In the wee hours of the morning, our blurry-eyed team packed our van and drove (safely) to various sites throughout The Ridges in Door County. Once the necessities were unpacked (comfy chairs and snacks) we set up our mist nets. When I watched the first bird being processed, with every feather being meticulously looked at, I could not help but be in awe of the incredible knowledge base these bird banders had. Bird banding is a very useful technique in monitoring migratory patterns of birds, however it does not provide a complete picture when applied to birds who are small and travel long distances in short time frames.

Bird banders hard at work at the UW-Milwaukee field station

A new method currently being researched involves tracking migratory songbirds using stable isotopes, and frankly, I find it fascinating. Now before I continue, I understand that some of you may ask: "Wait, what is an isotope?", or, "Yeah, I have some chemistry background, but how does that relate to the birds I see outside my window every day?" Well, while I consider myself a novice scientist, this topic is new to me and I will try my best to explain:

Ever hear the term "you are what you eat"? Well, this is true for birds too (I would know given that I cleaned cedar waxwing berry-stained poop before). Basically scientists can monitor isotope levels of carbon (C), nitrogen (N), and hydrogen (H) in bird feathers and compare them to isotope trends found in water and flora (food) throughout the US. Isotopes are simply forms of elements that are different due to the amount of neurons in their atom, thus changing their atomic mass. Changes in hydrogen isotope levels can be attributed to variation in cycles of evaporation and precipitation due to elevation. Similarly, carbon levels can vary due to latitudinal growing conditions which alter photosynthetic pathways (C3 versus C4 plants).

Now that we can predict these isotope levels, how do we compare those to birds? Well, most migratory birds undergo an annual molt between July and September and the isotopic levels found in their food during that time are reflected in their feather composition. These isotopes are then processed via isotope ratio mass spectrometry and compared to known isotopic compositions. While you cannot trace exact locations, scientists can now get a better understanding of bird migration patterns which will allow us to create better management plans for species of concern. Pretty innovative? I think so!

Written by: Vanessa Komada, UEC Community Science Intern

Learn more about research at the Urban Ecology Center and how you can get involved here.

References:

• Geological Society Of America. "Isotopes From Feathers Reveal Bird Migration." ScienceDaily. ScienceDaily, 6 November 2003. .
• Kelly, Jeffrey F, and Deborah M Finch. “Tracking Migrant Songbirds with Stable Isotopes.” TREE Vol. 13, No. 2 February 1998.
• “Stable Isotopes.” Edited by Peter Marra, The Migratory Connectivity Project, www.migratoryconnectivityproject.org/stable-isotopes/.