Mountain chiffchaff Caucasus, but interbreeding occurs rarely, if ever. The mountain chiffchaff differs from "tristis" in vocalisations, external morphology and mtDNA sequences. Its two subspecies appear to be distinct vocally, and also show some difference in mtDNA sequences. Mountain chiffchaff The mountain chiffchaff or eastern chiffchaff ("Phylloscopus sindianus") is a species of leaf warbler found in the Caucasus ("P. s. lorenzii") and Himalayas ("P. s. sindianus"), and is an altitudinal migrant, moving to lower levels in winter. The nominate subspecies is similar to the Siberian chiffchaff, but with a finer darker bill, browner upperparts and buff flanks; its song is almost identical
Common chiffchaff of London. These overwintering common chiffchaffs include some visitors of the eastern subspecies "abietinus" and "tristis", so they are certainly not all birds which have bred locally, although some undoubtedly are. The male common chiffchaff is highly territorial during the breeding season, with a core territory typically 20 metres (66 ft) across, which is fiercely defended against other males. Other small birds may also be attacked. The male is inquisitive and fearless, attacking even dangerous predators like the stoat if they approach the nest, as well as egg-thieves like the Eurasian jay. His song, given from a favoured prominent vantage