Long-tailed Tit (Aegithalos caudatus) - HBW 13, p. 95

Taxonomy: Parus caudatus Linnaeus,1758. Sweden.
Often treated as conspecific with A. glaucogularis, but plumage distinctive, and no reports of regular intergradation or hybridization with latter species in NE China (apparent “intergrades” recorded as migrants in coastal Hebei, but origin and status of these unknown). Marked geographical variation. Races fall into four groups: “nominate group” in N Europe and Asia, “europaeus group” (including also rosaceus, aremoricus, taiti, macedonicus, tauricus) in S & W Europe, “alpinus group” (including also irbii, italiae, siculus, tephronotus, major, passekii) in Mediterranean Europe and SW Asia, and “trivirgatus group” (incorporating kiusiuensis, magnus) in S Korea and Japan (“europaeus group” and “trivirgatus group” are morphologically similar and usually combined, but marked geographical separation strongly suggests different origins). Where groups meet there are extensive areas occupied by variable populations of apparent hybrids, these areas of hybridization considered to be zones of secondary intergradation (where populations have met relatively recently). Nominate race intergrades with europaeus in Denmark, E Germany, S Poland, S Ukraine and N Romania, and with magnus in Korea; aremoricus intergrades with taiti in WC France; taiti intergrades with irbii in C Spain and Portugal; and europeaus intergrades with aremoricus in W France, with taiti in SW France, with italiae on S slopes of Alps, and with macedonicus in S of former Yugoslavia and S Bulgaria. Birds of this species breeding in Iraq and Syria of uncertain racial identity, provisionally included in tephronotus. Other proposed races are sibiricus (C Siberia), kamtschaticus (Kamchatka, in E Russia) and japonicus (N Japan), all poorly differentiated and thus synonymized with nominate; and pallidolumbo (Shikoku, in S Japan) and tarihoae (Cheju I, off S Korea), both merged with trivirgatus. Seventeen subspecies recognized.