Siberian chiffchaff to be a full species due to its distinctive plumage and vocalisations, being similar to "P. s. sindianus" in these respects. Common chiffchaffs (of the nominate race) and Siberian chiffchaffs do not recognize each other's songs. Pending resolution of the status of the form "fulvescens", which is found where the ranges of common chiffchaff (of the race "abietinus") and Siberian chiffchaff connect and may or may not be a hybrid between these, "tristis" is maintained in "P. collybita" by most checklists. Siberian chiffchaff Siberian chiffchaff ("Phylloscopus (collybita) tristis") is a leaf-warbler which is usually considered a subspecies of the common
Genomic evolution of birds or two cone opsin genes. Birds also seem to have lost the functionality of their right ovary. There are two ovary development-related genes, MMP19 and AKR1C3, that have disappeared in birds. The fact that a high number of genes related to spermatogenesis are evolving fast (which does not happen in those related to ovogenensis) suggest that males undergo a stronger selective pressure. The abundance of genomic data available nowadays has enabled research to elucidate the early evolution and divergence of bird groups, and has produced a much more detailed phylogenetic tree. Genomic research has shown that in order to make