2026 Phenology Calendar Celebrates Family Legacy

The Aldo Leopold Foundation's fan-favorite Wisconsin phenology calendar is back earlier than ever for its 2026 edition! What is phenology? you may be asking. Only the most Leopoldian way to engage with the wildlife all around you. In his book, A Sand County Almanac, Aldo notes the arrival of geese in March, the blooming of silphium in June. Do you, too, notice the arrival of a favorite migratory bird, or the bloom of a particular wildflower? Phenology is the study of the timing of these seasonal events―and observing these changes throughout the year can grant you a deeper understanding and appreciation of what's happening in your biotic community.

“Keeping records enhances the pleasure of the search, and the chance of finding order and meaning in these events.” –Aldo Leopold

In 1935, Aldo Leopold and his family began recording detailed phenological observations while at the Shack. Everyone took part, but the youngest Leopold children―Nina, Carl, and Estella―were especially eager observers, competing with each other to see who would spot a first bloom or hear a first birdsong. The tradition of Shack phenology was nearly lost after Aldo's passing in 1948, with the family scattered across the country and their visits to the beloved Shack much more sporadic.

However, in 1976, Aldo's eldest daughter, Nina, moved back to Baraboo with her husband Charles Bradley, and the couple built their retirement home just a mile down the road from the Shack. In addition to hosting graduate students in the earliest iteration of the fellowship program and conducting research projects across the landscape that's now part of the Leopold-Pines Conservation Area, Nina started taking phenology notes again.

Later, in comparing over 20 years of her own records against those of her father's, Nina showed that many events were occurring earlier in the year than they had in Aldo's time. These findings were published in a groundbreaking 1999 research paper―co-authored by her brother Carl and Buddy Huffaker (then an intern, now our current Executive Director), among others―one of the earliest that used phenological records to demonstrate the ecological consequences of climate change.  

Learn more about Nina's paper, and other seminal research on phenology, at our phenology calendar resources page.‍

Our 2026 Phenology Calendar focuses on Nina's phenological legacy, honoring the 50th anniversary of her return to the Shack landscape, the impact her data and research has made on the field, and the ways the Leopold family bonded through nature observation. Monthly sidebars, curated by Dr. Stan Temple―Professor Emeritus at the University of Wisconsin - Madison, inductee to the Wisconsin Conservation Hall of Fame, and personal friend of Nina―reveal how the timing of blooms, migrations, and emergences shifted over the 35 years of her records, from 1976 until her passing in 2011. Additionally, selected quotes and photos offer an intimate view into Nina's perspective on phenology and ethical care for the land.

“My father would be so pleased to see the renewed interest in phenology today.” –Nina Leopold Bradley  

As the Leopolds proved, phenology is truly an exciting, educational activity for the whole family. Our calendar is a great tool to get you started, letting you know what to keep your eyes and ears peeled for each day. Enjoy gorgeous photos of Wisconsin flora and fauna throughout the year, with plenty of space to write in your own nature observations, appointments, and special occasions.  

This popular item continues to be one of the most sought-after items in the Marshland Market, helping readers discover “the pleasure of the search” and delight in all things natural, wild, and free. Treat the nature lovers in your life or start a family tradition of your own―get your calendars today! Order online, or stop by the Aldo Leopold Foundation now through October 31st to pick up the 2026 Phenology Calendar in-store.

Calendars available while supplies last, with special rates for bulk order purchases. Buy yours today!

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Thank you to McFarlanes' Retail and Service Center for sponsoring the 2026 Phenology Calendar.