  G3  Bombus occidentalis*  Western bumble bee  G3  Bombus suckleyi*  Suckley’s cuckoo bumble bee  G2G3  * Species under review or are on the U.S. Fish and Wildlife Service workplan to be evaluated for listing under the ESA as of March 2022. # Status of pollinators is either the ESA status for listed species or is taken from NatureServe (accessed  March 2022) for species not listed under the ESA.    G1: Critically Imperiled. At very high risk of extinction due to extreme rarity (often five or fewer populations), very steep declines, or other factors.  G2: Imperiled. At high risk of extinction due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.  G3: Vulnerable. At moderate risk of extinction due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors.  G4: Apparently Secure. Uncommon but not rare; some cause for long‐term concern due to declines or other factors.  G5: Secure. Common; widespread and abundant.  G#G#: Range Rank. A numeric range rank (e.g., G2G3) is used to indicate the range of uncertainty in the status of a species or community.  T#: Infraspecific Taxon (for subspecies or varieties). The status of infraspecific taxa is indicated by a “T‐ rank” following the species’ global rank. For example, the global rank of a critically imperiled subspecies of an otherwise widespread and common species would be G5T1.

Chapter 3. Imperiled Pollinator Profiles  3-3 3.1 Monarch Butterfly (Danaus plexippus)  Jan  Feb  Mar  April  May  June  July  Aug  Sept  Oct  Nov  Dec  Adult  Larvae  Adult monarch (top left) and monarch distribution within the U.S. (top right). Adult flight times (i.e.,  breeding period; blue) and larvae active periods (green) for monarchs in this region are shown in the chart  (bottom). Adult and larval active times vary regionally; see Figure 3‐1 for regionally specific suggested  management windows. Photo credit: Stephanie McKnight/The Xerces Society.  Order: Lepidoptera Family: Nymphalidae Status: Candidate Distribution: As of 150 years ago, the monarch was restricted to southern Canada, the lower 48 states, Mexico, Central America, and northwestern South America. In recent years the species has spread or been introduced to other areas including Spain, Hawaii, Australia, and New Zealand. Where it occurs: During the breeding season, monarchs can be found in terrestrial habitats throughout the western United States, but they tend to avoid dense forest. How to recognize: Orange and black monarchs are larger than most butterflies with similar coloration. In contrast to the species that most closely resembles monarchs— viceroys—monarchs lack the black line crossing the middle of each hind wing. Behaviorally, monarchs tend to glide more than most other butterfly species. Life cycle: Western monarchs generally breed west of the Rocky Mountains and overwinter along the Pacific coast. However, there is some mixing between the western and eastern populations (which breed east of the Rocky Mountains and overwinter in central Mexico), with some western monarchs migrating to central Mexico. Monarchs have several generations a year, which spread out and move north and west from the overwintering sites. Adults and larvae can be found in the West throughout the breeding season. In the Inland Northwest, monarch breeding season typically occurs from mid-May through the end of September (Figure 3-1). In the fall, adult monarchs enter reproductive diapause and return to overwintering sites along the California coast. Those individuals leave the overwintering grounds in Monarch butterfly larvae  Photo Credit: Ray Moranz/The Xerces  Society 

