Pooper Snoopers: Deciphering Diet Composition of Purple Martins from Insect DNA in Fecal Samples
Dr. Anna Forsman, University of Central Florida
Purple Martins consume thousands of insects daily. Although some of these prey items are large and conspicuous, such as dragonflies, others are much more difficult to identify visually, especially at a distance, through binoculars. Because of this, it has been difficult to make comprehensive assessments of Purple Martin diet composition. To address this research need, we have applied a molecular method known as DNA metabarcoding to identify diet composition from traces of insect DNA in fecal samples collected from Purple Martins. We collected fecal samples from Purple Martin nestlings in Erie (PA), Winnipeg (Manitoba, Canada), and from nestlings and adults in Orlando (FL). Insect DNA was extracted from fecal samples and used to sequence a small portion of the insect genome, which is variable in sequence among insect species. By comparing DNA sequences to a database of known insect species, we were able to identify the diet items consumed by Purple Martins across these three different breeding sites. We detected a total of 71 different prey species, representing 29 families and 10 orders of arthropods. Although Diptera (flies), Lepidoptera (butterflies/moths), and Odonata (dragonflies) were the most frequently consumed prey, we found quite a bit of variation in the frequency of other arthropod prey groups among the three sites that we sampled. In this seminar, we will take a deep dive into the dietary habits of Purple Martins and talk about how we plan to use DNA metabarcoding to learn more about their foraging ecology in the future.