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230 [Dutch Birding 45: 230-239, 2023]
The identification headache of separating males
Eastern Black Redstart Phoenicurus ochruros
phoenicuroides/murinus from hybrid males (West-
ern) Black x Common Redstart Pochruros x phoe-
nicurus has previously been dealt with by Steijn
(2005) and van der Spek & Martinez (2018). Since
the latter paper was published, many more hybrids
have been photographed. This allowed us to test
our initial findings on both plumage characters
and temporal distribution based on a much larger
dataset. Furthermore, we gained insights in the vo-
calisations of hybrids (Martinez et al 2019) and
Black Redstart taxa (Martinez & van der Spek
2022). This paper summarises the current state of
aairs regarding the identification of vagrant
Eastern Black in Europe. Calls might form a key to
at least identify candidate Eastern Black in female-
type plumages, which so far have stayed under the
radar due to a lack of identification features. We
also gained more insights in the whereabouts of
hybrids in winter, and learnt more about Western
Black Redstarts Po gibraltariensis with extended
red or orange on the underparts.
Methods
In van der Spek & Martinez (2018), we analysed
photographs of 62 hybrid males (Western) Black x
Common Redstart and 50 males Eastern Black
Identification of Eastern Black
Redstarts – an update
Vincent van der Spek & Nicolas Martinez
278 Eastern Black Redstart / Oosterse Zwarte Roodstaart Phoenicurus ochruros phoenicuroides/murinus, first calen-
dar-year male, Rolde, Drenthe, Netherlands, 10 November 2012 (Garry Bakker). Classic vagrant immature male as
they turn up in north-western Europe. Note following characters: A(very) little white on forehead; Bneat, oval shaped
blackish breast-patch with deepest point in centre; Corange triangular shaped patch between blackish breast-patch
and wing, solid feature for Eastern Black males; Dunderparts mostly solid orange, no black spotting or streaking on
belly or flank, no large pure white band reaching upper belly and breast; Eundertail-coverts slightly paler orange but
not (nearly) white as in some hybrids; Fno white wing-panel.
231
Identification of Eastern Black Redstarts – an update
Redstart found on the internet and in journals.
There, we formulated a set of plumage characters
that, especially when used in combination, al-
lowed virtually all birds to be identified (plates
278-280). These plumage traits were divided over
two categories, with 1diagnostic features, and
2supporting but not (fully) diagnostic features. For
the full set of characters, see van der Spek &
Martinez (2018). When analysed thoroughly, truly
‘problematic’ birds (ie, individuals that could not
be identified with certainty) proved to be very rare.
Furthermore, an analysis of the temporal distribu-
tion showed that hybrids were found between
early spring and early autumn, whereas nearly all
vagrant Eastern Black in Western Europe were
found during late autumn and sometimes winter:
overlap between the two was close to non-exist-
ent. For a more comprehensive description of the
methods, see van der Spek & Martinez (2018).
However, would our criteria still stand when a
larger dataset was used? Up until December 2022,
we collected data of another 152 hybrid males,
mainly while doing research for related papers
(Martinez et al 2019, Martinez & van der Spek
2022), but also because observers sent us photo-
graphs to judge.