Chapter 3. Imperiled Pollinator Profiles  3-4 spring to lay eggs on milkweeds, the larval host plant. While larvae specialize on milkweed, adults use a variety of plants for nectar (Table 3-2). Habitat needs: Although monarchs tend to avoid dense forests, they use most terrestrial and wetland ecosystems for breeding and migration, as long as those ecosystems have milkweeds and nectar sources. This includes roadsides: monarchs lay eggs on a variety of milkweed species on roadsides and in roadside ditches. Top reasons for decline, if known: Loss and degradation of overwintering and breeding habitat; loss of habitat via conversion to row-crop agriculture and urban development; use of herbicides that kill milkweeds and nectar sources; use of insecticides that kill monarchs or cause negative but sublethal effects. General conservation recommendations: Protect and restore breeding habitat in this region; this includes planting of native milkweed and nectar plants. The Snake River basin has been identified as an especially important part of this region for monarch conservation efforts. Reduced use of pesticides will benefit the conservation of this species. Roadside management recommendations: Mowing during the breeding season (mid-May through the end of September) will likely kill many monarch eggs, larvae and pupae. Spraying of herbicides may kill milkweed and nectar plants. Table 3-2. Plants used by western monarchs. Species Name  Common Name  Notes  Larval Host Plants  Asclepias cordifolia  Heartleaf milkweed  Likes rocky soils  Asclepias fascicularis  Narrow‐leaved milkweed Asclepias speciosa  Showy milkweed Asclepias cryptoceras  Pallid milkweed Asclepias incarnata  Swamp milkweed Nectar Plants  Cirsium occidentale  Cobwebby thistle Cleome lutea  Yellow spiderflower Eriogonum umbellatum  Sulphur‐flower buckwheat Euthamia occidentalis  Western goldentop Monardella odoratissima  Mountain monardella Gaillardia aristata  Blanketflower Rudbeckia occidentalis  Western coneflower Solidago spp.  Goldenrod

Chapter 3. Imperiled Pollinator Profiles  3-5 Taken from handout created by Monarch Joint Venture and The Xerces Society:  https://monarchjointventure.org/images/uploads/documents/MowingForMonarchsUpdated.pdf.  Figure 3-1. Management timing windows for monarchs in the United States. Roadside milkweed guides:  Milkweeds of ID, OR, and WA: https://xerces.org/publications/fact-sheets/roadside- habitat-for-monarchs-milkweeds-of-id-or-wa  Milkweeds of NV and UT: https://xerces.org/publications/fact-sheets/roadside- habitat-for-monarchs-milkweeds-of-nv-ut 3.1.1 References Dilts, T. E., M. O. Steele, J. D. Engler, E. M. Pelton, S. J. Jepsen, S. J. McKnight, A. R. Taylor, C. E. Fallon, S. H. Black, E. E. Cruz, D. R. Craver, and M. L. Forister. 2019. “Host Plants and Climate Structure Habitat Associations of the Western Monarch Butterfly.” Frontiers in Ecology and Evolution 7:188. Espeset, A. E., J. G. Harrison, A. M. Shapiro, C. C. Nice, J. H. Thorne, D. P. Waetjen, J. A. Fordyce, and M. L. Forister. 2016. “Understanding a migratory species in a changing world: climatic effects and demographic declines in the western monarch revealed by four decades of intensive monitoring.” Oecologia 181(3):819–830.

