Catching flycatchers: High congruence of field and molecular identifications of Empidonax (Passeriformes: tyrannidae) flycatchers highlights the feasibility of accurate in-hand identification

Abstract

Recent avian population declines highlight the importance of long-term bird monitoring data such as those collected from bird banding stations. Empidonax flycatchers are considered some of the most difficult bird species to identify in North America because of their phenotypic similarity. To determine the congruence of in-hand field and molecular identifications, we collected blood and feather samples from Empidonax flycatchers captured during bird banding in southeastern Utah from 2013 to 2017 and generated cytochrome c oxidase subunit I DNA barcodes for these individuals. While we expected to see numerous incongruencies due to these species' phenotypic similarity, we found that field and molecular identifications matched for 92.7% of individuals examined. This suggests that Empidonax flycatchers can often be accurately identified in the field when banders use carefully collected morphological data in their assessments (including tail length, wing minus tail length, bill size and shape, and calculations based on specific feather measurements). Our findings highlight the importance of using detailed morphometric data while banding Empidonax flycatchers, indicating that these kinds of additional measurements can lead to a high degree of accuracy with Empidonax in-hand identifications. However, we also show the merit of molecular identifications to supplement field identifications in cases of unknown individuals, rare species, or closely related species with overlapping geographic ranges.

Long-term monitoring data when bird banding require accurate species identification. Empidonax flycatchers are considered one of the most difficult bird lineages to identify in North America. We studied how often field and molecular identifications are congruent for North American Empidonax flycatchers. We collected blood and/or feather samples from flycatchers in southeastern Utah between 2013 and 2017 and generated short DNA barcodes (similar to 400 base pairs) for 103 samples. We found that field and molecular identifications matched for 92.7% of the flycatchers included in our study. Our findings emphasize that Empidonax flycatchers can be accurately identified in the field when banders collect detailed trait information to support the identification process.