Hybridisation experiments in captivity provided
useful insights in the phenotypes of hybrids (cf
Nicolai et al 1996, Martinez et al 2019). Based on
these results, we considered individuals to be the
result of introgression if one or more plumage and/
or structural features were either intermediate be-
tween the two species, or if a bird showed features
of both parental species (based on the generally
accepted plumage variation in the parental species
described in identification literature). In virtually
all birds that we considered to be of hybrid origin
that were either trapped, or photographed really
well, we noted more than one ‘mixed’ feature
(with ‘red-bellied’ Western Black Redstart being
the major exception), not only in plumage but also
including birds with an intermediate wing formula
279 Hybrid Black x Common Redstart / hybride Zwarte x Gekraagde Roodstaart Phoenicurus ochruros x phoenicu-
rus, adult male, Limassol, Cyprus, 15 February 2022 (Stavros Christodoulides). This bird combines many hybrid
features and is, like majority of all hybrids, straightforward to separate from Eastern Black Redstart Po phoenicu-
roides/murinus after analysis by combination of: Aabsence of invariably orange triangular shaped patch of Eastern
Black between breast-patch and wing (grey here, if dark markings present can also be black or partially black/grey
mixed with orange in hybrids, although some completely orange, as in Eastern Black); Blarge white wing-panel
(matching Western Black Redstart Po gibraltariensis); Crectangular, messy breast-patch instead of rounded and clear
cut as in Eastern; Dgrey on flank (if present sometimes black in hybrids; invariably orange in Eastern Black); Epalish
orange underparts with greyish spots (invariably deep orange in Eastern Black, without grey or black). These features
are all diagnostic. White on forehead and supercilium matches Common Redstart Pphoenicurus rather than Eastern
Black but not extremely large in this bird. Undertail-coverts palish orange but perhaps not outside range of Eastern
Black. If (merely) white, it is very useful hybrid feature.
232
(Steijn 2005; 22%) and mixed or intermediate vo-
calisations (see below; 6%). This allowed us to in-
crease our initial dataset and test our findings on a
total of 214 hybrids (including potential or ‘red-
bellied’ Western Black; see results). Furthermore, a
study on vocalisations of the entire Black Redstart
complex (Martinez & van der Spek 2022) provided
a new tool for the identification of Eastern Black:
the contact call. Frequencies and lengths were
measured on sonagrams and shapes of calls were
analysed. For a more comprehensive description
of the methods, see Martinez & van der Spek
(2022). For the present paper, we have tested our
findings in the latter study on vagrant Eastern Black
observed in western Europe. Note that we do not
deal with the separation of Common Redstarts
Pphoenicurus and hybrids here, which will be
dealt with extensively in a separate paper (Martinez
2023).
Identification of vagrants by plumage
The analysis confirmed the results of the 2018
publication (table 1), with more than 90% of all
analysed hybrids showing diagnostic category 1
features and/or several category 2 features. The
proportion of potentially problematic hybrids was
slightly higher than in the 2018 sample (7.9% ver-
sus 4.8%) but still well below 10%. Most impor-
tantly, only one additional Eastern Black Redstart
look-alike with good photographic material was
found, for which only the wing formula proved a
hybrid origin (plate 280). We here nuance one cat-
egory 1 feature from van der Spek & Martinez
(2018) as diagnostic for a hybrid, namely an or-
ange belly that is ‘split’ into two halfs by a large
white band. Since we found three examples of
Eastern Black on the breeding grounds with bellies
approaching this pattern, we here transfer this fea-
ture to category 2 (‘suggestive’ of a hybrid). It is,
however, fairly unusual in Eastern Black.
