The information in this state update was provided by Dr. David James, firstname.lastname@example.org. Please contact him for additional information about the update.
Washington State is usually the final destination for the majority of western monarchs migrating north in spring. A few make it into British Columbia by up to 100 miles but many make Washington their summer-breeding home in most years. Most abundance occurs on the eastern side of the state although a few migrate north through western Washington and will stop and lay eggs if they encounter milkweed.
Showy milkweed is the dominant milkweed species in Washington and it is common to abundant along roadsides and in riparian areas of eastern Washington. The first monarchs are seen in early June each year in Washington and produce at least two generations. Monarchs eclosing in August may join the migrating generation and those eclosing in September certainly do.
By early October, most monarchs have left Washington State and are en route or have arrived at overwintering sites in California. A few individuals migrate in a different direction towards the south-east, through Utah and may end up overwintering in Mexico.
After three years with only a handful of monarch sightings in Washington, we are expecting a significant turnaround in 2022. This is because of the tremendous numbers of overwintering monarchs recorded in California in 2021/22. If overwintering concludes in California without severe storms, prospects are good for development of a sizeable spring migrant population in May-June. This population should be much larger than in recent years and we expect a significant incursion of migrating monarchs into Washington during the first half of June. So, for the first time since 2018, we should see breeding populations of monarchs in eastern WA, and migrants should also be sighted in western WA during June as they head north.
The monarch is an adaptable and surprising creature and has definitely surprised many people by its stunning population resurgence during 2021. From a dismal low population of just 1899 butterflies overwintering along the California coast during 2020/21, the monarch has rebounded to produce an overwintering population of more than 247,000 in 2021/22. Hopefully, the population will sustain this population increase in 2022 and perhaps increase it, so that overwintering numbers are comparable or greater in 2022/23.
Normally, the first monarchs arrive in southern Washington during the first week of June. They did this without fail from 2004-2017. The abundant stands of Showy Milkweed in eastern Washington then support at least two generations of caterpillars before the population migrates south during September.
All of us in Washington hope the annual summer visit by monarchs to our state will continue and increase further in the future. However, for this to happen, we need to work on the restoration of milkweed and monarchs in California, the hub of monarch ecology in the west, as well as throughout the western US. We also need to minimize our use of pesticides in agricultural and urban areas.
Abundant Showy milkweed at a central Washington monarch breeding site that went unused in 2020.
Hands used for crime now nurturing a struggling species (KXLY News, September, 2018)
Monarch Butterflies in the Pacific Northwest Facebook page