How do the butterflies find the roost?
Few people have had the chance to watch a roost form. One observer described it this way:

"The air resembled a Monarch airport, with monarchs coming in from every direction, floating through the air, checking out various trees, landing, then taking off again. It took from about 7:15 to 7:35 p.m. for them to cluster in the trees, just before dark."