Danaus plexippus feeding on narrowleaf milkweed, Owens Valley Station. WMRC at Sierra Earth Day 2023 Danaus plexippus feeding on narrowleaf milkweed, Owens Valley Station. Come learn about UC WMRC from center staff at Sierra Earth Day on Saturday, April 22nd from 10 a.m. until 5 p.m. at the Bishop City Park. We will have t-shirts available for sale and some free goodies.