International Crane Foundation

Exploring Changes in the Eastern Sandhill Crane Population over 50 years

Data visualization: Dorn Moore, Jim Cunningham, & Randy Garcia
Research Team: Anne Lacy, Jeb Barzen, Dorn Moore, Kristin Norris

In 2015, researchers at the International Crane Foundation published a paper in the “Journal of Field Ornithology” titled “Changes in the number and distribution of Greater Sandhill Cranes in the Eastern Population” (download the original article). The research team used data from annual bird surveys to explore the substantial changes in the population between 1965 and 2013. To help explore the data used in our analysis, we worked with a team of graduate students at the University of Wisconsin to build interactive tools to help you explore the data.

For winter analysis, the project team used data from the National Audubon Society’s Christmas Bird Count. Volunteers - citizen scientists - count birds as part of the Christmas Bird Count between December 14 and January 5 each year. These data are used by researchers to help understand changes in bird populations. Our analysis of these data revealed both major increases in the number of Sandhill Cranes in the eastern population, but also significant changes in the timing and distribution of cranes during their winter migration.

Population Trend for Sandhill Cranes in the Eastern Population (1966-2013)

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A trend in the changing population of Sandhill Cranes is reflected in the number of cranes counted each year in the Christmas Bird Count. - Data from National Audubon Society Christmas Bird Count.

The majority of Sandhill cranes within the eastern population spend their summer/breeding months in or north of Michigan, Wisconsin and Minnesota. The data visualization below helps explore both the changes in numbers of cranes from 1965 to 2013 but also the changes in the distribution of the cranes during the Christmas Bird Count. It is easy to see the northward shift in the distribution of Sandhill Cranes and also how they spread to areas along the gulf coast and the eastern seaboard.

Use the slider above to change the year.

Sandhill Cranes Counted at each Christmas Bird Count Location

Although these data do not necessarily reflect the ultimate wintering area for Sandhill Cranes in the region, they do reflect changes in the areas that will still support cranes as winter arrives. Sandhill Cranes are hardy birds; many of them will wait to migrate until open water for roosting and drinking has frozen over completely. Sandhill Cranes are able to postpone their migration until later than the Christmas Bird Count each year. The research team documented a significant northern shift in the average latitude of the eastern population at the Christmas Bird Count each year. The chart below shows the northward shift and the broadening range of latitudes where Sandhill Cranes are staging or wintering each year.

Average Latitude of Sandhill Cranes Recorded in Christmas Bird Count (1966 - 2013)

The changes in the average latitude for Sandhill Cranes in late December and early January reflect changes in the population, changing habitat and food sources, and a change in the climate during the same period. The northern trend of the average latitude (orange line) over time is accompanied by an envelope (blue area) showing the core of the population's spread across different latitudes.