Temp ora l di st ri bu ti on o f hy br id s an d va gran ts
In van der Spek & Martinez (2018), we showed
that nearly all vagrant Eastern Black Redstarts in
Europe were found between mid-October and
March (by far most in mid-October to November),
whereas certain hybrids (see below) were found
between March and early October (by far most in
April-July). Their occurrence was thereby virtually
separated in time, which provided useful ‘circum-
stantial evidence’ for their identification. A slightly
complicating factor was the occurrence of Western
TABLE 1 Identification of male hybrid Black x Common Redstart Phoenicurus ochruros x phoenicurus relating to
Eastern Black Redstart Po phoenicuroides/murinus (here phoenicuroides) based on plumage features from van der
Spek & Martinez (2018) (n=214)
2018 new combined
Diagnostic category 1 features clearly n=57 n=126 n=183
proving hybrid origin
Combination of category 2 features n=1 n=13 n=14
strongly indicating hybrid origin
Hybrids that should not be problematic n=58 93.5% n=139 91.4% n=197 92.1%
Apparent phoenicuroides look-alikes n=1 n=4 n=5
(only one very subtle diagnostic category 1
feature proves hybrid origin)
Apparent phoenicuroides look-alikes n=1 n=2 n=3
with one category 2 feature, either
indicating hybrid origin or leaving bird
unidentified
Apparent phoenicuroides look-alikes but n=1 n=6 n=7
photographic material insucient to judge
more features
Potentially problematic birds n=3 4.8% n=12 7.9% n=15 7.0%
Phoenicuroides look-alikes with good n=1 n=1 n=2
photographic material
Problematic birds n=1 1.5% n=1 0.7% n=2 0.9%
Total n=62 100% n=152 100% n=214 100%
Identification of Eastern Black Redstarts – an update
233
Identification of Eastern Black Redstarts – an update
280 Hybrid Black x Common Redstart / hybride Zwarte x Gekraagde Roodstaart Phoenicurus ochruros x phoenicu-
rus, first calendar-year male, Mandria, Cyprus, 3 December 2011 (Stavros Christodoulides). This was with certainty
most problematic individual to separate from Eastern Black Redstart Po phoenicuroides/murinus in new dataset. This
bird lacks diagnostic hybrid plumage features but wing formula proving hybrid origin. Vent and undertail-coverts on
pale end for Eastern Black, and some grey is interspersed on not very deeply orange underparts. Perhaps breast-patch
is slightly too large and not rounded enough but it is all very subtle. Such hybrids really are exceptional. Both this
bird and one in plate 279 are also very interesting concerning whereabouts of hybrids in winter.
Black Redstarts with a (partially) reddish or orange
belly, that otherwise showed no hybrid features.
These are being dealt with separately below.
Western Black often do have some reddish orange
extending slightly from the undertail-coverts to the
vent but what is the variation, and when is the red/
orange too extended to still label a bird as pure?
Intriguingly, birds labelled in this category were
the only potential (uncertain) hybrids that were
seen during winter. The enlarged dataset largely
confirmed our initial findings. However, some nu-
ances should be mentioned. Common Redstarts
are long-distance migrants that are rare to even
extremely rare in Europe from November to
February, whereas Western Black are short-dis-
tance migrants. Based on scant evidence, we hy-
pothesised in Martinez et al (2019) that hybrids
have an intermediate migration strategy and may
winter in the southern Mediterranean. Since then,
we indeed found several sightings of wintering
birds in north-western Africa and the southernmost
parts of Europe (including Mediterranean islands).
The occurrence in these regions is even inverted,
with most hybrids being seen in autumn and win-
ter rather than in the breeding season (figure 1).
This seems to confirm our hypothesis that hybrids
are medium-distance migrants. Hence, the picture
painted of hybrids not being present in winter was
firmly confirmed for large parts of Europe (central,
northern and north-western) but not for the
Mediterranean: care is still needed when a poten-
tial Eastern Black is seen there in late autumn or
winter. We also confirmed the presence of ‘red-
bellied’ Western Black in winter, also in the north-
ern half of Europe (see discussion).
Calls of hybrids and vagrants
In Martinez & van der Spek (2022), we analysed
the contact calls of five out of six Black Redstart
taxa (we were unable to obtain recordings of the
Levantine subspecies Po semirufus). We found
three ‘call groups’: 1the first call group (vist) is
formed by the western subspecies gibraltariensis
breeding in Europe (including aterrimus that is not
acknowledged by the International Ornithological
Committee, cf Gill et al 2023), the morphologi-
cally intermediate subspecies ochruros from the
Middle East, and Eastern Black Redstarts of the re-
cently described subspecies murinus from Mon-
golia and the Altai (formerly regarded as the north-
ern populations of phoenicuroides; Fedoren ko
2018). See discussion below on the validity of the
234
1 2 3 4 5 6 7 8 9 10 11 12
month
45
40
35
30
25
20
15
10
5
0
records
hybrids in southern Europe and North Africa
red-bellied Black Redstarts in southern Europe and North Africa
red-bellied Black Redstarts in central and northern Europe
hybrids in central and northern Europe
FIGURE 1 Temporal distribution of hybrids Black x Common Redstart Phoenicurus ochruros x phoenicurus (n=219) as
well as ‘red-bellied Black Redstarts’ Pochruros (n=26) in Europe and North Africa per 10-day period. Birds from loca-
tions south of a line from Barcelona, Spain, Roma, Italy, and Sofia, Bulgaria, grouped under southern Europe and
North Africa.
