Field identification and ageing of Siberian Stonechats in ... · variability within and between these races is discussed, and some gaps in our knowledge of Siberian birds are addressed

Introduction and scopeThe Common Stonechat Saxicola torquatus iswidely distributed throughout much ofEurope and Asia, where eight races areusually recognised. Many more races (up to17, depending upon the authority followed)occur in Africa but assessment of these isbeyond the scope of this paper. In westernSiberia, the species is represented by the raceS. t. maurus (hereafter referred to as maurus),which is frequently recorded as a vagrant inwestern Europe. In breeding plumage,maurus and the European race S. t. rubicola(hereafter referred to as rubicola) can bear astriking resemblance to one another and theidentification of a vagrant Siberian bird inspring and summer can be challenging.

This paper reviews existing criteria andintroduces updates to the current under-standing of plumage variability among Euro-pean and Siberian birds. Emphasis has been

placed on assessing the validity of thedefining characters associated with males ofthe races maurus and rubicola although,where relevant, the races S. t. stejnegeri, S. t.hibernans, S. t. armenicus and S. t. variegatusare also discussed briefly. The two remainingPalearctic races, S. t. przewalskii and S. t.indicus, are restricted to the south and east ofthe region; they are less relevant from a Euro-pean perspective and not mentioned further.

A predecessor to this paper was publishedin 2005 in Vår Fågelvärld (Hellström &Wærn 2005), based on field studiesthroughout the Mediterranean region (fromthe Iberian Peninsula and Morocco east toTurkey, Cyprus and Israel) and Siberia. Visitsto Iran (2005), the Altai Mountains in Russiaand Mongolia (2007), and the Irkutsk Oblastand the Republic of Buryatia in south-centralSiberia (2004, 2005, 2008, 2009 and 2010)have enabled us to refine the earlier paper. In

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Field identification and ageing of SiberianStonechats in spring and summerMagnus Hellström and Mats WærnAbstract The Common Stonechat Saxicola torquatus is a widespread breedingspecies in the Palearctic region. This paper discusses the reliability of charactersthat enable birds from Europe (S. t. rubicola) to be separated from those breedingin western Siberia and central Asia (S. t. maurus), particularly during the breedingseason when differences become subtle. The current understanding of plumagevariability within and between these races is discussed, and some gaps in ourknowledge of Siberian birds are addressed. Emphasis is placed upon assessing thevalidity of the different characters. The timing and extent of moult and wear arecrucial to the understanding of these characters and of how they can affectappearance over time. Other Palearctic races are discussed where relevant.Careful observation and attention to detail are essential when faced with apotential maurus in Europe in spring but individuals of both sexes should providesufficient clues for identification, if seen well.

addition, we have examined specimens heldin the reference collections of the Museum ofNatural History, Stockholm (NRM), and theZoological Museum, Copenhagen (ZMUC),plus a large number of photographs from thebreeding grounds and migration stopoversites. Birds observed/photographed withintheir respective ranges during the breedingseason have been given extra attention.

Distribution and taxonomy The race rubicola breeds in northwest Africa,western, central and southern Europe east tonorthern Iran and Ukraine (see also Walker2001 for a brief discussion on the possibilitythat rubicola occurs regularly in southeastEngland). In westernmost Europe hibernansis found on the west coast of the IberianPeninsula, Brittany (France), Britain, Irelandand also, according to Munkejord (1981),locally in southwestern Norway. This last areaaside, Stonechats are absent from most ofFennoscandia, the Baltic States and westernRussia south to the northern shore of theCaspian Sea. To the east of this regionmaurus occurs from the eastern parts ofEuropean Russia, east to the Lake Baikalregion and south to Altai and northernAfghanistan. Farther east, stejnegeri replacesmaurus in eastern Siberia (Russia), Mongoliaand northern China to the Sea of Okhotskand Japan (Vaurie 1959; Dement’ev &Gladkov 1968; Cramp 1988; Urquhart 2002).In many respects little is known aboutarmenicus but the published breeding rangeincludes eastern Turkey, Armenia, thesouthern Caucasus range and the moun-tainous parts of northern and northeasternIran. Also in the Caspian region, variegatus isfound in the steppes to the west and north-west of the Caspian Sea, south to the easternCaucasus, where it also occurs at higher altitudes. See fig. 1 for the breeding range ofeach race.

