The Nature Writers of Texas

The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Sunday, September 24, 2006

It Is Again Time for Monarchs
by Ro Wauer

The fall monarch migration through our part of Texas is due any day now. The major portion of the southbound monarchs that pass through our area can be expected by mid- to late September and to continue through most of October. The majority of the migrants will move out of our region into Mexico by the end of October. And this year should be another big year, in spite of previous concerns about impacts to their wintering grounds in Mexico.

Good news about monarchs comes from an article by Mike Quinn, TPWD Invertebrate Biologist, in "The Texas Nature Tracker," a TPWD newsletter. Mike wrote that surveys of wintering monarch colonies by Mexican biologists in the Monarch Butterfly Biosphere Preserve in Michoacan in 2005 revealed numbers "nearly tripled in size, from a record low of 2.19 hectares the previous winter to 5.92 hectares of occupied forest habitat last winter!" He added that "The annual benchmark is represented by the size of the forest area occupied rather than the actual number of insects due to the widely disparate estimates of between 10 and 50 million monarchs per hectare."

The monarch preserve lies at about 10,000 feet elevation, where periodic freezes occur. Last winter was relatively mild and the wintering monarchs were not subject to deadly freezes as they had during the previous winter. That combined with loss of habitat had resulted in some serious declines in the number of over wintering monarchs.

But by mid-March 2006, Texans were seeing above average numbers of northbound migrants, including groups, rather than single monarchs. These spring migrants were "on the final leg of a sojourn" that had "begun half a continent and over a half year ago." Mike pointed out that these migrants, "composed of worn individuals approaching the eighth month of their adult life, and coincides with the insect’s lowest annual population level." The spring migrating females that found milkweeds (larval foodplants) layed eggs and continued northward, although the majority of these old-timers soon perished. It was their offspring and their offspring that continued northward into the Great Plains, the Midwest, and further north into Canada.

Mike reported that "by the end of June 2006, the monarchs were still expanding to new locations in Canada with many observers reporting above average numbers of all stages of monarchs!!! All individuals in terms of monarch observations and current weather conditions in the upper Midwest suggest that this might be a banner year for the mighty monarch butterfly!"

Observers interesting in sending their monarch observations can do so either to Texas Monarch Watch, 3000 S. IH-35, Ste. 100, Austin, TX 78704, or directly to Mike Quinn at


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