name for this new taxon. 2Further south-east, an-
other call group (heed) is formed by what was until
recently regarded the southern range of phoenicu-
roides. On average, this group calls at lower fre-
quencies and within a smaller frequency range.
3The third group (tiut) is formed by the eastern
subspecies rufiventris which diers markedly from
all other taxa, with a descending instead of a rising
call, given at much lower frequencies. Within the
first group, average dierences also exist between
taxa, with murinus on average producing lower-
pitched calls than the other taxa in the group.
However, note that there is overlap with c10% of
gibraltariensis (including ‘aterrimus’ from Portugal
and central and southern Spain that is usually in-
cluded in gibraltariensis, but see discussion) giving
calls with a maximum frequency below 5300 kHz
(Martinez & van der Spek 2022). Calls consistently
below 5100 kHz are however very suggestive of
an eastern origin, with none of the analysed gibral-
tariensis and ochruros (except for birds from Iran)
and only three ‘aterrimus’ showing such low-
pitched calls (n=201 birds; Martinez & van der
Spek 2022). Based on these findings, the analysed
calls of five vagrants from north-western Europe
fall into call group 1 and do not match any of the
other eastern taxa. Unsurprisingly, within this
group they best match the calls of birds from the
Altai and Mongolia better than any of the western
taxa (figure 2-3). A bird observed in Groningen,
the Netherlands, in 2018 mostly called like a
‘northern’ Eastern Black Redstart but additionally
produced a few calls that were more reminiscent
of birds from the southern phoenicuroides group
(figure 2). Clearly, none of the calls of these five
vagrants approached rufiventris. We also analysed
the calls of 11 hybrid Black x Common Redstarts
(including two mixed singers, see Martinez et al
2019). These birds showed calls typical of the
Western Black Redstart group, in sound, shape
and frequencies (figure 2-3). Furthermore, at least
six also gave Common Redstart-like calls. It is typ-
ical for hybrids to switch between call types of
their parental species (Martinez et al 2019).
Finally, one bird gave some calls that seemed to be
intermediate between the two species, approach-
ing those of Eastern Black (figure 4).
Identification of Eastern Black Redstarts – an update
235
Identification of Eastern Black Redstarts – an update
Discussion
Identification on plumage
The plumage traits that we proposed to separate va-
grant Eastern Black Redstarts from hybrids Black x
Common Redstart (van der Spek & Martinez 2018)
have been confirmed by a dataset that was nearly
four times as large as in the original paper. We
therefore consider our findings robust. Despite be-
ing only a very small minority, we however (again)
note that, very occasionally, hybrids occur that are
doppelgangers of Eastern Black. The wing formula
(Steijn 2005) is crucial for the identification of such
birds, as are their calls (see below). Most hybrids in
the dataset are from spring and summer. With hy-
brids being so rare in autumn in Europe, we have
found few examples of first-winters. In theory, the
number of birds that are dicult to identify (as in
plate 280), could be higher among first calendar-
year hybrids in autumn than among spring birds.
Temp or al d ist ri bu ti on
For the northern half of Europe, we confirm that the
timing of a sighting between late autumn (mid-Oc-
tober) and winter (mid-February) can be used as
‘circumstantial evidence’ for the identification:
during this time of year, it can be safely assumed
that birds that look like Eastern Black, indeed are.
In the new dataset, we found supporting evidence
for the suggestion in Martinez et al (2019) that is in
line with the results of extensive experiments in avi-
aries in the 1990s by Berthold & Querner (1995).
