Canvasback and parasitic redhead egg identity data

Validating the accuracy of protocols and field observations is important to maintain consistency amidst changing observers or study sites. To aid inferences on interspecific brood parasitism, we validated 200 field observations of egg identification to the species level against mitochondrial DNA sequencing for nests where interspecific brood parasitism was suspected. Of the samples submitted for sequencing, 29 failed to sequence resulting in 171 DNA verified samples of canvasback (Aythya valisineria) and redhead (Aythya americana) eggshell membranes. We found observers were highly accurate at differentiating eggs between the two species despite experience level, and hatched eggshell membranes contained the best quality tissue samples for sequencing success when compared with eggshell tissue samples from earlier in incubation. Our investigation showcases the utility of non-invasive molecular techniques to validate field protocols and rejects egg identification as a major source of uncertainty when trying to account for interspecific brood parasitism in parasitized canvasback nests.