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The hunt for orange September, searching for monarch roosts

Many Monarchs roosting in an oak tree

It was early on a hot September morning that I turned into Goose Lake Prairie. I had arrived too early for a program and thought I would spend a few minutes in the picnic area listening to those sweet early morning sounds of nature. And then there it was — an unfamiliar, subtle sound — a strange flutter, repeating...almost like a heartbeat. 

I expected to find an injured mourning dove trying to gain traction for liftoff, but no - nothing. I looked up into the trees — elm, maple, oak — only to see several browned-out patches of leaves. But then a fissure of sunlight cut through the trees. I struck gold — well, orange really — there were hundreds and hundreds of monarchs hanging from the branches fluttering about, readying for takeoff. 

I had stumbled on my first large monarch roost of the Eastern North American monarch butterfly (Danaus plexippus). I walked around transfixed like I was in nature's high cathedral. And I couldn't wait to share this news with my Master Naturalists. And once I did, things will never be the same for my Fab Four who became The Secret Society of Monarch Roost Hunters. 

Led by Phyllis Schulte, a long-time Master Naturalist and Will County Forest Preserve Steward, and equally as passionate and dedicated Master Naturalists Jo Chenell, Kathy Hearne and Sally Skoff have been on the hunt to find and learn more about the monarch roost sites in our area every year. All four of these volunteers are also Illinois Butterfly Monitors, with Phyllis having clocked in more than 25 years surveying our local butterfly populations. 

Spectacular Supergeneration

Monarchs have four generations, the first three live only a bit over a month. The fourth generation of monarchs is the one that lives for nine months and endures a 4,000 mile trip from as far north as southern Canada to their winter home in Mexico — not bad for a being our smallest migratory animal that weighs just about as much as a small paperclip.

Yet when they overwinter in Mexico en masse, their combined weight sometimes breaks branches of the oyamel fir trees they overwinter on. Beginning in late August, this super generation begins migrating south. This same group will alight from Mexico after winter, bound for Texas, where they mate, lay eggs, and end their personal journey. It will be their children and grandchildren that continue the path back to their summer homes in the north. 

The mystery of the monarch roost

But how do monarchs know where to go? And who sent out the invitation for the nightly roosts? How do they coalesce?

Scientists are still working on these answers. It was once thought that a pheromone was the 'invitation' but further research has not borne that out. It is clear that several factors play a part in roost behavior. Scientists theorize the roosts are an anti-predatory strategy that follows the old adage "safety in numbers." Roost behavior is considered an essential part of migratory survival. 

Our roost-hunting team did as deep a dive into the available research to gather clues to identify possible roost sites to scout. Being on this dedicated team has a 911 emergency style schedule. Kathy will head out early and look to the skies to see monarchs starting to stream. When she saw gathering, she calls the others and everyone jumps in their car to meet at the potential roost site. It's a crazy hide-and-go-seek nature game. 

"Kathy observed around 200 monarchs yesterday, by the time I got there, they were nowhere to be found. While I was hoping to see an early wave, yesterday was not the day. I guess this is like fishing. You just never know. I'm always going to show up if I get a call because that's when the big ones get away. Hopefully, next time."
— Sally Skoff

Monarchs migrate during the daytime. But at dusk, they gather together in trees — sometimes just a few dozen, other times in the thousands-to shelter and rest for another leg of their trip. Sometimes the roost is fleeting, only one night. Other times they may return to a roost site for a week or two. It was thought that monarchs followed the same migration highway every year, but as more data is gathered, it is not the route that is necessarily the same. It is what functional environmental aspects are available. 

Roost Clues

Dr. Bill Calvert, a monarch scientist from University of Massachusetts Amherst has studied this roost behavior and overwintering monarchs for years. He suggests the important factors related to monarchs choosing a roost site and, if we are lucky, ways we can perhaps find a roost. 

These practical factors, we as Master Naturalists and everyday community scientists can observe, are roosts occur very near a good nectar source, which isn't always easy to find in late summer/early fall. Fields of goldenrod and asters are ideal. Roosts are in trees that provide protection and shelter from the wind. Our volunteers found roost sites in deciduous trees, but roosts can also be found in a conifer's dense foliage as well. 

Dr. Calvert observes that monarchs roost downwind of the wind direction. Our winds typically, both winter and summer, come predominantly from the south and west. There are also geographic, topographical clues — roosts are found in depressions and ravines, further protecting them from the elements. Another roost site clue is if you spot a tree 'oasis' where there is a cluster of trees in an otherwise open area. 

If you want to follow monarch migration, and post your own observations, the website Journey North is the place to go. This science-based organization 'employs' volunteers to help collect thousands of data points to increase knowledge through real-time actual sightings — roosts, first spring sighting, and many other natural phenomena. And perhaps you can start your own nature search party for roost sites in the hunt for Orange September. 


Nancy Kuhajda is the Agriculture and Natural Resources Program Coordinator for the Master Naturalist, Master Gardener and Master Composter Programs in Will and Grundy Counties in Northeastern Illinois. Nancy has a bachelor's degree from the University of Illinois at Urbana Champaign and has Graduate Certificates in Crop Science and Horticulture. Nancy also writes a weekly column for a local Joliet paper on nature and gardening topics. Nancy's passion is to bring understanding of the natural world to the community at large but particularly to the underserved urban youth, special needs, and elderly in congregate housing in the community. 

Naturalist News is a blog by University of Illinois Extension Master Naturalist staff and volunteers who bring you stories highlighting the individuals, places, wildlife, and plants that make this state amazing. Join us each week to learn something new, be inspired, and become connected to your own community by recognizing the amazing ways we are all intertwined. Want to get notified when new Naturalist News posts are available? SIGN UP HERE!