Common Stonechat taxonomy is contro-versial and a range of views has been pub-lished in the last decade (e.g. Urquhart 2002,del Hoyo et al. 2005, Zink et al. 2009). Zink etal. (2009) presented evidence for treating thepopulations in the Palearctic as three species,based on geographical variation in mtDNAsequences: S. rubicola (including hibernans), S. maurus and S. stejnegeri. This treatment

may well prove to be the most rational onebut, for the time being, informed studiesfrom the reported zone of intergradation inSiberia are lacking, as well as from similarlyinteresting areas in eastern Turkey, Armeniaand northern Iran. Furthermore, the samestudy found haplotypes (sets of closely linkedgenetic markers on one chromosome whichtend to be inherited together) from thecentral Siberian clade (maurus) in a samplefrom Rostov-na-Donu area, just east of theSea of Azov, in southwest Russia, and haplo-types from the east Siberian clade (stejnegeri)in a sample from Astrakhan, west of theCaspian Sea. Both findings are rather unex-pected and controversial, and it may provepremature to draw any firm conclusionsabout the phylogenetic relationships ofmaurus and stejnegeri. Further input fromareas of potential hybridisation/intergrada-tion is required, and an analysis of nuclearDNA may be rewarding. In addition to Zinket al. (2009), genetic relationships betweenpopulations were discussed by Wittmann etal. (1995), Wink et al. (2002) and Illera et al.(2008), but unfortunately none of thesestudies included samples from either variegatus or armenicus.

For the purposes of this paper (andwithout taking a stand on the issue), we haveadopted the traditional approach toStonechat taxonomy and treat all taxa asraces of S. torquatus, in accordance with thecurrent treatment adopted by the AERC Taxonomic Advisory Committee (Crochet &Joynt 2010) and BOU (BOU 2010).

Intergradation and mixed pairingsOwing to the distribution gap in westernRussia, rubicola does not usually come intocontact with maurus during the breedingseason. We are aware of just one claim of amixed pairing of rubicola and maurus : a female rubicola and male maurus thatnested on Helgoland (Germany) in 1997(Gottschling et al. 2000). However, we havestudied photographs of the (presumedmaurus) male and, although superficiallypromising, we contend that the images lacksufficient detail to confirm the bird’s racialidentity. Furthermore, maurus is also isolatedfrom the Caspian races variegatus andarmenicus and, although their ranges

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Field identification and ageing of Siberian Stonechats

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approach to within a few hundred kilometresof one another in the southwest part ofcentral Asia, there is no evidence to suggestthey form mixed pairs. The situation inSiberia is more complex, with a wide range ofintergradation between maurus and stejnegerireported from the region between the YeniseyRiver and Lake Baikal (Vaurie 1959; Dement’ev & Gladkov 1968; Cramp 1988).These two subspecies are phenotypically verysimilar and we consider it inadvisable toassign field observations of single individualsoutside their breeding range to either race.Throughout this paper, discussion ofSiberian birds is based on maurus but inmost cases the criteria are also accurate forstejnegeri.

In easternmost Turkey, Armenia andnorthern Iran, rubicola and armenicus show asympatric breeding distribution. Urquhart(2002) stated that the two races show dif-ferent habitat preferences in that region, witharmenicus in montane habitats and rubicolain the lowlands. This is, however, a broad andsomewhat inaccurate generalisation sincerubicola also occurs in mountainous areas(for example, in 2005 we observed a breedingfemale rubicola at 2,200 m in the ElburzMountains, southwest of the Caspian Sea).Urquhart (2002) suggested that there is noevidence of hybridisation between rubicolaand either of the Caspian forms, although itis suspected to occur. Nonetheless, anyhybridisation is probably not widespread,and confined to a rather restricted zonewhere the ranges are sympatric. Regardingrubicola and hibernans, Cramp (1988) notedthat they intergrade in northwest France,western Belgium and the Netherlands.Plumage differences between these two racesare clouded by individual variation, however,and become apparent only when largersamples are examined. Owing to its generallydarker plumage, hibernans is less likely to bemistaken for maurus, and all charactersuseful when separating rubicola from maurusare also valid when separating hibernansfrom maurus.

Moult, ageing and sexingAn appreciation of moult sequence andtiming is essential for understanding differ-ences in the plumage development of rubi-cola and maurus. The timing and extent ofmoult in rubicola is well documented but formaurus the data are more limited and uncer-tain.

Moult in rubicolaA partial post-juvenile moult starts soon afterfledging and is usually finished in September,when the body plumage, lesser and mediancoverts and a varying number of tertials,alula feathers and greater coverts arereplaced. The primary coverts, primaries, sec-ondaries and tail are generally not moulted.Adults (2CY+) undertake a complete post-breeding moult in late summer, before theautumn migration, and this is usually com-pleted in September or early October. Nobirds, regardless of age, moult during thewinter months and breeding plumage isacquired by abrasion of feather fringes (Ginn& Melville 1995; Flinks 1999; pers. obs.).

Moult in maurusThe post-juvenile moult is similar to that ofrubicola but a) is usually completed a fewweeks earlier (Helm & Gwinner 2001); andb) is on average more restricted in extent,with fewer wing-coverts being replaced thanin rubicola (Svensson 1992; pers. obs.). Apartfrom the body plumage, many maurusreplace only the lesser coverts (Lewington etal. 1991; pers. obs.) and, consequently, manyyoung birds lack a moult contrast in thegreater coverts during autumn. Like rubicola,adults have a complete post-breeding moult,although this begins earlier and is usuallycompleted between mid August and earlySeptember (Helm & Gwinner 2001).