Chapter 3. Imperiled Pollinator Profiles  3-6 Pelton, E. M., C. B. Schultz, S. J. Jepsen, S. H. Black, and E. E. Crone. 2019. “Western Monarch Population Plummets: Status, Probable Causes, and Recommended Conservation Actions.” Frontiers in Ecology and Evolution 7:258. Satterfield, D. A., F. X. Villablanca, J. C. Maerz, and S. Altizer. 2016. “Migratory monarchs wintering in California experience low infection risk compared to monarchs breeding year-round on non-native milkweed.” Integrative and Comparative Biology 56(2):343– 352. Schultz, C. B., L. M. Brown, E. Pelton, and E. E. Crone. 2017. “Citizen science monitoring demonstrates dramatic declines of monarch butterflies in western North America.” Biological Conservation 214:343–346. The Xerces Society. 2018. Managing for monarchs in the west: best management practices for conserving the monarch butterfly and its habitat. The Xerces Society for Invertebrate Conservation, Portland, OR. Available: www.xerces.org. Waterbury, B., A. Potter, and L. K. Svancara. 2019. “Monarch Butterfly Distribution and Breeding Ecology in Idaho and Washington.” Frontiers in Ecology and Evolution 7:172. 3.2 Bumble Bees: Morrison’s Bumble Bee (Bombus  morrisoni), Western Bumble Bee (B. occidentalis),  Suckley’s Cuckoo Bumble Bee (B. suckleyi)  Order: Hymenoptera Family: Apidae Habitat Needs: Availability of food and nesting resources are key features in determining the success of a bumble bee colony. It is critical to maintain a bloom of floral resources throughout the spring, summer, and fall to supply bumble bees with a diversity and abundance of pollen and nectar, food for adults and larvae. Bumble bees nest above, on, or under the ground, utilizing pre-existing insulated cavities such as rock piles, areas of dense vegetation (e.g., bunch grasses), or old bird nests or mouse burrows. See Table 3-3 for a list of plants used by bumble bees. Top reasons for decline, if known: There are multiple factors affecting bumble bee decline including habitat loss, pesticide exposure, climate change, pathogens, and parasites, as well as the introduction of nonnative bee species. General conservation recommendations: Preserve, restore, and create high-quality habitat that includes suitable nesting, foraging, and overwintering sites throughout a species’ range. Assess and mitigate risk of pesticide use in or near suitable habitat to avoid treating flowers in bloom or contaminating nesting and overwintering sites. Avoid the introduction of managed honey bees and managed bumble bees to areas of natural habitat to protect and minimize disease exposure. Roadside management recommendations: Intensive mowing may deplete floral resources and potentially disturb species that have nested above ground in the roadside. Reduced mowing frequency would alleviate this problem. In areas with above-ground nesting species, avoid mowing during the nesting season to avoid harming nests. Use a diversity of plants in revegetation to ensure multiple species are in bloom from spring

Chapter 3. Imperiled Pollinator Profiles  3-7 through fall. Blanket spraying of herbicides can affect the health of bumble bees in the area by reducing floral resources. A recent study of roadside mortality of bumble bee queens in Sweden found that bumble bee queens used roadsides with both high plant diversity and low plant diversity in similar proportions when looking for nests. Queen mortality increased with traffic volume but was slightly lower along roadsides with higher quality vegetation. The authors recommend improving habitat quality along roadsides, and keeping a mown buffer strip next to the road to reduce queen mortality. 3.2.1 Morrison’s Bumble Bee (Bombus morrisoni)   Jan  Feb  Mar  April  May  June  July  Aug  Sept  Oct  Nov  Dec  Adult                                                                                                Adult Morrison’s bumble bee (top left) and known state‐level distribution in the U.S. (top right). Adult  flight times (i.e., breeding period) are shown in the chart (bottom). Photo credit: Leif Richardson/The  Xerces Society.    Status: Vulnerable (G3) Distribution: Mountain and desert West Where it occurs: Dry shrubland Parasite of: In Alaska, likely parasite of Western bumble bee (B. occidentalis) and cryptic bumble bee (B. cryptarum). Flight Time: This species is typically active on the landscape from early May through mid October. Between November and April, queens are overwintering in the ground. Nesting behavior: Nests underground. How to recognize: This bumble bee has black hair on the front of the face and yellow hair on the top of the head. The thorax is predominantly yellow, and black on the side. On the abdomen, segments one and two are yellow, segment three has some yellow, and segments four to six are black. Males may have different color patterns. Body size: Large. Queens range from 22 to 26 millimeters (0.87 to 1.02 inches) and workers range from 12 to 22 millimeters (0.47 to 0.87 inch).

