DUTCH BIRDINGVOLUME 42 • NO 4 • 2020 Identification of Oriental Cuckoo and Common Cuckoo based on primary pattern Petteri Lehikoinen & Roni Väisänen dentification of Oriental Cuckoo Cuculus opta- tour feathers between the two but the information Itus has always been a topic of lively discussions is slightly contradicting. Payne (2005) describes among birders in Europe. As an extremely rare va- juvenile Himalayan as having broader white fring- grant to Europe (outside Russia), the species has es on crown, back, and wing­coverts and tips of gained an almost mythical reputation. The cur- inner secondaries than Oriental, whereas Erritzøe rently known plumage differences between Orien­ et al (2012) report these being buffish in juvenile tal and Common Cuckoo C canorus overlap con- Himalayan and white in juvenile Oriental. A he- siderably and are difficult to assess in the field patic morph occurs in both Oriental and Hima­ (Cramp 1985). The lack of reliable identification layan (Erritzøe et al 2012). The songs of these two features for Oriental, besides vocalisation, is sur- species differ from each other, which is the most prising. This lack of knowledge might result in a important feature to identify the two (Lindholm & vagrant Oriental being overlooked in Europe, es- Lindén 2007, Xia et al 2016). pecially during migration periods when records The precise distribution ranges of Oriental are more probable. During migration, birds usu- Cuckoo and Himalayan Cuckoo in China are un- ally remain silent, unlike in the breeding season clear (Payne 2005, Xia et al 2016). Based on song when they are actively advertising territory through differences, Himalayan occurs north to Shanxi vocalizations. and north­east to Hebei and Oriental south to The aim of this paper is to shed some light on Liaoning (Xia et al 2016). According to Payne the plumage features of Oriental Cuckoo and on (2005) and Erritzøe et al (2012), birds in Taiwan separating it from the different subspecies of belong to Himalayan based on their small size. Common Cuckoo by studying museum specimes. However, Xia et al (2016) found that their song is Nowadays, a substantial proportion of birders are more like Oriental. equipped with cameras, and the features present- Common Cuckoo is more widespread than ed in this paper can be interpreted even from Oriental Cuckoo and most authors recognize four flight photographs of lower quality. subspecies: C c canorus (hereafter nominate ca- no rus), C c bangsi (hereafter bangsi), C c sub tele- Range and geographical variation phonus (hereafter subtelephonus) and C c bakeri Oriental Cuckoo has a more eastern breeding (hereafter bakeri) (eg, Payne 2005, Erritzøe et al range than Common Cuckoo. Oriental breeds in 2012, Gill et al 2020). Nominate canorus breeds Russia from west of the Ural mountains all the in Europe and across Russia, Kazakhstan, Mon­ way east to Kamchatka and winters south from golia and northern China, as far east as Kamchatka south­eastern Asia to Australia (figure 1). The re- (figure 1). The breeding range of bangsi is restrict- lated more southern species Himalayan Cuckoo ed to the Iberian peninsula and extreme north­ C saturatus was formerly considered conspecific western parts of the Maghreb. Bakeri breeds from with Oriental (Erritzøe et al 2012) but is nowadays north­eastern India, Bhutan and north ern Vietnam often treated as a full species (eg, Dickinson & to south­eastern China. Sub telephonus has a Remsen 2013, Gill et al 2020). Himalayan is breeding range from the southern Caspian Sea to widely distributed in south­eastern Asia and a southern Mongolia and the extreme north­west- shorter­distance migrant than Oriental, wintering ern parts of China. Bangsi and most nominate south to New Guinea. It is remarkably smaller in canorus winter in Africa, south of the Sahara. size than Oriental (Erritzøe et al 2012), although Subtelephonus winters in India and eastern parts there is some overlap (Payne 2005). Oriental and of Africa, whereas bakeri and eastern populations Himalayan are very similar in plumage. Literature of nominate canorus winter in south­eastern Asia presents differences in the fringes of juvenile con- (Cramp 1985, Erritzøe et al 2012). However, there [Dutch Birding 42: 229-247, 2020] 229 Identification of Oriental Cuckoo and Common Cuckoo based on primary pattern Allo C canorus Sym C canorus & C optatus Sym C canorus & C saturatus 107 15 11 27 canorus 15 specimens -2 3 bakeri/ 16 bangsi subtelephonus 4 subtelephonus - >10 13 11 C canorus bakeri C optatus C saturatus FIGURE 1 Map showing rough distributions of Common Cuckoo Cuculus canorus subspecies, Oriental Cuckoo C op- tatus and Himalayan Cuckoo C saturatus (Payne 2005, Erritzøe et al 2012, Xia et al 2016) together with collection localities of studied museum specimens. Pale red: allopatric occurrence of Common; pale violet: sympatric occur- rence of Common and Oriental; pale orange: sympatric occurrence of Common and Himalayan. Dashed area: uncertain