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
Birds of the Danube Delta and especially of feeding the deltaic biotopes are providing in the warm season of the year. This phenomenon is also supported by the presence – in different deltaic biotopes as against the common ones – of some species, which in the rest of their area cover other life environments. The species of non-brooding deltaic birds were classified into the biotopes they visit while resting on the Danube Delta's territory and they are connected to by the way these biotopes are providing their food. The ornithological biotopes of the Danube Delta belong to three well-individualized habitats, namely the aquatic, the amphibian