Common chiffchaff and generally pale legs. Bonelli's warbler ("P. bonelli)" might be confused with the common chiffchaff subspecies "tristis", but it has a plain face and green in the wings. The common chiffchaff also has rounded wings in flight, and a diagnostic tail movement consisting of a dip, then sidewards wag, that distinguishes it from other "Phylloscopus" warblers and gives rise to the name "tailwagger" in India. Perhaps the greatest challenge is distinguishing non-singing birds of the nominate subspecies from Iberian chiffchaff in the field. In Great Britain and the Netherlands, all accepted records of vagrant Iberian chiffchaffs relate to singing males.
Genomic evolution of birds bird bones. Something similar occurs with the respiratory system. In mammals, the total inner volume of lungs changes during ventilation. However, this does not happen in birds. They make the air circulate through their lungs by contracting and expanding their air sacs. Five genes are involved in this process in mammals and birds. Feathers are one of the most characteristic features of birds, alongside with the beak. Feathers are formed of α- and β-keratins. Compared to reptiles and mammals, α-keratin protein family has been reduced in birds, whereas β-keratins has expanded enormously. Since every major bird lineage possess at least