WALDOBORO — When the sun’s heat warms the landscape to the proper degree and its rays provide enough daylight to the forest, monarch butterflies will begin a northward migration so extensive that no individual will complete the full journey and return to the overwintering grounds.

During this trek, they will feed on nectar and reproduce, creating multiple generations by the time fall arrives. As they travel, many people will be watching and anticipating their arrival. I will be among those scanning the flowers for delicate visitors.

The migration begins with the adults from the prior year. While trekking north, the monarchs lay their eggs near the tops of milkweed plants. Underneath leaves, tiny eggs hatch into striped caterpillars.

The young will munch on the leaves of the milkweed and store toxins from the plant, which will serve as protection against hungry predators. These larval caterpillars will grow and feast for up to 14 days before forming a chrysalis and transforming into butterflies. New adults will continue north, laying their own eggs along the way.

It is the butterflies that I typically watch for in my Belfast back yard or during a picnic adventure. The characteristic black and orange wings contrast against the brightly colored blooms of nectar-producing flowers. However, in recent years, this conspicuous garden visitor has become harder and harder to spot because there are simply fewer to find.

The population decline has been many years in the making and is the result of no one factor.

First, the human vendetta against weeds has led to a reduced amount of milkweed for egg laying. Once plentiful in fields and along roadsides, this native plant has been expelled in favor of crops or more colorful blooms. Unfortunately, monarchs cannot effectively reproduce without it.

 Second, the weather has provided challenges. In the past few years, storms and drought have reduced available nectar and water sources during the monarchs’ migration.

For those that reached the overwintering habitat, wet winter storms made it difficult for butterflies to survive the cold. This past winter, researchers recorded the lowest monarch population since the census began in 1993.

As the butterflies return this year, observers across the country are poised to record their numbers. Monarch females can lay 700 eggs in less than one month, so one favorable season would do much to restore the population.

During the summer, when the species spans the U.S. and north into Canada, it is nearly impossible for researchers to count them. However, with the help of citizen scientists throughout the range, it is possible to estimate their path and population. Each piece of collected information leads to a more complete understanding and better management practices.

Though the population has been in decline for multiple seasons, there is hope for a rebound, and citizen scientists may be among the first to record it.

It is with a spirit of optimism that I grab my notebook and pencil to hike about town. I have located patches of milkweed around the post office and near the waterfront park in Belfast.

By now, many in the second generation have hatched and developed into adult form. A third generation is being laid. It is an active time for the butterflies and an important time to keep a record.

Indeed, citizens from the University of Maine Cooperative Extension’s local phenology program, Signs of the Seasons, have been recording monarch sightings for several years now, along with many other species of animals and plants.

Learning to identify and count organisms is a simple way to become part of the effort to learn as much as possible about this native species. It requires very little training and a limited time commitment, but allows citizens to be active participants in a scientific endeavor.

Throughout the country, citizen scientists are creating snapshots in the form of observations. Compiled in a national database, these observations tell a story that researchers alone would not be able to fully capture.

So, by the light of a warm afternoon sun, I settle in with my notebook on a patch of grass. My eyes inspect the pink blossoms of a milkweed patch. I wait and watch for monarchs.

— Special to the Press Herald