Abstract
Four Common Chiffchaffs Phylloscopus collybita trapped in the United Arab Emirates (UAE) during winter and early spring were identified as Phylloscopus collybita menzbieri (three birds, two trapped December 2020 and one March 2019) and P. c. abietinus (one bird, March 2019) on the basis of genetic analysis of mitochondrial genes ND2 and cytb. These three records of menzbieri represent the first confirmed records of P. c. menzbieri away from the taxon’s breeding range in uplands of the southern Caspian region, Iran c. 1,300 km from the UAE. The appearance and vocalisations of these birds and the implications of this finding for the subspecies of Common Chiffchaff wintering in the UAE are discussed.IntroductionThe Common Chiffchaff Phylloscopus collybita is a polytypic species, with six subspecies currently recognised across its range (Gill et al. 2021): three ‘northern’ subspecies (nominate collybita , breeding in western and central Europe; abietinus, breeding in northern and eastern Europe; and tristis, breeding in Siberia) and three ‘southern’ subspecies (brevirostris, breeding in northern Anatolia, Turkey; caucasicus, breeding in the Caucasus; and menzbieri, breeding in Northern Iran and Turkmenistan). Morphological differences between subspecies are subtle, which makes identification to subspecies level of birds away from the breeding grounds problematic. However, there are genetic differences between most subspecies. Helbig et al. (1996) and Rakovi? et al. (2019) identified six separate genetic clades, corresponding to collybita, abietinus, tristis, a joint caucasicus/brevirostris group, menzbieri, and an unnamed population breeding on Mount Hermon, Israel. Consequently, genetic analysis is now being used extensively to resolve subspecific identification of Chiffchaffs on migration or in winter (e.g. Collinson et al. 2018, van der Spek & de Knijff 2021).Chiffchaffs are widespread and often abundant winter visitors and passage migrants across much of the Arabian Peninsula, including the United Arab Emirates (UAE) (Pedersen & Aspinall 2010; Porter & Aspinall 2010). However, the morphology of the Chiffchaffs occurring in the UAE and Oman varies somewhat, and the subspecific identity of birds wintering there and migrating through have long been subject to uncertainty. There has been speculation as to whether more than one subspecies is occurring and, if so, the relative numbers of each and the timing of their occurrence (e.g. Eriksen & Victor 2013, Campbell & Smiles 2021). While collybita is less likely to occur (based on its westerly breeding range, and a mainly southwestern or southerly orientation towards its wintering grounds), any of the southern breeding subspecies (caucasicus, brevirostris and menzbieri) may be expected to occur (Dubois 2010), as may the northern/eastern European abietinus and the Siberian tristis. It was previously widely assumed that tristis regularly reached the Arabian Peninsula in winter (e.g. Porter & Aspinall 2010). However, recent advances in the understanding of field characters and non-breeding distribution of tristis (e.g. Dean & Svensson 2005, Dean 2009, de Knijff et al. 2012) has shown that tristis seldom occurs in the UAE and significant doubt must now be cast on earlier records that were previously regarded, despite lack of thorough documentation, as tristis. Based on song, at least three examples of tristis have been suspected since 2008 in the UAE, but lack of adequate documentation meant that none of the records were formally submitted for assessment. Several other recent claims, based partly on call, were deemed not proven by the Emirates Bird Records Committee, which was concerned about a general lack of observer awareness of the typical calls of southern-breeding subspecies, which can sound extremely similar to those of tristis. While it is plausible that tristis may indeed occur at least occasionally, it is certainly not considered to be a frequent visitor to the UAE; wintering Chiffchaffs in the UAE sing commonly in late winter and early spring and invariably have a song broadly typical of Western Palearctic-breeding taxa, and thus quite unlike that of tristis (see below).