It is uncertain whether maurus has apartial pre-breeding moult (Svensson 1992;Urquhart 2002) but, in our opinion, there isenough circumstantial evidence to suggestthat most, if not all, first-winters undergosuch a moult. For example, Urquhart (2002)



Fig. 1. Breeding range of Common Stonechat Saxicola torquatus within the Palearctic region(modified from Urquhart 2002), showing the distribution of the races discussed. Outside thebreeding season the non-breeding ranges of the various races can overlap, particularly in the Middle East and the northern Indian subcontinent.

described captive maurus that attainedbreeding plumage by a partial pre-breedingmoult. Furthermore, many 2CY birds that westudied in spring and summer in Siberia haveshown a mixture of obviously fresh feathers(from a pre-breeding moult) and wornfeathers (from a post-juvenile moult) in thescapulars, mantle and nape, and sometimesalso on the head (plate 107). In some individ-uals this moult is more advanced, and suchbirds show a degree of fresh plumage thatspring rubicola seldom matches, and one thatis often apparent in the field. Moreover, likeSvensson (1992), we have examined speci-mens of first-winter male maurus that couldonly attain breeding plumage by moult.These specimens were collected in Octoberfrom Afghanistan and Sweden (plates 103 &104). The sex of both birds was establishedduring preservation, and is supported by thereplaced black axillaries or underwing-coverts, yet both showed a completely ‘femaletype’ plumage with medium-grey bases tothroat feathers. Intriguingly, some (perhapsmost) first-winter males do have black basesto the throat feathers, and the reason for thisvariation is a subject for further study.

Despite some anomalies, we suggest that apartial pre-breeding moult is the regularstrategy used by first-winter maurus. Theextent of this moult is evidently subject tovariation and has yet to be studied in detail,but appears to include a varying proportionof body feathers and lesser coverts, and occa-sionally some median and greater coverts andtertials. We do not yet know for certainwhether adult birds perform a similar pre-breeding moult, but there are some indica-tions to suggest that they do (for example,the freshness of the flank and belly feathers insummer, observed in most maurus, includingadults; see ‘Pattern of breast and flanks’below).

Ageing Stonechats in the fieldIn young birds, the post-juvenile moultcreates a moult contrast in the wing-coverts,which is present until the first complete post-breeding moult (when birds are about oneyear old). In rubicola a moult contrast isusually found among the greater coverts, ter-tials and/or alula feathers (e.g. plates 105 &118); it is usually conspicuous but the keyfeather tracts may at times be cloaked by

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103. (left) First-winter (1CY) male S. t. maurus, Bamian, Afghanistan, October 1949 (specimen heldat ZMUC, Copenhagen). Black axillaries establish the sex as male. Note that the chin feathers lackany trace of black (the feather bases are medium grey, but are not quite visible in this photo). A pre-breeding moult would be required for this individual to attain the black head of breeding plumage.

104. (right) First-winter (1CY) male S. t. maurus/stejnegeri, Landsort, Sweden, October 2008(specimen held at NRM, Stockholm). Sex established as male by blackish axillaries and underwing-coverts, and also by examination of the reproductive organs during preservation. Note the medium-grey bases to the lifted throat feathers. As is the case with the male in plate 103, a partial pre-breeding moult would be necessary for this individual to attain breeding plumage.

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overlying scapulars. Ginn & Melville (1995)stated that seven juvenile greater coverts areretained on average (by European birds); inour sample, the vast majority retained fewerthan five juvenile greater coverts. This dis-

crepancy may be due to different proportionsof rubicola and hibernans in the samples(rubicola might be expected to show a moreextensive moult due to its more southerlydistribution). In rubicola, more advanced



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106. Adult (3CY+) male S. t. rubicola, Belgium, June 2006. After breeding, adults have a completemoult during which all feathers are replaced. Compared with the 2CY male in plate 105, the entirewing is blackish-brown, less worn, and lacks the moult contrast present on that bird. During latespring and summer, a brownish hue is often present to the worn adult wing (especially theprimaries), making ageing less straightforward.

Marc van den Bril

105. First-summer (2CY) male S. t. rubicola, Tuscany, Italy, May 2009. Age is established by moultcontrast in the closed wing; the lesser, median and most of the inner greater coverts have beenreplaced during the post-juvenile moult, and these contrast with the rather worn and brownishalula, primary coverts, remiges and tertials, which are all juvenile. On this individual (and the male inplate 106) note the fine dark shaft-streaks on the rear flank just above the legs. This feature is morecommonly seen in rubicola than maurus.

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young birds that havereplaced all the greatercoverts are encounteredfrequently and thesecan still be aged by theretained juvenileprimary coverts andremiges. Adults do notshow a moult contrast(plate 106).

In first-wintermaurus the moult con-trast is often harder tofind than in rubicola, asfewer (if any) juvenilegreater coverts aremoulted. Even the mostadvanced birds seem to retain 4–5 juvenilegreater coverts, whilemost individuals aremore retarded andoften show contrastonly in the median orlesser coverts, which isharder to see in thefield. In spring, after thepartial pre-breedingmoult, the contrast isoften easy to find(plates 107 & 109), butuntil the moult patternof adult birds has beenestablished, we suggestthat it is inadvisable touse the presence of amoult contrast as anage-related character – an assessment of theextent of wear in theunmoulted feathers isnecessary.

