Outdoor Encounters

By Nathan Bolls on August 31, 2016

Most birds soon will be pumping up for migration. Some of their journeys are legend, but perhaps none so much as for the delicate monarch butterfly.

This marvelous animal weighs less than one gram, of which it takes 28.35 to make an ounce. By contrast, an adult ruby-throated hummingbird weighs about 3.2 grams. The monarch's bird-like annual migration to one small mountainous area in central Mexico (and back again) is unique in the insect world and especially remarkable because the insects have no elders to show them the way.

An understanding of this migration pattern has come from observations and from tagged individuals. Students of monarch migration speak of four (sometimes five) generations to complete one migration cycle. Let's begin with those that have flown 2-3,000 miles from the USA or southern Canada to overwinter in Mexico from December through February. Then, in March, these monarchs begin heading north, stopping in the southern USA (usually Texas) to breed and lay eggs. From egg to butterfly takes about four weeks.

This first generation, born in south, then moves farther north throughout the USA and southern Canada (east of the Continental Divide). They breed and lay eggs. The resulting second generation, born in north, breeds and lays eggs in the north. The resulting third generation, born in north, also breeds and lays eggs in north. The resulting fourth generation, born in north, migrates to and overwinters in Mexico. The literature states that monarchs can travel 50-100 miles per day (especially with a favorable wind) and take up to two months to make the journey.  he longest recorded one-day travel is 265 miles!

The first spring monarchs usually arrive in KS the second week in June, and we can expect the main weave of fall migrants through KS in mid-September. Those west of the Continental Divide migrate to and overwinter along the south and central California coasts, and a few of the eastern individuals migrate to and overwinter in Florida.  Some stay there, becoming non-migratory. But most monarchs attempt the 2-3,000 mile journey to central Mexico. A few stop, breed, and lay eggs in Texas, producing a fifth generation that migrates south. 

The fourth (and fifth) generations are different: they halt sexual development during fall migration but complete it before their first spring breeding in the USA.  Monarch larvae (caterpillars) feed on milkweed leaves and juice. TX is striving to provide ample milkweed for the large spring larval "hatch" that occurs there.