Different phylogenetic characteristics of Icterids: would they be evolutionary strategies to avoid parasitism by Molothrus spp.?

Some birds exhibit the behavior of nest parasitism, which involves laying their eggs in the nests of other species to be incubated and cared for by the adoptive parents. Among all the studies conducted on this subject, there is a gap regarding the nest type of nest parasites and their hosts. Therefore, using species from the Icteridae family, this study aimed to identify if there is a tendency for more closed nests to be less parasitized than open nests and if there is a phylogenetic relationship between them. In this context, we expected open nests to be an ancestral condition to closed nests, serving as an evolutionary feature to avoid nest parasitism. We also analyzed other characteristics such as the number of eggs, nest type and parental care. As a result, we observed that open nests were more common, while closed nests were predominant in a specific clade and some isolated species. The analyses indicated a phylogenetic signal clustered within the Icteridae family concerning nest types, which may imply a selective pressure. However, we cannot assert that it is a direct response to nest parasitism, as closed nests are also parasitized, specifically by M. oryzivorus. Parental care and diet type also showed phylogenetic signal, indicating that these changes were not random. However, we did not observe associations in host selection by the parasites based on these characteristics. Furthermore, we found a progression in the number of species parasitized by Molothrus spp. along the phylogenetic lineage. We also observed a similarity in host choice between M. ater and M. aeneus, indicating evolutionary convergence, as they are not sister groups.