Juvenile feathers areless resistant to wearand bleaching than sub-sequent generations.The degree of abrasiondepends on manyfactors, including diet,climate and habitat. Forexample, individualsmigrating through theMiddle East in spring

108. Adult (3CY+) male S. t. maurus, Astana, Kazakhstan, June 2003.Adults show a fresher and generally darker wing than 2CY males. Note the uniformly black wing-coverts, including the primary coverts.A brownish hue in the primaries is commonly seen in adult birds,especially in summer. Compare the cleaner flank colour of the males in plates 107 & 108 with the rather sullied and washed-out appearanceto the flanks of the rubicola males in plates 105, 106 and 120.

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107. First-summer (2CY) male S. t. maurus/stejnegeri, eastern SayanMountains, Russia, June 2010. Readily aged as 2CY by the almostcompletely retained juvenile wing (which appears brownish and worn as only the lesser coverts have been replaced). Some first-winterfeathers are still visible in the mantle and upper scapulars. Thesefeathers appear worn and rather uniform brown, and contrast with the adjacent fresh pre-breeding feathers that show a black centre andbroad, pale brown fringes.

will have spent the winter in a sunny, dry and generally demanding climate and thefaded first-year plumage is often readilyapparent, whereas birds that have wintered innorthwest Europe, where conditions are dulland damp, usually present greater difficulties.Note that the wings of adult birds, particu-larly the exposed primary coverts and pri-maries, will also appear rather brownish frommid spring onwards (plates 106 & 108).

The use of body contour feathers to age abird should be done with care, but duringspring many 2CY maurus show mantle andscapular feathers that were obviously grownduring the post-juvenile moult. Such feathersare very worn, often abraded to an apicalshape with diffuse and faded buffish edges,and with a rather pale, brown centre. Thisoften gives these birds a paler, brown-backedappearance, but it should be noted that freshfeathers from the pre-breeding moult maycreate a similar impression, especially withdistant views. Such feathers have fresh andbroad brownish edges and show a rather dis-tinct black centre. Consequently, irrespectiveof which feather generation is present, 2CYmaurus often shows a browner andpaler back than adults (plates 107 & 109).

Regardless of subspecies, it is oftendifficult to find moult contrast amongthe inner greater coverts since these arepredominantly white (which makesabrasion harder to assess). Not all indi-viduals, particularly maurus, can besafely aged in the field and some arebetter left unaged. Generally speaking, itis more difficult to establish the age offemales, and not possible for most inthe field.

Sexing Stonechats in the fieldSexual dimorphism in Stonechats isusually pronounced in breedingplumage, and determining the sex of anindividual is seldom difficult. Malesdisplay a contrasting plumage withblack crown, throat and ear-coverts, anda distinct white neck patch. Females aregenerally less contrasting and show apaler head and mantle, as well as lessdeveloped neck patches. However, somerubicola females are extraordinarilycontrasting and dark-headed, and in a



109. First-summer (2CY) male S. t. maurus,Altai, Russia, June 2007. This less advanced 2CYbird retains many heavily abraded first-wintermantle and scapular feathers (compare withthe more advanced 2CY male in plate 107).These feathers often wear to an apical shapeand show a brown centre. Note that thelesser and median coverts, some inner greatercoverts and perhaps also the inner tertial aredarker and non-juvenile (although, generally, it is not always easy to establish when featherswere replaced).

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110. Probable female S. t. rubicola, the Netherlands, July2006. Some rubicola females are extraordinarily dark,especially in summer, an effect that becomes morepronounced due to wear, and may result in a rathermale-like appearance. This individual is difficult to sex,and without additional details (such as age, rumppattern, etc.) birds such as this may at times be betterleft unsexed.

Erwin van Saane

few instances we have chosen not to assign abird to a particular sex (e.g. plate 110).Unlike rubicola and hibernans, male maurus,stejnegeri, variegatus and armenicus exhibitjet-black axillaries and underwing-coverts(plate 111); however, females of all racesshow pale greyish underwing feathers withpale buff edges (plates 122 & 123).

Racial identification of malesSeparation of breeding-plumaged male rubi-cola and maurus in the field relies on evalu-ating the colour of the underwing, rump anduppertail-coverts, while important sup-portive characters include the flank andbreast pattern, and the extent of the whiteneck patches. Other features, including theextent of white on the inner wing/shoulder,colour of the mantle, presence or absence ofwhite at the bases of the outer rectrices, thelength of primary projection and wingformula have been proposed. These are allvery difficult to assess properly in the fieldand most also vary to the extent that we con-sider them less reliable; they are not dis-cussed further here (but for details seeRobertson 1977, Jännes 1990, Stoddart 1992and Urquhart 2002). Identification ranges

from fairly straightforward to very difficultbut, although some birds are undoubtedlytricky to identify, most problems occur as aresult of brief or poor views.