Hybrids indeed seem to be middle-distance mi-
grants that have an innate (‘hybrid’) migration strat-
egy and overwinter in the southern Mediterranean.
In southern Europe, the temporal distribution can
therefore not be used as supporting evidence.
‘Red-bellied Western Black Redstarts’
In van der Spek & Martinez (2018) and Martinez et
al (2019), we suggested that one aberrant type of
redstart could in fact be a variant within Western
Black Redstart with more orange on the belly than
usual, rather than a hybrid (plate 281-282). The
phenology of these birds seems to confirm this hy-
pothesis, since they do not show the migratory be-
haviour of hybrids. ‘Obvious’ hybrids are not pre-
sent in winter in most of Europe, while ‘red-bellied
Western Black are (just like ‘normal’ Western
Black). Hence, their behaviour does not match the
hypothesis of hybrids that have a medium-distance
migration strategy. Finally, they do not seem to
show other hybrid features. We therefore conclude
that these birds are likely not the result of (recent)
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 s
1 2 3 4 5 6 7 8 9 10 11 12 13
kHz7
6
5
4
3
2
1
0
murinus
(Russian Altai, Mongolia)
Eastern Black Redstart
(vagrants western Europe)
hybrids
Black x Common Redstart
FIGURE 2 Calls from Eastern Black Redstarts Phoenicurus ochruros murinus from Altai and Mongolia (birds 1-5), from
vagrant Eastern Black Redstarts Po phoenicuroides/murinus observed in western Europe (recording 6-10, whereas
recording 9-10 are from the same bird) and from hybrids Black x Common Redstart Pochruros x phoenicurus (bird
11-13). 1Siberia, Russia, 24 June 2010 (Antero Lindholm; https://xeno-canto.org/158171), 2(VPAV77651),
3(VPAV215085), 4Mongolia, summer 2021 (Jugdernamjil Nergui), 5Mongolia, 6 June 2013 (Patrick Franke, https://
xeno-canto.org/162680), 6Netherlands, 4 December 2017 (Marc Plomp), 7Britain, 1 December 2014 (Birding-
frontiers), 8Netherlands, 8 November 2012 (Sander Bot; https://xeno-canto.org/112455), 9-10Groningen,
Netherlands, 10 March 2018 (Marnix Jonker; https://waarneming.nl/sounds/66734), 11Czechia, summer 2019 (Filip
Petřík), 12Germany, 12 June 2018 (Ralph Martin, https://xeno-canto.org/548970) and 13Switzerland, 2 April 2020
(Nicolas Martinez; https://xeno-canto.org/540835). For VPAV recordings, contact Olga Veprintseva via https://tinyurl.
com/y3vu5yd3.
236
FIGURE 3 Outlines of plotted minimum and maximum frequencies for dierent Black Redstart Phoenicurus ochruros
populations and subspecies (from Martinez & van der Spek 2022), complemented with corresponding values for five
vagrant Eastern Black Redstarts Po phoenicuroides/murinus and 11 hybrids Black x Common Redstart Pochruros x
phoenicurus (including two mixed singers). One hybrid giving few calls seemingly intermediate between both spe-
cies and approaching calls of Eastern Black marked with both diamond and triangle, al other birds represented with
one dot only. Countries indicated by their ocial ISO-3166 three-letter codes.
rufiventris (CHN)
rufiventris (IND)
phoenicuroides/rufiventris (AFG, SE KAZ, KGZ, TJK, UZB)
murinus (Altai, MNG)
ochruros (Caucasus, TUR)
ochruros/phoenicuroides (IRN, SW TKM)
gibraltariensis
aterrimus (ESP, PRT)
Eastern Black Redstart vagrants western Europe (n=5)
hybrids Black x Common Redstart and mixed singers (n=11)
Göttingen 2019
Groningen 2018
Hz6500
6000
5500
5000
4500
4000
max frequency
3000 3500 4000 4500 5000 5500
max frequency
FIGURE 4 Examples of calls of hybrid Black x Common Redstart Phoenicurus ochruros x phoenicurus from Göttingen,
Niedersachsen, Germany, in 2019 (based on recordings from Martin Göpfert). First two calls corresponding with
Common Redstart Pphoenicurus, call 4 and 6 typical Western Black Redstart Po gibraltariensis calls. Call 3 and 5,
however, approaching those of Eastern Black Redstart Po phoenicuroides. Note that vast majority of calls of this bird
were normal Western Black calls.