Chapter 3. Imperiled Pollinator Profiles  3-8 3.2.2 Western Bumble Bee (Bombus occidentalis)   Jan  Feb  Mar  April  May  June  July  Aug  Sept  Oct  Nov  Dec  Adult                                                                                                Adult western bumble bee (top left) and known U.S. state‐level distribution (top right). Adult flight times  (i.e., breeding period) are shown in the chart (bottom). Photo credit: Rich Hatfield.    Status: Vulnerable (G3), under review; petitioned in 2018 to be listed as endangered under the California Endangered Species Act; petitioned in 2015 to be listed as endangered or threatened under the ESA Distribution: Western United States from the coast to mountain meadows out to the northwestern Great Plains. Population has shown sharp decline since the late 1990s west of the Sierra-Cascade ranges . Where it occurs: Urban, shrubland, grassland Flight Time: This species is typically active on the landscape from May through September). Between October and April, queens are overwintering in the ground. Nesting behavior: Usually nests underground. How to recognize: This bumble bee has mixed black and yellow hair on the face. The thorax has a yellow band in front of the wings and a black band or spot between the wings; behind the wings can be black, yellow, or mixed. Segment one of the abdomen is black, segments two and three are black or have some yellow, segments four and five are white or pale yellow, and segment six is black. Males may have different color patterns. Body size: Medium. Queens range from 20 to 21 millimeters (0.77 to 0.84 inch) and workers range from 9 to 15 millimeters (0.36 to 0.59 inch).

Chapter 3. Imperiled Pollinator Profiles  3-9 3.2.3 Suckley’s Cuckoo Bumble Bee (Bombus suckleyi)   Jan  Feb  Mar  April  May  June  July  Aug  Sept  Oct  Nov  Dec  Adult                                                                                               Adult Suckley’s cuckoo bumble bee (top left) and known U.S. state‐level distribution (top right). Adult flight  times (i.e., breeding period) are shown in the chart (bottom). Photo credit: Cory Sheffield.    Status: Imperiled to vulnerable (G2G3); under review for listing under the ESA Distribution: Mountain west and north into Canada Where it occurs: Forest, grassland, shrubland Parasite of: Western bumble bee (B. occidentalis) Flight Times: This species is typically active on the landscape in June and again in early to mid August. During the peak of summer, this species remains in the host’s nest. Nesting behavior: Parasite of western bumble bee, which nests underground. How to recognize: This bumble bee has black hair on the face and a predominantly yellow thorax with a black stripe between the wings. The abdomen is predominantly black with a yellow band toward the posterior end interrupted medially. Males may have different color patterns. Body size: Medium. Females range from 18 to 23 millimeters (0.72 to 0.92 inch). Table 3-3. Plants used by bumble bees. Species Name By Bloom  Period  Common Name  Notes   Early  Balsamorhiza sagittata  Arrowleaf balsamroot  Yellow; perennial  Lupinus polyphyllus  Bigleaf lupine  Purple; perennial 

Chapter 3. Imperiled Pollinator Profiles  3-10 Species Name By Bloom  Period  Common Name  Notes   Prunella vulgaris ssp.  lanceolata  Lance selfheal  Purple; perennial  Rosa woodsii  Western wild rose/Wood’s  rose  Pink; perennial  Mid  Asclepias speciosa  Showy milkweed  Pink; perennial  Lupinus argenteus  Silvery lupine  White/blue/purple; perennial  Monardella odoratissima  Mountain monardella/coyote  mint  White/blue/purple; perennial  Late  Agastache urticifolia  Nettle leaf horsemint  White/pink; perennial  Chamerion angustifolium  Fireweed  Pink; perennial  Solidago canadensis  Canada goldenrod  Yellow; perennial  Symphyotrichum eatonii  Eaton’s aster  White/purple; perennial  3.2.4 References Dániel-Ferreira, J., Å. Berggren, R. Bommarco, J. Wissman, and E. Öckinger. 2022. Bumblebee queen mortality along roads increase with traffic. Biological conservation 272:109643. Hatfield, R., S. Jepsen, E. Mader, S. H. Black, and M. Shepherd. 2012. Conserving bumble bees. Guidelines for Creating and Managing Habitat for America's Declining Pollinators. The Xerces Society for Invertebrate Conservation, Portland, OR. Williams, P. H., R. W. Thorp, L. L. Richardson, and S. R. Colla. 2014. Bumble Bees of North America: An Identification Guide. Princeton University Press, Princeton, NJ. doi:10.2307/j.ctt6wpzr9.