This Week's Update Includes:

• News: Recovering Monarch Tags
• Scientific Discovery: Cold Triggers Spring Migration
• The Migration: Maps and Journal

"We had an adventure and made some exciting discoveries," Estela reports this week.

Over 200 Recoveries
Almost all of the 200+ tags recovered at El Rosario were white Monarch Watch tags, meaning the butterflies had been tagged in the eastern U.S. and Canada. Monarchs from Michigan, Ontario, Texas, and Wisconsin were among those recovered. Tagging results like these suggest butterflies mix together at the same colonies regardless of where in the breeding range they originated.

• Look at the trees filled with monarchs and think about all of the different places they came from!

Two Blue Tags!
To the delight of Gail and Bob Morris of the Southwest Monarch Study, two blue tags were recovered. Blue tags mean the monarchs were tagged in the southwestern United States. Compared to the eastern region, far less is known about migration from the southwest so everybody was thrilled by the discovery.

Spectacular Clusters
The monarchs were more concentrated this week, and happened to form spectacuar clusters in the center of the area open to tourists.

"With this photo, there will be no doubt for my classmates and teachers that I was really here, seeing the monarchs live," said one little girl.

Thirsty Butterflies, Dry Conditions
Moisture becomes critical at this point of the overwintering season. The colonies break up as the monarchs move downslope in search of water. This year's shortage of moisture is concerning:

"Drought in the region is alarming right now. Puddles where monarchs drink water at the Sanctuary are a 'thin thread' of running water, compared to former years," notes Estela.

"The temperature at the overwintering sites is a critical component for the completion of the migration cycle. Without this thermal stimulus, the annual migration cycle would be broken," says Dr. Steven Reppert co-author of the study.

• Article: Cold Triggers Spring Migration

Cold Triggers Migration