A Million Monarchs Fill the Sky
Contributed by Dr. Bill Calvert

October 17, 2004
Cumbres de Monterrey, Nuevo Leon, Mexico

OK it’s Sunday the 17th--last weekend--and we were camped in an area in the Cumbres of Monterrey called Cienegas de Gonzales. We got a little bit of a late start but we were looking for roosts around 9:30--the sun takes awhile to get up over the canyon walls. So we found a few roosts. Some of them were just brilliant. [The butterflies] were hanging from Spanish moss and they just filled the mosses with bright colors.

We walked around for a little while, still looking for roosts, not seeing too many migrants. Seeing some migrants but not too many. But by 11 o’clock--between 11 and 12 o’clock--they were passing overhead by the millions.

"Seeing a million butterflies passing over is kind of magical," said Calvert.
Photos courtesy of Jonathan Dueck. (Click to enlarge.)

Listen to Dr, Calvert 

Millions of butterflies were up there kettling. You would focus your binoculars on near ones, on those in a kettle, and you’d keep changing the focus toward infinity and more butterflies would appear, higher and higher in the sky. It was just absolutely phenomenal. They continued just pouring over until about 1 o’clock and then they began to thin noticeably. And then we left that area, the Cienegas de Gonzales.

I’ve been along the route of the migration maybe 15 times, and I’ve seen some pretty spectacular stuff, but I think this is the most butterflies I’ve ever seen in migration over a particular area. I mean, this compares in density to what you see in early Nov at the butterfly colonies when they’re just arriving. The densities were just stupendous, they were just absolutely astounding. Seeing a million butterflies passing over is kind of magical.