The migration is moving southward slowly. Persistent south winds are holding the butterflies back. See what migration data predicts about the population.
Stop and Go
South winds have been holding the butterflies back. During most of October, a persistent weather pattern has remained in place. Cold fronts have been weak and have only twice dipped as far south as Texas. On only 4 of the last 19 days has the wind blown down from the north.
The pattern finally broke on October 12th. In the absence of headwinds butterflies moved across Texas in a clear pulse — including this remarkable report of an estimated 5,000 monarchs.
“A steady stream flying overhead for roughly 20 minutes, then a slow trickle for the next 40 minutes. I counted for 10 minutes and was counting anywhere from 230 to 282 every two minutes. There were monarchs anywhere from 2 to roughly 15 meters off the ground.” Christoval, TX October 13, 2016
“On the Woodridge Elementary playground on Friday afternoon, about 50 monarch butterflies were spotted flying approximately 10 feet above ground.” San Antonio, TX October 14, 2016
Tomorrow’s forecast shows a 2-day break from south winds. Without the wind impeding their travels, monarchs should flood into Texas on Thursday and Friday.
The migration has been underway for two months. What does the data we’ve collected so far predict about the population?
Look at the graph of overnight roosts. How do you think this winter’s population will compare to those in previous years?
Scientists will measure the population in Mexico in December 2016. This year’s results will be released by March 2017.