Development and parentage analysis of SNP markers for Chestnut-vented Nuthatch (Sitta nagaensis) based on ddRAD-seq data

Extra-pair paternity (EPP) is commonly found in socially monogamous birds, especially in small passerine birds, and there are interspecific and intraspecific variations in the extent of EPP. The Chestnut-vented Nuthatch (Sitta nagaensis) is a socially monogamous passerine bird, and verifying whether this species has EPP relies on parentage testing—S. nagaensis is not known to have EPP. In this study, we developed SNP markers of this species that are informative for parentage analysis from double digest restriction site-associated DNA sequencing (ddRAD-seq) data. A panel consisting of 50 SNP markers, with a mean heterozygosity of 0.343, was used to resolve 95% of nestlings to fathers. The combined exclusion probabilities for the first parent and second parent were 0.991 and 0.9999, respectively. This panel of SNP markers is a powerful tool for parentage assignments in S. nagaensis. In addition, we found that three offspring (7.9%) from three nests (23.1%) were the result of extra-pair fertilization out of 38 offspring in 13 nests. Our study provided information on parentage analysis that has not been reported before in S. nagaensis. It also supplemented the understudied EPP behavior of birds in Asia, contributing to a general understanding of the EPP behaviors of birds.