Journey North on learner.org provides weekly updates that described bustling activity in the first half of March as the Monarchs flew in crowded masses on the forested slopes, then mated prior to beginning migration. Though last summer's ideal conditions allowed the population to rebound somewhat from the previous year's record low, numbers overwintering were still only a fifth of what is considered average--the whole eastern migratory population covering a mere three acres. This map shows how the monarchs are concentrated in El Rosario, the main tourist location, with the rest scattered at various other locations nearby.
With the passenger pigeon the stuff of legend, it's remarkable to live in a time when a species still masses in such numbers that a March 5 update can still say
"The monarchs would come out of the trees each time that cumulus clouds covered the sun. They reached almost unbelievably dense numbers, flying out over the llanos. The trees were nearly emptied at such times. Literally every cubic foot of air held at least one monarch."A report of "Massive mating..." comes on March 12. But the next week's report is less sanguine. By March 16, the leading edge of the migration typically crosses over the Rio Grande into Texas, but this year the departure has been delayed. A March 19 update reported that cold weather is delaying departure, and "Terrible weather at the sancturies" was reported on March 16, as heavy rains and strong winds plagued the sanctuary for two days straight.
Five decades ago, we didn't even know where the Monarchs overwinter. Only when things start to go wrong does one have to start figuring out how something works, whether it's a car engine, one's body, or a wondrous annual migration. What once was dispensed free of charge by a generous nature now might not survive without human intervention.
Working in local habitats, I've seen what nature can do when a restored balance unleashes the native growth energy. The Monarchs are one more example of the tremendous capacity of nature to thrive, if only we give it a chance.