Why We Track
We often get asked why we track the eagles. The simple answer is to collect data about them. To date, we've learned D1's migratory paths and summer and winter ranges, observed an interesting difference in dispersal patterns between D1 and D14, discovered that D14 was electrocuted, and saved Four several times before she died from electrocution in March of 2015. We hope that the transmitters we've attached this year will tell us whether or not siblings have any connection after dispersal ("Do they travel together?") and reveal more about dispersal patterns in male eagles. While we lost track of D1 in 2014, her transmitter revealed a clear preference for three areas in northeast Iowa: Iverson’s Bottoms about ten miles northeast of Decorah, the Turkey River near Elkader, Iowa, and the Gilbertson Conservation area, also on the Turkey River, west and north of Elkader. These would be good places to look for her!
So what do we do with the data? Our eagles are part of a new research project spawned by observations from an earlier study on migration behavior dynamics of primarily adult Bald Eagles in the Upper Midwest (see Mandernack et. al.), the only study of its kind in this region. Two subadult eagles, a two y-o and a three y-o, were part of this study. Pre-satellite transmitter eagle migration research suggests immature eagles are highly nomadic. Mandernack et al. did not observe noticeable migration behavior differences between the two immature eagles and the adults, and felt more information was needed to clarify immature migration behavior. If there is a difference in immature vs. adult eagle migration, when does this change occur? Is it gradual over the first several years of the eagle’s life or is the change abrupt?
D-1 was tracked to answer the most commonly asked question RRP received until 2011: “Where do the Decorah eagles go after they fledge?” Her migration behavior provided added impetus to study young eagle migration behavior more closely. Mandernack plans to track other first-year eagles to reveal answers to questions that will permit us to more effectively manage and care for this species. After all, how can we be effective managers/stewards if we do not understand basic species natural history/behavior/life requirements? The paper from the first study, which examines data collected between 1999 and 2006, was published in the Journal of Raptor Research in 2012. An abstract can be found at http://dx.doi.org/10.3356/JRR-10-77.1. We also share data with the Iowa DNR and conservation organizations working on habitat protection and research projects of their own. As Iowa's Wildlife Action Plan states, "Wildlife and fisheries management will be based on science." Our scientific data will be used to help conserve crucial habitat in a region that is under tremendous development pressure.
The Eagles (all eagles hatched from the Decorah nest)
- D1: Female eagle tracked from 2011-2014. May still be alive. Last tracked in Polar Bear Park, Hudson's Bay, ONT.
- D14: Male eagle tracked in 2012. Electrocuted in NC Iowa.
- Four: Female eagle tracked from 2014-2015. Electrocuted in EC Iowa.
- D24: Male eagle. Began tracking in 2016.
- D25: Male eagle. Began tracking in 2016.
The transmitter is made by North Star Science and Technology: http://www.northstarst.com. It is a small rectangular backpack that attaches to the eagles via teflon straps. It weighs about 55 grams, or roughly 2 ounces, and is solar-powered. Northstar's website lists the operational life as indefinite, but probably 2-4 years: our eagle biologist had one last as long as seven years.
For more information about the transmitter, please see this blog post.