Evaluating the use of environmental DNA for surveying semi-aquatic avian fauna

Abstract

The identification and quantification of DNA shed into aqueous environments can be used to estimate site occupancy and population density of various taxa. It is often easier to sample for environmental DNA (eDNA) than use traditional surveying techniques, and results of eDNA analyses are often more accurate. The sensitivity and efficiency of eDNA sampling makes it a useful tool for conservation biology. Detection of eDNA is particularly useful for aquatic species that are rare or difficult to survey, though it may have promising applications for less aquatic species as well. I tested the hypothesis that eDNA can be used to detect the presence of Canada geese, a semi-aquatic bird species. I screened pond samples from central Oklahoma for the Canada goose NADH dehydrogenase subunit 2 (ND2) mitochondrial gene using a species-specific primer-probe with quantitative, real-time PCR (qPCR). Canada goose eDNA was detected at all ponds sampled, including those where Canada geese were absent during sampling. eDNA detection rate increased as goose abundance increased and was unaffected by other environmental variables (e.g. temperature, pH, water flow). These results may be due to increased eDNA production where Canada geese are more abundant. The pond environments were relatively homogenous and did not significantly affect eDNA presence and detection. Overall, eDNA can be used to detect Canada goose DNA in ponds and potentially to monitor other bird species which are rare, endangered, cryptic, or difficult to survey (e.g. black rail, Laterallus jamaicensis). Used in conjunction with conventional surveying techniques, eDNA can aid in the conservation of rare and threatened species across a wide range of taxa, including semi-aquatic birds.