Sombrero Marsh 🌱

by Dr. Oakleigh Thorne, II

Photo courtesy of Thorne Ecological


Sombrero Marsh is a very special place. It’s called a wetland. Our Thorne Ecological Institute office is located on this property. This was the result of a partnership that we put together in the late 1990s between the Boulder Valley School District (BVSD), the City of Boulder Open Space and Mountain Parks Department (OSMP), and Thorne.


About 50 years ago the east end of Sombrero Marsh began to be used regularly as a dump! All kinds of debris, such as old bricks, desks, books, cement, cars, fencing, roofing, and scrap metal, were dumped there. But in the mid-1970s Eric Miller, a science teacher from Centennial Middle School, was eating his picnic lunch by the marsh and saw a truck drive in and dump stuff there. He complained to the school board and administration that Sombrero Marsh was a valuable wetland. He was eventually able to get the dumping stopped. Only about one-third of the marsh had been filled. The rest was still in its natural state. I’m glad he acted when he did!


For many years BVSD owned the marsh and OSMP kept trying to buy it as permanent open space. But BVSD wanted to have environmental education involved in any sale of this property. That’s when Thorne Ecological Institute came into the picture. We offered to provide the environmental education programs. Everyone agreed that this would be a good solution. So this 40-acre marsh was sold to the city in 1999, except for one acre that the school district kept attached to their property. On this they built the Sombrero Marsh Environmental Education Center building from 2000 to 2001 with the funds they received from the sale of the land, plus some Great Outdoors Colorado (GOCO) funds and a generous grant from the Brett Family Foundation. The city then hauled away hundreds of loads from the old dump and restored a large section of the original marshland for educational purposes.


Thorne moved into the center in August 2001. We earn our rent by providing environmental education to mostly 4th Grade BVSD classes that come here on field trips for the full school day. They arrive about 9:30 in the morning, bring sack lunches, and stay until about 1:30 in the afternoon. We divide them into four groups, and they study birds, water insects, seeds, and water pollution. We rotate the groups every 45 minutes so each student gets to enjoy all four activities. At the end of the day they have learned a lot about what is a wetland, what lives there, and why it’s called a wetland.


Thorne Ecological Institute also has a Federal Bird Banding Station at Sombrero Marsh, so I often catch a bird to show the students. One of their favorite birds to see is a red-winged blackbird. They like to pat it on the head, but sometimes the bird bites them! They think that’s really “cool” to be bitten by a real wild bird. They never forget that, and it makes a good story to tell their friends and families. By the way, I teach a course in Birds and Bird Banding each June for 12-to 15-year-olds in our Thorne Natural Science School summer day camps. Each year we band hundreds of cliff swallows!


Sombrero Marsh is called a playa because it was scooped out of the salty Pierre Shale between 20,000 to 30,000 years ago by the wind. So it is indeed a salt marsh. There’s no stream flowing in or out of it. It’s a sort of bowl or low spot that collects rain and snowmelt that drains into it and fills it with water. When the weather gets dry for a long time, what we call a drought, it dries up completely. When it is full, it’s still only about a foot to 18 inches deep.


In the fall and spring, if there happens to be water in the marsh, many waterfowl, such as ducks, geese, phalaropes, and coots, use it as a resting spot during their migration. Just recently I have seen more than 100 ducks using it to feed and rest. We also see hawks, vultures, gulls, cormorants, and occasionally eagles flying over the area. We’re so lucky to have saved Sombrero Marsh as open space forever!


Dr. Thorne is founder and honorary president of Thorne Ecological Institute in Boulder. They have helped “connect kids to nature” for more than 55 years. For more information about Thorne Natural Science School classes for children, check www.thornenature.org or e-mail info@thornenature.org or call (303) 499-3647.

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