Have Asian koels evolved egg mimicry with any of their hosts?

The Asian koel Eudynamys scolopaceus is a generalist brood parasite that exploits a diverse array of host species across Asia. A previous study using avian visual modeling found no evidence that koels had evolved eggs that mimic the eggs of one of their oldest known hosts, the house crow Corvus splendens, or that they had host‐specific egg types when parasitizing two other common hosts in Bangladesh. In this study, we used museum collections to compare eggs from three koel subspecies to a broader range of host species from multiple areas across Asia. Our goals were to: 1) determine if koel eggs differed in appearance based on the host species they parasitized, and 2) determine if koel eggs appear similar to the eggs of any of the hosts we measured, which might suggest egg mimicry. We found no evidence that koels have evolved host‐specific egg types (all koel eggs were similar in appearance to each other regardless of the host nest) or that koels had evolved egg mimicry with house crows. Rather, koel eggs were the most similar in color to the red‐billed blue magpie Urocissa erythrorynhca in all geographic regions and were more similar in pattern to the other parasitized crow hosts than to house crows in the same geographic region. Thus, there is some evidence that koels may have evolved eggs that mimic the eggs of these other hosts, rather than the eggs of the house crow, but further experimentation to test these hosts for egg rejection ability is warranted.