situation of distributions of Oriental and Himalayan (see text). Literature is inconsistent regarding sub­ species of Common occurring in central China and maybe both C c bakeri and C c subtelephonus occur (see text). Collection localities shown in dots, where colours represent taxon collected (see legend). Size of dots represents number of samples collected on each site. Number of samples indicated in dots for localities with sample sizes >10. is recent evidence that birds breeding in north­ size as nominate canorus, although Cramp (1985) eastern Mongolia and Beijing, China, also migrate mentions that typical individuals in Central Asia to winter in eastern Africa (Beijing Cuckoo Project are as small as bangsi. The underwing­coverts and 2019). Literature is not consistent with the subspe- axillaries of subtelephonus are said to be less cific status of birds in central China, which might barred (Erritzøe et al 2012). In contrast, bakeri is be due to phenotypic variation (Payne 2005). darker on the upperparts than nominate canorus According to Cramp (1985), the distribution of and has denser barring on the underparts. Similar subtelephonus continues east through Mongolia to bangsi, bakeri is not known to have a hepatic and northern and central China as far as Japan, morph (Erritzøe et al 2012). In size, bakeri is de- and due to their intermediate size, the eastern scribed as slightly smaller than nominate canorus birds could be separated as their own subspecies, and subtelephonus (Payne 2005). C c telephonus. However, currently telephonus is not usually considered a valid subspecies (eg, Gill Vagrancy of Oriental Cuckoo in Europe et al 2020, Payne et al 2020). Despite the potential for vagrancy of Oriental The variation in phenotype of these apparently Cuckoo into Europe as a Wetsren Palearctic (WP) clinal subspecies has not been extensively de- breeder and long­distance migrant, a recent scribed (eg, Cramp 1985, Erritzøe et al 2012). record in Finland is the only one outside Russia Bangsi differs from the other subspecies by its we are aware of. Furthermore, in the (greater) WP small size. The hepatic morph is unknown in and outside breeding range, Oriental has oc- bangsi (Erritzøe et al 2012) but some females are curred as a vagrant only in Israel (a juvenile ringed said to have extensive rufous on the breast (Cramp and photographed at Eilat on 17 August 1985; 1985). Subtelephonus has whiter underparts and Shirihai 1999) and Iran (two records in 1898: on thinner black bars on the breast than nominate 20 April (collected) and 28 September; Khale­ canorus. It is also paler on the upperparts than ghizadeh et al 2017). The observations (n=35) in nominate canorus. Subtelephonus is similar in New Zealand, c 2000 km from the nearest winter- 230 Identification of Oriental Cuckoo and Common Cuckoo based on primary pattern ing grounds in eastern Australia (Miskelly et al Material and methods 2017) represent the vagrancy potential of the spe- The previous identification problems in this spe- cies. Therefore, the small number of observations cies meant that the Sotkamo bird got special at- in the (greater) WP outside breeding range is tention by the Finnish rarities committee. In June somewhat surprising. 2015, long recordings of song and calls were ob- The Finnish record concerned a territorial male tained and it was captured for close examination. at Sotkamo in the eastern part of the country. The Thanks to widely available reference material, it bird was found singing in the summer of 2015 and was concluded that the vocalisations of the returned to the same location in 2016 (Väisänen Sotkamo bird corresponded with typical Oriental et al 2016, 2017; cf Dutch Birding 37: 272, plate Cuckoo. However, reference material for meas- 422­423, 2015; plate 304, 308). Following this urements and plumage details were scarce. There­ record, there were some suggestions that Oriental fore, in 2016­18, we studied the collections of the Cuckoo may have been overlooked in Finland Natural History Museum, Tring, England; the and that it could be a more frequent visitor. Fin­ Zoological Institute of the Russian Academy of land has a breeding bird monitoring scheme con­ Sciences, St Petersburg, Russia; and the Finnish sisting of a grid of transect lines in every 25 km, Museum of Natural History, Helsinki, Finland. and, in addition, a different scheme concentrating Altogether, we investigated 314 specimens of the on protected areas. If the species occurred annu- four subspecies of Common Cuckoo, 153 of ally in Finland with several singing individuals, Oriental and 19 of Himalayan Cuckoo (table 1, we would presume it to be encountered in either figure 1). Only specimens collected roughly in the of these monitoring schemes, or accidentally by breeding season (mainly May­August) were con- birders more often than once. It is noteworthy that sidered, although this does not safely exclude in- there are three earlier reports of singing birds from dividuals on migration.