Identification of Eastern Black Redstarts – an update
kHz7
6
5
4
3
2
1
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6s
1 2 3 4 5 6
237
Identification of Eastern Black Redstarts – an update
281-282 Western Black Redstart / Westelijke Zwarte Roodstaart Phoenicurus ochruros gibraltariensis, adult male,
Helgoland, Schleswig-Holstein, Germany, 11 April 2015 (Jochen Dierschke). Amount of red on underparts is only
aberrant feature compared with what is regarded ‘normal’ for Western Black. Other plumage features, as well as wing
formula and temporal distribution are identical to Western Black, leading to conclusion that these type of birds
represent variation within Western Black rather than being result of (recent) hybridisation between Western Black and
Common Redstart Pphoenicurus.
238
hybridisation. It is of course not excluded that
these birds are backcrosses (F2+), or that it is even
an old ancestral trait.
Calls
Analysis of the few calls recorded of vagrant
Eastern Black Redstarts in Europe strongly support
an origin from the northern parts of the range, from
the area where the populations are now named
murinus. Note, however, that birds from northern
Iran and adjacent western Turkmenistan have calls
similar to murinus (Martinez & van der Spek 2022),
though these populations are believed to be altitu-
dinal or short-distance migrants at most (Cramp
1988, Clement & Rose 2015), making a (regular)
appearance in western Europe highly unlikely.
Calls can therefore also be used as an additional
identification feature in a vagrant context (Martinez
& van der Spek 2022). Eastern Black will, on aver-
age, produce lower-pitched calls than Western
Black Redstart. The frequencies of Eastern Black
from the north of their range clearly dier in mean
values from Western Black. Calls consistently be-
low 5100 kHz are very suggestive of an eastern
origin. Hybrids Western Black x Common Redstart
can produce both Western Black and Common
Redstart type calls (Martinez et al 2019). If a bird
calls like a Common, or combines calls of both
Western Black and Common, this will rule out
Eastern Black. An eastern vagrant will, on average,
give lower-pitched calls than a hybrid with Western
Black. Be aware that, though rarely, calls interme-
diate between Common and Western Black also
occur in hybrids and that these can strongly resem-
ble the call of Eastern Black from the northern part
of the range. Therefore, typical high-pitched West-
ern Black (gibraltariensis) calls help to rule out a
vagrant Eastern Black and point towards a hybrid,
whereas low calls are certainly supportive but they
do not necessarily diagnostically rule out a hybrid.
It is therefore also important to try and obtain re-
cordings with a longer series of calls of a potential
vagrant, thus avoiding the identification being
based on single calls that may not be typical for the
specific individual. Furthermore, calls should assist
in searching for candidate Eastern Black among fe-
male types (including the ‘carei’ morph of imma-
ture males that look like females; cf Nicolai et al
1996), that now remain completely undetected
since identification on plumage has so far been im-
possible (Shirihai & Svensson 2018, van Duivendijk
& Guyt 2022). Given the number of males, such
birds must also turn up in Europe. Low ‘vist’ con-
tact calls given by a suitable looking female-type
bird are certainly a supporting character.
