Here Come the Monarchs!
Monarch Butterfly Field Notes from Mexico by Dr. Bill Calvert

Listen to Dr. Calvert 

March 12, 2008
Yesterday we arrived late mainly because of the myriad of new "topes" (speed bumps) in the roads, a sure sign of burgeoning population and development in rural Mexico. It was cool and cloudy at Chincua, the kind of clouds that let some radiation through. The butterflies were high above us, some flying, some basking, most in high, scattered clusters all 100 feet or more above our heads. We were disappointed.

But even in our disappointment we could see forces that effect butterflies at work. The cloud cover would thin and thicken. As it thickened, and less radiation reached the basking butterflies, they pushed off from their positions and took to the air. This important behavior ensured that they would not be trapped in exposed positions by rapidly falling temperatures on the surfaces of the trees. When the clouds thinned, the butterflies in flight would find new basking positions or return to protected positions in their hanging clusters. The effect on us was a pulsing — or a thickening and thinning —of flying butterflies in the sky.

Today was totally different. We arrived early above the tiny community of La Salud in an arroyo at the edge of the forest in a field. Butterflies had already begun to stream down the arroyo, coming from the main Rosario colony up above, or from clusters formed when butterflies had left Rosario days before.

 Orange, flying, flapping, gliding creatures filled the forest clearing, until we felt we could scarcely breathe.

Rosario was breaking up, and we were witnessing its breakup in the arroyo below it. As the cloudless day warmed, more and more butterflies joined the downward stream, some flying above the canopy, some filtering through the forest. The tempo increased with some stopping to drink and others channeling themselves along roads and pathways. Orange, flying, flapping, gliding creatures filled the forest clearing, until we felt we could scarcely breathe. It was astonishing, and marvelous, and a welcome return for me after two years' absence.

It was clear when we passed through Angangueo that, from the butterflies pointed northward —flying northward— that they're on their way home. Or let's say on their way to their breeding area. It was incredible.