Monarch Butterfly Field Notes from Mexico by Dr. Bill Calvert

Field Notes from Mexico by Dr. Bill Calvert

March 9, 2004

Photo: Jim Edson

Dr. Calvert Calling Journey North from Mexico

(Audio File mp3)

NASA Visible Earth

Chincua Revisited and Reassessed
This week we are a new group of teachers from New Jersey, Ontario, Canada, Connecticut, Pennsylvania and Delaware.

Keeping to our itinerary we visited the Piedra Herrada in mid-day. The butterflies were not streaming down the mountain in the numbers we had seen in previous weeks. Possible reasons were unseasonably cool temperatures accompanied by high winds, which kept most of the butterflies in their roosts. Also possible was the movement of the colony to a new location the north face on the mountain. If so, they would be expected to descend to water on that side instead of our side. The presence of many cars and a few busses in the parking lot suggested that tourists were still being taken up the mountain and that the butterfly colony was still intact.

As if to compensate for the lack of butterflies one of our group spotted a Mountain Trogon sitting with its back to us forested canyon below Herrada. This amazingly colored bird, related to the famous Quetzal of Central America, flew off displaying its brilliant red, white and blue-green plumage. The spotter received many extra points.

The following day we changed our itinerary slightly. Trekking up to the Chincua colony instead of Rosario, we had decided to Rosario because the colony had been so devastated by the storm. German, our driver, who is also the Symbolic Butterfly Migration mailman, protested claiming there would be no blue tortillas for lunch. Fortunately for us he was wrong. The tortillas were present and, as always, delicious.

We trekked the two miles over the Llana de Horunda 11,000 feet and then down, down into the canyon called Caoja (sp?). A new aggregation, consisting in parts of trees, had formed up high near the ridge line. We had seen such formations before in response to a nectar source. It is possible that this was the cause of this bud colony, as a nearby fire break was full of flowering Eupatorium. A high wind impinged upon the ridge from the southwest. But both the bud colony, and the main colony below, were well sheltered from these winds.

For the first time we were able to see the leading edge of the Chincua colony. Previously we had seen only its upper edge and had estimated that there was only ½ hectare covered with butterflies. The new view of the leading edge, and all in between, required a new assessment of its size. Butterflies in densities expected for this time of year covered at least 3 hectares, possibly as much as 4 hectares, of terrain. Our inability to find the evidence of the enormous piles of dead butterflies seen at Rosario may be explained by the absence of these. The Chincua colony protected by the dense forest Caoja Canyon and the high ridge facing the high altitude westerly winds, may have fared much better than we originally thought. We hope so, anyway. Chincua was really a pleasant surprise. I’ll tell you. It was huge!

Tomorrow we visit the Pelon Colony for the first time. They say that the Pelon colony is also gorgeous and, you know, intact and healthy. But I’ve not seen it yet. More about this in the next report.

Maps and images of monarchs at their winter refuge in Mexico.

NASA Visible Earth