The moths that make up birds’ meals: DNA “bar-codes” used to identify prey of the Whip-poor-will.
Usually, scientists use traditional taxonomy—a system based on physical characteristics, such as the number of wing spots or legs—to identify species. Increasingly, however, scientists are looking within the cells of plants and animals to identify them, with the help of molecular geneticists interested in biodiversity. Together they are bringing new insights to taxonomy, genetics, ecology and park stewardship.
Over the last several years, scientists have taken mitochondrial DNA (mtDNA) samples from about 1,000 (out of 1,600 known) species of moths in the park. This mtDNA is inherited from moth’s mothers, and functions within the cell to turn food into energy the moth can use. With mtDNA we cannot tell individuals apart but it is useful for identifying which creatures are related; we couldn’t tell Bob and Sally apart using their mtDNA, for example, but we could tell that they are human and maybe even related. Researchers working with the moths can rapidly “read” a segment of the mtDNA and compare that record with a library of these samples. By doing this, they can identify the moth species from just a small amount of otherwise unidentifiable tissue such as eggs, larvae or even digested stomach contents from birds.
In this case, the bird whose meal is in question is the Whip-poor-will (Caprimulgus vociferus). These are medium sized nocturnal birds that feed on insects while flying. Little is known about certain aspects of their life history, including what their prey species are. We would like to know, because they are thought to be declining in some regions of the eastern United States.
When a whip-poor-will was killed by a vehicle in the Park in 2008, the stomach contents were removed and sent to the University of Guelph’s Biodiversity Institute of Ontario. Researcher Elizabeth Clare was able to extract mtDNA sequences of four different species of moths from the “soupy” gut contents of the birds. Upon analysis, she found that one of the moths in that meal was rather uncommon.
This is thought to be the first instance of moth species being identified from bird gut contents, and it opens up the potential for new ecological investigations. Researchers with the All Taxa Biodiversity Inventory (ATBI), a project to identify all species in the park, have also sequenced the mtDNA of many aquatic insects in the Smokies, and the cataloguing of some groups such as birds is completed nationally.
Read more about the All Taxa Biodiversity Inventory.