Molecular tools reveal diets of insectivorous birds from predator fecal matter

Abstract

The emerging field of molecular scatology enables critical testing of food web theory. The non-invasive application of molecular tools allows for sequencing of prey DNA from predator fecal matter, evaluating diet breadth and foraging guild. While insectivorous bats are obscure foragers compared to most insectivorous birds, more is known about which arthropod species bats consume because molecular techniques have been optimized for mammalian systems, not avian physiology. Our research objective was to use molecular tools to detect arthropod prey in the fecal matter of an insectivorous avian predator. We used Western Bluebird (Sialia mexicana) as a model predator due to its generalist foraging strategy. We compared two fecal DNA extraction kits: (1) Qiagen's DNA stool mini kits, used widely in dietary studies on bats and (2) Zymo's Soil/Fecal DNA MiniPrep kits, not currently cited in the molecular scatology literature. We successfully extracted DNA only with the Zymo kit, amplified mitochondrial cytochrome oxidase c subunit I genes, sequenced, and identified the arthropod prey. A spiked PCR experiment showed evidence of possible inhibitors remaining in the Qiagen kit extractions. Overall, arthropod prey from seven different orders and five different classes were identified. We discuss the ecological implications of these data and suggest areas of future research applying molecular techniques to avian fecal matter.Consistent methodological advancement will enable molecular scatology to identify ecosystem services provided by insectivorous birds, develop ecological theory, and inform predator conservation efforts.

A molecular analysis to assess codling moth Cydia pomonella L. (Lepidoptera: Tortricidae) predation by orchard birds

“…Mols and Visser, 2002), are limited in their ability to definitively identify avian species providing the pest removal service. In light of these challenges, molecular scatology is a powerful, non-invasive indicator of biological pest control (Jedlicka et al, 2013). A variety of DNA-based methods are available for analyzing bird droppings, with advantages and disadvantages that must be considered in the context of the research questions.…”

“…Birds in our study may have excreted the remains of their prey prior to sample collection. However, while mist netting in the mornings may have missed opportunities to detect birds consuming adult C. pomonella during periods of evening activity (Jedlicka et al, 2013), other life stages of C. pomonella were available to birds at all times of day. For instance, eggs are laid directly on apples and leaves, larvae are found on apple leaves and on the surface or the interior of the fruit, and pupae are typically in the tree bark or soil before reemerging as adults (Solomon et al, 1976).…”

“…Field samples were extracted in the same manner using only the optimal extraction kit (see Results). Extractions were purified using OneStep TM PCR Inhibitor Removal Kits (Zymo Research, Irvine CA) prior to PCR to reduce PCR inhibition caused by uric acid present in avian feces (Jedlicka et al, 2013). Adult C. pomonella DNA was extracted from one specimen using a DNeasy® Blood and Tissue Kit (Qiagen) by crushing two dry C. (Simpson et al, 2013).…”

“…Furthermore, tools for studying biological pest control have advanced dramatically as well. In situ observation of C. pomonella in bird diet is labor intensive and often impractical while morphological identification of invertebrates in stomach contents or fecal samples produces coarse and incomplete taxonomical results due to the challenges in identifying easily digestible or larval prey (Jedlicka et al, 2013;Symondson, 2002). Molecular (DNA) detection of prey items from feces can be a less invasive, nondestructive alternative that has the potential to be a more accurate indicator of species interactions (Symondson, 2002).…”

“…While DNA-based methods for analyzing bird droppings are not novel (e.g. Jedlicka et al, 2013;Karp et al, 2014), they have not previously been applied to investigate bird predation of C. pomonella.…”