UnderwingIn spring, the underwing-coverts and axil-laries of adult male maurus are uniformly jet-black (with narrow and indistinct palefringes when still fresh), and contrast sharplywith the pale greyish underside of theremiges (nearly pure white on the basal halfof the remiges; plate 111). According toSvensson (1992), 2CY maurus may showsome variation, and some birds are said toshow a paler underwing.

In contrast to maurus, rubicola usually hasa paler underwing and shows less contrastbetween the underwing-coverts/axillaries andremiges (plate 112). This is partly due to thecoverts and axillaries being mid or dark greywith broader whitish tips and edges, andpartly a consequence of the remiges havingduller bases. However, not all birds are quiteso straightforward. For example, Corso(2001) discussed birds nesting in Sicily thatshowed a darker underwing than typicalrubicola; he described this as blackish and

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111. (left) Adult (3CY+) male S. t. maurus, Altai, Russia, June 2007. The axillaries and underwing-coverts in male maurus are generally jet-black and contrast sharply with the silvery-white bases to the secondaries and primaries. This pattern is not known to occur in rubicola.

112. (right) Adult (3CY+) male S. t. rubicola, Öland, Sweden, March 2009. In male rubicola, theunderwing is typically paler and less contrasting than in maurus. The pattern and colour of thismale’s underwing is typical of most European birds, but some can show darker underwings. As ageneral rule, in rubicola the primary underwing-coverts are the darkest feathers of the underwing,and most birds (like this one) show paler feathering closer to the body.

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only slightly paler than that of maurus. Wehave also studied several rubicola with dark-looking underwings and these have indeedshown blackish (or dark grey) underwingprimary coverts and dark greater, medianand lesser underwing-coverts. However, withgood views (or photographs) the proximalpart of the underwing-coverts and axillariesare often revealed to be paler, showing widerpale edges to the feathers, frequently contin-uing distally into the arm, and creating a palearea along the central part of the underwing.Importantly, although dark rubicola dooccur, we have not found any with an under-wing pattern matching that of maurus.

In conclusion, uniformly jet-black axil-laries and underwing-coverts are strong evi-dence of maurus. In blurred photos, or withbrief field views, however, dark rubicola maybe misidentified, but we emphasise that it isgenerally the nature of views/photos that arethe problem, rather than the true pattern ofthe bird (plate 113).



114. (left) First-winter (1CY) male S. t. rubicola, southern Israel, November 2008. This freshlymoulted male shows a fairly typical rump pattern with white feather bases, and rusty tips anddistinct blackish markings to the uppertail-coverts. Note the fresh tertials that were replaced in the post-juvenile moult (and which contrast with the paler and more worn juvenile secondaries and primaries). This contrast establishes this bird as a 1CY. Unlike Siberian birds, male rubicolaalready shows a well-developed blackish head and throat during first autumn.

115. (right) Adult (3CY+) male S. t. maurus, Altai, Russia, June 2007. Note the unmarked and purewhite rump and uppertail-coverts. On many males, including this bird, the white extends up thelower back and is visible above the folded wings. Adult male maurus shows a fresher and generallyless brown wing than 2CY males.

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113. Male S. t. rubicola, Scania, Sweden, June2008. The true pattern of the underwing canoften be hard to judge. In the field, as well asin blurred photographs, darker rubicola maygive the observer an erroneous impression ofblack underwing-coverts. The identity of thisindividual was established as rubicola fromother photographs that illustrated the patternof the rump, flank and underwing.

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Rump and uppertail-covertsMale rubicola in spring shows a darker basalcolour to the rump with the central partvarying from brownish to white, and withdiagnostic dark (blackish) markings near thetip of each individual feather (plate 114). Apure white rump patch is rather commonlyseen, but the white patch is smaller and moresquare-shaped than in maurus. Quite a fewrubicola also show virtually unmarked whiteuppertail-coverts, especially in more wornplumages; however, when scrutinised at closerange, even the most heavily worn birds willusually exhibit dark markings to one or twoof the longest uppertail-coverts. Under fieldconditions, these darker markings can bevery difficult to determine, owing to the factthat the feathers are resting on the under-lying dark rectrices, so that the dark tipsappear to vanish into the background (plate117). Ullman (1986) observed a breedingmale in Morocco in April which lacked darkmarkings to all the uppertail-coverts. Wehave also studied a few rubicola whichappeared to show entirely white uppertail-coverts, but the plumage of these birds washeavily abraded and the longer uppertail-coverts appeared to be broken or evenmissing. As a rule, the longest uppertail-

coverts are likely to retain dark markings atthe tips, and are usually the last feathers tolose this pattern. We have yet to find anyrubicola that lacks dark markings to all theuppertail-coverts in fresh plumage.

117. Male S. t. rubicola, Morocco, January 2009. This individual could, at first glance, be mistaken formaurus but note the dark markings at the tip of the worn, longer uppertail-coverts (which are hardto see against the black rectrices), and the rather restricted white rump patch, which does notextend up the back. Such birds are not uncommon within rubicola, and great care is required toestablish the precise pattern of the white rump and whether dark tips are present.

