Siberian chiffchaff Siberian chiffchaff Siberian chiffchaff ("Phylloscopus (collybita) tristis") is a leaf-warbler which is usually considered a subspecies of the common chiffchaff, but may be a species in its own right. Siberian chiffchaff breeds in Siberia east of the Pechora River and winters in the lower Himalayas. It is also regularly recorded in western Europe in winter, and it is likely that the numbers involved have been underestimated due to uncertainties over identification criteria, lack of good data and recording policies (Sweden and Finland only accept trapped birds). Because of their unfamiliar appearance, British records in the 1950s and 1960s were originally
The Origin of Birds the reptile." He also finds the eyes of birds and reptiles to be remarkably similar, especially the development of the lens, as well as the ear, which reveals a much wider gap between the Sauropsida and mammals than with birds. He describes the sexual organs of birds and reptiles to likewise be structurally similar, and finds that while most species of male bird have lost the penis to reduce weight, those that retain it bear remarkable similarities to extant reptiles. He writes that secondary sexual characteristics are also similar between birds and reptiles, with both groups frequently utilizing bright colors