Phenology is a branch of science focused on the relationships between climate and recurring natural events such as flowers blooming and birds migrating. Since 1936 the Aldo Leopold family has inventoried the phenological events that occur on and near their property (Sauk and Dane Counties, Wis.) Data collected over a 24-year period (1974-2000) by Nina Leopold Bradley, daughter of Aldo Leopold, was averaged to determine the phenological date on which events occur. These average dates were used in the calendar.

Also included in the calendar were five dates from Aldo Leopold's data (1936-1947) that occurred two weeks later than the most recent data. Several studies (Bradley et al. 1999, Leopold and Jones 1947, Parmesan and Yohe 2003) have shown a significant trend for an earlier occurrence of spring phenological events, suggesting that some species are changing their behaviors in response to a warming atmosphere.

In addition to phenological data, each month included a section on land management practices, examples being Nest Structures for Birds, Water Management, etc?

The calendar was distributed to more than 4,000 individuals throughout the state, including many landowners who have participated in the U.S. Fish and Wildlife Service's, Partners for Fish and Wildlife program or the Natural Resources Conservation Service's, Wetland Reserve Program.

Photos for the calendar were donated by Jack Bartholmai, volunteer photographer for the Horicon National Wildlife Refuge.