Validity of murinus and aterrimus
Our analysis of the call groups provides supporting
evidence that indeed two subspecies of Eastern
Black Redstart are involved in what was tradition-
ally known as phoenicuroides. We therefore do
not question the validity of murinus as a newly de-
scribed subspecies but we do argue that the cho-
sen name for it is a junior synonym of phoenicu-
roides. The original description of the holotype of
phoenicuroides (Moore 1854) mentions ‘crown,
neck, back and upper wing-coverts ash, with a ru-
fous tint, the ash palest on the crown’, matching
exactly what is distinctive about murinus. This was
acknowledged by Fedorenko (2018) but he argued
that the holotype was collected on 21 March 1852
in Pakistan in the presumed wintering quarters and
that therefore its breeding grounds are unknown.
That might be true but, based on plumage, we ar-
gue that the phoenicuroides holotype is likely to
belong to the northern population of Eastern Black.
We are therefore hesitant to employ a new name
for these birds and actually believe that birds from
the Altai and Mongolia should still be named
phoenicuroides. As a consequence, it is the south-
ern population (now named phoenicuroides) that
requires a new name (Martinez & van der Spek
2022). While aterrimus is mostly regarded a syno-
mym of gibraltariensis, apart from subtle plumage
dierences between males, calls are an additional
argument to regard it as a valid subspecies.
Although belonging to the same call group, aterri-
mus tends to have slightly lower-pitched calls than
gibraltariensis (Martinez & van der Spek 2022).
Call for assistance
We invite anyone with the possibility of obtaining
recordings of semirufus (western Syria, Lebanon
and north-eastern Israel, and possibly northern
Iraq and extreme southern Turkey bordering Syria)
to do so and to share these with us, so we can de-
termine in which call group this subspecies be-
longs, or to perform and publish a similar analysis.
Acknowledgements
We would like to thank all observers that sent us photo-
graphs and sound-recordings of hybrids as well as va-
grant Eastern Black Redstarts, or made them available on
public internet databases (especially eBird, Macaulay
Library, www.observation.org and several ornithological
platforms). The following persons shared several new ob-
servations of hybrids with us and discussed identification
details: Stavros Christodoulides, Jochen Diersch ke (both
also kindly allowed us to use their photographs), Andrea
Corso, Guillermo Rodriguez Lazaro, Magnus Hell ström,
Martin Göpfert, Filip Petřík and Hugo Touzé.
Identification of Eastern Black Redstarts – an update
239
Identification of Eastern Black Redstarts – an update
Samenvatting
HERKENNING VAN OOSTERSE ZWARTE ROODSTAARTEN – EEN UPDATE
Het onderscheid tussen enerzijds mannetjes Ooster se Zwarte
Roodstaart Phoenicurus ochruros phoenicuroides/murinus
die als dwaalgast in Europa komen en anderzijds hybride
Zwarte x Gekraagde Rood staart Pochruros x phoenicurus is
in diverse artikelen behandeld. Hier worden eerder geformu-
leerde kleed kenmerken getoetst op een aanmerkelijk grotere
dataset van hybriden, die daarnaast ook meer inzicht biedt in
de fenologie. Daarnaast is er inmiddels meer kennis over ver-
schillen in contactroepen van zowel hybriden als verschil-
lende populaties van Zwarte Roodstaarten. De inmiddels be-
kende kleedkenmerken zoals geformuleerd in van der Spek &
Martinez (2018) houden nog steeds stand. Nagenoeg alle
vogels zijn daarmee bij nadere bestudering op naam te bren-
gen. Dubbelgangers, die alleen met zekerheid te determine-
ren zijn op basis van verschillen in de vleugelformule, blijven
extreem zeldzaam. Voor de noordelijke helft van Europa is
ook bevestigd dat er geen hybriden tussen half oktober en
half februari zijn waargenomen, terwijl juist in die periode
nagenoeg alle Oosterse Zwarte als dwaalgast in Europa zijn
gezien. Deze scheiding in fenologie is zo strikt dat het als
ondersteunend determinatiekenmerk kan worden gebruikt.
