To fill gaps in our understanding of black-crowned night herons in other parts of their range, we teamed up with biologists from The Ohio State University and Ohio Division of Wildlife to combine tracking data from the stable breeding colony at the Smithsonian’s National Zoo with tracking data from breeding colonies in the Lake Erie Plains region of Ohio, where the species is listed as state-threatened. We used the tracking data to see where these birds spend the winter and to see if this could be a reason there are differences in the population trends between the areas.
In June 2021, we published a scientific article in the Journal of Ornithology outlining the findings. We found that all the birds from the Ohio colonies migrated in winter, while some birds from the Zoo migrated shorter distances, some longer distances and others didn’t even migrate. The birds that did migrate from the Zoo shared similar wintering areas as the birds from Ohio, including Florida, Cuba, Honduras and Nicaragua. Some birds stayed in one place throughout the entire winter, while others moved around to different areas.
Most birds that we tracked for more than one year, returned year after year to where they spent the summer, no matter where they spent the winter. This means that where the birds spend the winter may not be the reason the Ohio black-crowned night heron colonies are declining. However, birds from these two distant areas mainly used only three locations to overwinter. Therefore, these areas may be important for conservation of the eastern North American population of black-crowned night herons.
Currently, two birds tracked from the Zoo are still transmitting location data. Both birds have been spotted at the Zoo and, in true Washington, D.C., fashion, one has been spending time on the National Mall.
And thus, after more than 100 years, our work with the Zoo’s colony of black-crowned night herons is done — at least for now. The birds will still return to the Zoo as they have for more than a century, but we don’t have any plans to put trackers on them any time soon.
This project was done in collaboration with Chris Tonra and Kristie Stein from The Ohio State University; and Laura Kearns from the Ohio Division of Wildlife. This research is supported in part by the Conoco Phillips Global Signature Program, Edgar M. Cullman, Jr., and the Smithsonian Women's Committee.