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116. Male S. t. maurus/stejnegeri, southwest of Irkutsk, Russia, June 2005. In maurus, thewhite rump patch frequently (but not always)extends onto the lower back. Note that thisbird still retains some peachy feather tips inthe lower rump area. Here, the breast patch isweakly defined and replaced by a rather palepeach hue, which is a feature sometimes seenin maurus.

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118. First-summer (2CY) male S. t. rubicola, Bulbjerg, Denmark, May 2008. An individual with amaurus-like appearance; the conspicuous white rump, large white shoulder patch, small and paleorange breast patch and rather generous white neck patches combine to create this impression.Closer examination of the tips of the longest uppertail-coverts reveals the diagnostic dark markingsshown by rubicola. The identification was further confirmed by other photos showing the underwingpattern and colour. Furthermore, the pure white part of the rump is rather restricted and does notextend onto the lower back. This bird can be reliably aged as 2CY by the contrast between theblackish lesser, median and greater coverts, alula and tertials and the brown retained juvenileprimary coverts, primaries and secondaries.

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In fresh plumage, maurus exhibits a peach-ochre rump and uppertail-coverts that lack dis-tinct dark markings. During spring, thepeach-ochre feather tips are worn away, revealinga pure white rump and uppertail-coverts.During the transition, irregular patches of palepeach-ochre and white may be visible (plate116). Rarely, some maurus may show finegreyish shaft-streaks to the uppertail-coverts(plate 126), but this should not be confused withthe distinctive blackish and bold markingsusually shown by rubicola. The size of the whiterump patch varies to some extent, but it is gener-ally larger and more elongated than in rubicolaand extends further up the body. Frequently, itcan extend to the lower back and then appearsabove the folded wings (plates 115 & 116).

The pattern of the uppertail-coverts andthe size and shape of the white rump patchare valid characters when separating rubicolaand maurus. It is, however, necessary to keepthe potential pitfalls in mind, primarilyfeather wear or damage to the longest upper-tail-coverts of rubicola, leading to the falseimpression that these are entirely white.

Pattern of breast and flanks In typical rubicola, rich, burnt orange-brownfeathering covers the breast and, on mostindividuals, extends onto the belly and flanks(plate 120). In Siberia, from about May toJuly, some worn maurus show a relativelysmall and isolated pale peachy-orange patchin the centre of the breast, comparable to theillustrations in many popular field guides(e.g. Jonsson 1992, Svensson et al. 2010; plate119). In such birds, the breast patch is iso-lated from the black wings by the whiteflanks and breast sides, and the uninter-rupted band of white from the flanks to theneck sides gives them a fairly characteristicappearance. The rest of the underparts aremore or less white (but often retain peachyremnants from fresh plumage). However,many (perhaps even most) maurus exhibit anorange breast-patch that in colour and extentoverlaps with, or even appears more exten-sive than, that of some rubicola. In a fewmaurus, the breast patch is virtually absentand instead replaced by a faint peach hue that varies in extent. Similar patterns were

discussed by Stoddart (2009).In spring and summer, birds from Europe

and Siberia often differ in the pattern of theflanks and belly. The orange-brown flankcolour of many rubicola becomes washed out,with some having an almost soiled-lookinggreyish wash, often with long and thin darkshaft-streaks, which gives them a rather dirtyand untidy appearance. In maurus, most birdsshow clean, fresh and tidy flanks, varying frompure white to peachy orange, depending onwear and the size of the breast patch. This char-acter is often visible from a distance and con-tributes to the first impression of maurus as aclean, handsome, black-and-white bird (plate119). The combined impression of the flanks,belly, breast and neck patches (discussed below)is often the first clue to racial identification.With experience, the distinctive character ofthese smart spring male maurus is not matchedby most rubicola. We believe that the differencesin flank and belly patterns result partly fromthe lack of a pre-breeding moult in rubicola

(which thus has more worn and abraded bodyfeathering compared with maurus), but theremay also be differences in the pattern of thesefeathers; further research is required.

Neck patchesMale rubicola show, on average, smaller whiteneck patches in spring than maurus; intypical individuals these patches appear asthe most striking area of white in theplumage. Seen in profile, the patch appearsisolated between the black head/nape/wingand the brick-rufous breast, often reachingno further than just beyond the wing bend(plate 120). Seen from behind, the neckpatches are separated by a rather wide andsolid black (or with brown feathers admixed)‘bridge’ down the nape.

In classic maurus, the white (or, whenfresh, peachy-ochre) sides of the neck oftenform part of a continuous white areaextending from the flanks, around the wingbend and terminating on the sides of the nape

248



119. (left) Male S. t. maurus/stejnegeri, southwest of Irkutsk, Russia, June 2005. Compare the overallappearance of this bird with the rubicola in plate 120. ‘Classic’ male maurus differ from male rubicolaby the smaller and paler breast patch (with a peachy hue), the white neck patches that extend ontothe side of the nape, and the clean, white flanks that bleed into the belly. Although these are ‘soft’characters, the resulting impression is of a crisp, clean and rather handsome bird.

