Bell Museum Bird Specimens Test Out Trackers

Green herons are handsome birds, with suave dark flight feathers and a long neck patterned in russet and white. From the side, they almost look like they are wearing a suit — but instead of filing taxes, they work hard hunting small fish, frogs, crustaceans, and anything else that can be speared by the side of the pond. Unfortunately, that important work is at risk. Green herons have been declining across their range, and getting them back to regular business hours is a priority for researchers at the University of Minnesota. 

Green herons in the Bell Museum’s Bird Collection.

To save a species, it first needs to be understood. As beautiful as green herons are, their movement patterns are poorly known. That is where Hannah Slesinski, Elena West, and Mike Wells come in. Hannah Slesinski is a Master’s student under the guidance of Elena West, an avian ecologist, and John Fieberg, a statistical ecologist — both are faculty members in the Department of Fisheries, Wildlife, and Conservation Biology. Mike Wells is a USFWS Migratory Bird Biologist. Together, they are tracking the movement of green herons across Minnesota — literally. 

I joined Slesinski, West, and Wells in the Bell Museum’s collections, where they were examining green heron specimens, collected decades earlier. Slesinski separated the body feathers of an adult heron and placed a small device on its back. 

“See? It doesn’t quite fit.”

The device was a GPS tracker (also called a tag); tiny, solar powered, and used to map the migration and movement of green herons.

“Tagging data is an important tool for conservation,” Wells explained. “It can identify migration routes and critical stopover habitats, areas of breeding and dispersal, as well as identify key habitat characteristics for birds, [all of which] informs the best actions for conservation.”

In 2025, the heron team navigated a field season of bird tracking that did not quite go to plan. Green herons’ sleek suits — those long, glossy body feathers — proved to be an obstacle for the solar panels on top of the tiny trackers. The feathers were blocking the sun from reaching the solar panels, causing the GPS to lose power prematurely.

A preserved green heron being tested for a GPS tag. 

Luckily, solutions were waiting for the researchers amongst the rows of preserved specimens in the Bell Museum’s bird collections. Without unduly stressing a live bird, the team could test the fit and efficacy of a variety of different trackers on birds that were already preserved for science. After many measurements, Slesinski approved a new tag, the Ornitela OrniTrack-6 4G; it’s bulkier and heavier than the old ones, but the large solar panel should stick out from the glossy feathers of a green heron, especially if the feathers are slightly clipped upon capture.

The new tracker trade-off is not taken lightly, as every additional gram of weight means a little more energy spent by the heron to stay aloft. Herons captured and released this coming year will sport a heavier tracker, but Wells, having tracked many bird species in his role with the USFWS, is confident that the extra weight will not impact their behavior. The new trackers are within a safe weight range determined by the US Geological Survey’s bird banding lab. Once those GPS points start showing up this summer, Slesinski will be able to plot their movement.

“Hannah [Slesinski] brought creativity to the tracker problem,” Elena West, one of Slesinski’s advisors, reported, “and the Bell collections gave us the tools to test solutions without putting live birds through unnecessary stress. We are feeling great about going into this next field season on solid footing.”

Understanding where herons move can inform the conservation of sites in their path. It is an important step to ensure that the beautiful birds preserved in the Bell Museum’s collections will still be found wading through Minnesota ponds in perpetuity.

 “This was my first time working in the bird collections and interacting with the Bell Museum as a researcher, and I found the experience to be very fascinating…” Slesinski wrote in an email. “I appreciated how friendly and helpful the staff was at teaching me how to use specimens properly in order to get the answers I needed.”

Slesinski’s work amongst the drawers of preserved birds echoes the broader mission of the Bell’s collections: that carefully studying a few creatures in detail can lead to huge positive impacts for their species. Green herons collected decades ago will continue to provide answers for researchers whose questions — and the technology they use to ask them — have not yet been dreamed of.

Hannah Slesinski, right, hands a green heron specimen to Mike Wells, left.