Voor h et Me diterrane geb ied g aat dit e chter niet op. Da ar
worden in de winterperiode zelfs meer hybriden gezien dan
tijdens het zomerhalfjaar. Dit bevestigt een eerdere theorie
dat hybriden een intermediaire trekstrategie hebben. Ge-
kraag de Roodstaart Pphoenicurus is een langeafstan dstr ekke r
en Zwarte een korteafstandstrekker, en hybriden lijken over
middellange afstanden te trekken. Eén afwijkend type rood-
staart, in eerdere artikelen als ‘onzekere’ hybride beschreven,
wordt ’s winters wél in de noordelijke helft van Europa ge-
zien. Dat zijn vogels die eruit zien als Zwarte Roodstaart,
maar die meer roodoranje op de onderdelen hebben dan
gebruikelijk. De vraag was of dit extreme variatie is van
Zwarte, of een teken van hybridisatie. Het feit dat deze vogels
wél in de winter aanwezig zijn in noordelijk Europa (in tegen-
stelling tot alle zekere hybriden), en zich dus niet gedragen
als hybriden door over middellange afstand weg te trekken,
plus het feit dat ze geen andere ‘typische’ hybridekenmerken
vertonen, versterkt het beeld dat dit geen (eerste generatie)
hybriden zijn, maar variatie representeert binnen Westerse
Zwarte Roostaart. Of er sprake is van hybridisatie die langer
geleden plaatsvond (backcross F2+), of dat zelfs heel ‘oude
genen’ van voorouders (incidenteel) nog zichtbaar worden in
fenotypen, is niet geheel uitgesloten.
Inmiddels is er inzicht in gemiddelde verschillen in de
contactroepen van Zwarte Roodstaarten. De roep van Ooster-
se Zwarte Roodstaarten in Europa komt overeen met die van
noordelijke populaties, een sterke aanwijzing voor de her-
komst van deze dwaalgasten in Europa. Ze roepen niet alleen
anders dan andere taxa van Oosterse Zwarte (met zelfs een
sterker verschil dan met Westerse Zwarte Roodstaart), ze roe-
pen gemiddeld ook lager dan Westerse Zwarte. Er is wel over-
lap maar roepjes die structureel lager zijn dan 5100 kHz zijn
zeer suggestief voor een noordoostelijke herkomst, en uitzon-
derlijk voor Westerse Zwarte. Hiermee kunnen op basis van
opgenomen roepjes ook ‘kandidaat’ Oosterse Zwarte onder
nu niet te determineren vrouwtjes-type exemplaren worden
herkend. Hybriden roepen vaak afwisselend als Westerse
Zwarte en Gekraagde Roodstaart. Sommige individuen kun-
nen roepjes produceren die daar tussenin zitten en daarmee
op Oos ter se Zwarte lijken. Het is daarom raadzaam een serie
roepjes op te nemen, want een hybride zal zich uiteindelijk
waarschijnlijk ‘verraden’.
De noordelijke populatie Oosterse Zwarte Roodstaart, die
op basis van roep het taxon betreft dat in Europa wordt ge-
zien, wordt op basis van een publicatie van Fedorenko (2018)
beschouwd als aparte ondersoort. Naast het uiterlijk bevestigt
ook een analyse van de contactroepen (Martinez & van der
Spek 2022) dat deze populatie gescheiden is van de zuidelij-
ke. De beschrijving van het holotype van phoenicuroides laat
echter zien dat de gekozen naam voor dit nieuw beschreven
taxon (murinus) een junior-synomiem is: de noordelijke po-
pulaties zouden nog steeds phoenicuroides moeten heten,
terwijl juist voor de zuidelijke populaties een nieuwe naam
nodig is. Het taxon ‘aterrimus’ van Westerse Zwarte Rood-
staart uit Portugal en de zuidelijke helft van Spanje wordt
doorgaans niet erkend en samengevoegd met gibraltariensis.
Geluidsanalyses tonen echter aan dat deze vogels een iets
lagere roep hebben. Dat kan, naast de subtiele kleedverschil-
len van mannetjes, aanleiding zijn om de status van aterrimus
te heroverwegen.
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