120. (right) First-summer (2CY) male S. t. rubicola, Istanbul, Turkey, June 2010. A rather typical birdwith a rich, burnt-rufous breast. Note the isolated white neck patch that stands out as the singlepalest area of the bird, reaching onto the side of the neck just beyond the wing bend. Furthermore,the lower flank and belly are worn and show thin (but rather long) dark shaft-streaks just above thelegs, which is characteristic of rubicola. Aged as 2CY by the contrast between the retained juvenilealula, primary coverts, primaries and secondaries, and the darker first-winter wing-coverts acquiredduring the post-juvenile moult.

Magnu

s Hellström

Volkan

Donba

loglu

where they form a half-collar. Inthe most extreme cases thesepatches can appear to meet on thenape but there are always somedark feathers in the ‘bridge’between crown and mantle. Thisbridge is often colder in tone thanon rubicola, often greyish-black(rather than brownish-black), andsometimes with white feathersadmixed. There is extensive overlap,however, and individuals thatexhibit a pattern similar to that ofrubicola are commonly seen.

Note also that the neck pattern isaffected by posture, and a tiltedhead might temporarily create amisleading appearance. However, ifthe pattern is observed with the birdin a fairly neutral resting position, itmay provide a useful contributingcharacter for racial identification,especially when faced with the mostextreme pattern of some maurus. Wider napebridges are found in both subspecies, and byitself this is not a valid character (plate 121).

Racial identification of femalesWhen identifying females during spring,attention should focus primarily on the

appearance of the rump/uppertail-covertsand throat/chin, but the general colorationand the pattern of the neck sides can alsoprovide some guidance. Unlike males,females of all forms show a similar under-wing pattern and this is of no value in identi-fication (plates 122 & 123).



122. (left) Female S. t. maurus, southwest of Irkutsk, Russia, June 2008. Unlike eastern males, easternfemales show grey underwing feathers with pale edges. Western females show a similar pattern andwe have not found any useful racial difference in the coloration of the underwing.

123. (right) Female S. t. rubicola, Israel, January 2010. Note the similarity in underwing patternbetween this female rubicola and the female maurus in 122.

Joha

n Stenlund

Shraga Alon

121. Specimens of male S. t. maurus (collected in summerand held at ZMUC, Copenhagen), western Siberia, Russia.Note the variation in the width of the dark ‘bridge’connecting the black head with the mantle.

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s Hellström

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Overall colorationAs spring progresses, the effects of wear resultin female maurus becoming darker above,while the breast and belly lighten, thoughoften retaining a slight peachy hue. Together

with the pale face, throat and rump, this oftengives female maurus a generally pale impres-sion, with contrastingly darker upperparts(plates 124 & 125). Western birds typicallybecome darker overall, but usually retain a

124. Female S. t. maurus, Altai, Russia, July 2007. Note the pale face and throat as well as the palepeachy underparts (cf. the deeper orange cast shown by most rubicola). The contrast between thepale crown and the darker nape is probably due to an incomplete pre-breeding moult of the head,only the front part having been moulted.

Matthieu Vaslin

125. Female S. t. maurus, Alakol, Kazakhstan, June 2006. A typical eastern female in spring with apale face, throat and underparts contrasting with the dark upperparts. Note that the visible rumpfeathers are white.

Anders Blomdahl

deeper orange cast to the underparts. Insummer, many western females show adark grey throat and whitish neckpatches set off against a dull or draborange-toned breast (plates 127 & 129).

Rump and uppertail-covertsFemale rubicola has a rather dark andoften rich-brown rump and uppertail-coverts with distinctive dark streaking,and this shows little contrast with therest of the upperparts (plate 127). Wehave not encountered any westernfemales that lack this dark streaking orshow a white basal colour to the rumpor uppertail-coverts.

Unlike rubicola, maurus has a rela-tively large and unmarked rump patch,which ranges from deep sand or ochreto whitish, and which usually contrastswith the darker back. Many femalemaurus in our sample from May andJune showed a predominantly whiterump, especially the lower rump anduppertail-coverts, which can appearpure white. Some females show plainochre rump feathers while others have anochre tone to the feather centres only, givinga pale, speckled appearance. Rarely, the shaftsof the rump feathers can be quite greyish and

may give a thinly streaked appearance butthis should not be confused with the bolderpattern of western races (plate 126).

In summary, although some maurus may



127. Female S. t. rubicola, Holland, March 2008. A typical female rubicola in early spring. The throat is still pale but some dark spots are beginning to appear. This bird’s throat will, with wear, probablyget darker as spring progresses. A few western females may not get much darker than this, whileothers can appear almost as black-chinned as males. Note the orange rump, breast, belly and ventand the distinct dark markings on the uppertail-coverts.

Arie O

uwerkerk

126. Female S. t. maurus, Eilat, Israel, March 2005. The relatively large ochre-and-white rump and uppertail-coverts contrast well against the darker back. Note thatthis individual shows darker shafts on the rump feathers,which give the rump a thinly streaked appearance, althoughthese are not comparable with the bolder dark markingsshown by the western races. Note the pale ‘open’ face and underparts, and lack of white neck patches.

Tommy Holmgren

have a relatively dark ochre rump which con-trasts less with the back (and may then beslightly more difficult to distinguish fromsome western females), the rump pattern as awhole is an important and reliable characterfor identification.

Throat and chinThe female throat pattern is rather variableand during autumn both European andSiberian birds often show a buffish-white orgreyish-white throat. By spring, most femalerubicola have developed a darker (sometimesblackish) throat, while in maurus this usuallyvaries from dirty white to pure white. Somesources (e.g. Svensson et al. 2010) state thatthe throat of eastern females never gives adark impression. While this is true for thevast majority, a few eastern females can showrelatively extensive dark markings on thethroat – especially along the lower edge andin the malar region. In a couple of instanceswe found this to be more extensive and remi-niscent of female rubicola (see plate 128).

Neck patchesFemale rubicola and maurus show neck patchesof varying prominence, but variation tends tobe greater in rubicola – from complete absenceto a pure white neck patch. However, any whitepatches are rather restricted and rarely take theform of a neck collar (cf. males). Converselymaurus shows, on average, slightly wider andbrighter (greyish to white) neck patches that

may give the impressionof a pale collar, thoughoften rather diffuse.Owing to the overall palerappearance of maurus,this pattern is generallyless prominent or contrasting, and manyeastern females show onlya vaguely brighter side ofthe neck.

SuperciliumCramp (1988) indicatedthat typical maurus has amore prominent palesupercilium than rubi-cola. In some easternfemales the supercilium

is quite distinct throughout its length(including the forehead) but in our samplefemales showed considerable variation withinboth races; only the presence of bright anddistinct supercilia can be used to supportidentification as maurus. In relation to theimportance of the rump, throat and generalcoloration, the supercilium should beregarded as a supplementary character only.

Birds from southern ItalyDel Hoyo et al. (2005) stated that ‘Birds onSicily… most closely resemble maurus(hence, a challenge to the splitting of thelatter)…’, and a description of maurus-likebirds breeding on Sicily was given by Corso(2001). We agree that a small proportion ofrubicola (perhaps especially in Italy, but alsoelsewhere) can appear very similar to maurusand, at times, characters such as the patternof breast, flank, neck and rump are surpris-ingly similar to typical Siberian birds. In ouropinion, however, these birds represent oneextreme of the continuous variation thatexists within rubicola. Safe identification of adifficult bird relies entirely on the patternand colour of the underwing and the (fresh)uppertail-coverts. With this in mind, photo-graphs of Sicilian birds we have studied haveshown nothing that would group these birdscloser to maurus than to rubicola. At present,we do not consider that the appearance ofbirds breeding in Sicily should be used tocloud this discussion.

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128. Female S. t. maurus, Altai, Russia, July 1926 (specimen held atZMUC, Copenhagen). Occasionally, some worn eastern females show a relatively dark throat – as in this case, where the lower throat seemsparticularly dark. In this specimen, however, the dark impression isperhaps slightly exaggerated by the position of the head, which ispushed back, exposing the darker feather bases.

Magnu

s Hellström



ConclusionsThere are a number of characters separatingrubicola and maurus but, owing to the exten-sive variation shown in both taxa, several ofthese should be regarded as supportive ratherthan confirmative. Two such characters – thepattern of the breast and the size of the neckpatches – are often described in the literature,but in our opinion the colour, pattern andstate of the flank and belly feathering gives abetter guide in most individuals. The patternof the underwing in males and the pattern offresh uppertail-coverts (in both sexes) arediagnostic, but not always easy to assess. Withcare, rubicola and maurus can be reliably sep-arated in the field in the vast majority ofcases

Acknowledgments

We would like to thank Jon Fjeldså and Jan BoldingKristensen at the Zoological Museum, Copenhagen, aswell as Göran Frisk and Peter Nilsson at the Museumof Natural History, Stockholm, for generous access totheir collections. Finally, we are greatly indebted to allthe photographers who provided us with referenceimages (only a small number of which are publishedhere).

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ittingen

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Magnus Hellström, Ottenby Bird Observatory, Ottenby 401, S-386 64 Degerhamn, Sweden; e-mail [email protected]

Mats Wærn, Carl Malmstens Väg 21, S-386 93 Färjestaden, Sweden; e-mail [email protected]

Magnus Hellström is a biologist and agronomist who works for the Swedish Ornithological Society as the headof Ottenby Bird Observatory, on Öland, southeast Sweden. He is also Chairman of the Swedish RaritiesCommittee and a tour leader for AviFauna. Mats Wærn is a biologist (eco-toxicologist) who works as anenvironmental consultant in Kalmar, southeast Sweden. He is Secretary of the Swedish Rarities Committee andhas travelled extensively in the Western Palearctic, Middle East and southern Russia.

Documents

Field identification and ageing of Siberian Stonechats in ... · variability within and between these races is discussed, and some gaps in our knowledge of Siberian birds are addressed