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Variation of black bib in Common Redstart as potential identification pitfall in hybrids

Authors:
  • Hintermann & Weber AG

Abstract

The extent and exact pattern of the black bib is one of the most important plumage features when trying to separate Eastern Black Redstart Phoenicurus ochruros phoenicuroides from a hybrid Black x Common Redstart P ochruros x phoenicurus. During the last years, I received several claims of hybrids for which identification was solely based on an unusual large black bib but lacking other plumage features pointing towards such an identification. Here, I quantify the variation in the extent of the black bib in Common Redstart. I compare the results of the analysis of these two samples with a third sample of 16 well documented mixed singers from Germany and Switzerland to shed light on the appearance of such individuals. The proportion of males with a large black bib-patch is quite high in both samples of nominate phoenicurus males. Such birds seem to be regular and I suppose that this is not caused by hybridisation only. Black bib variation was quite similar for mixed singers compared with the other two samples. As a consequence, such mixed singers should be considered pure Common Redstarts imitating Black Redstart song until new analyses may prove differently.
313
Variation of black bib in Common
Redstart as potential identification
pitfall in hybrids
The extent and exact pattern of the black bib is
one of the most important plumage features when
trying to separate Eastern Black Redstart Phoeni-
curus ochruros phoenicuroides from a hybrid
Black x Common Redstart Pochruros x phoeni-
curus (van der Spek & Martinez 2018, 2023).
During the last years, I received several claims of
hybrids for which identification was solely based
on an unusual large black bib but lacking other
plumage features pointing towards such an
identification. At least some observers based their
identification on van der Spek & Martinez (2018).
However, the focus of van der Spek & Martinez
(2018) was on the separation of Eastern Black
Redstart from hybrids, while the separation of
Common Redstart Pphoenicurus from hybrids
was not dealt with. Van der Spek & Martinez
(2018) did thus not discuss the variation in the
extent of the black bib in Common.
Here, I quantify the variation in the extent of the
black bib in Common Redstart. Note beforehand
that the extent of the black is sometimes dicult
to judge and strongly dependent on a bird’s pos-
ture. However, the extent of the black bib varies in
males Common (eg, Kleinschmidt 1908). In many,
the black is restricted to the chin and throat or
protrudes marginally onto the central breast at
most but in some males the black clearly goes fur-
ther down. I demonstrate this by analysing two
dierent samples of males of nominate Common
Pp phoenicurus. The first sample includes 26 in-
dividuals photographed in the field in Switzerland
during the breeding period. The other sample in-
cludes 58 male specimens held in the Natural
History Museum of Basel (hereafter NMBS), most-
ly birds from Switzerland but also including mi-
grants. I compare the results of the analysis of
these two samples with a third sample of 16 well
documented mixed singers from Germany and
Switzerland to shed light on the appearance of
such individuals (Martinez et al 2019).
In sample 1, 10 individuals (38%) had black re-
stricted to the chin and throat, while nine (35%)
had black extending very slightly further down.
Seven individuals (27%) had black clearly going
further down (table 1). All these seven sang and
called like typical Common Redstart and raised
young with females Common in habitats typical
for and regularly occupied by the species. Details
of wing morphology could be deduced from 13
photographed birds, revealing classic Common
features (emarginations restricted to p4-6 and
wing spacing ratio in p6-7:p5-6 below 1:1; prima-
ries numbered from outer to inner). Examples of
three such birds can be found in plate 390-392.
In sample 2, 14 birds (24%) had black restricted
to the chin and throat only, 28 (48%) had black
extending very slightly further down and 16 (28%)
had black clearly going further down. In 39 speci-
mens of the sample, the size of the black bib,
measured from bill base to its lower limit, was
[Dutch Birding 45: 313-317, 2023]
390 Common Redstart / Gekraagde Roodstaart Phoenicurus phoenicurus, male, Ettingen, Basel-Landschaft,
Switzerland, 4 June 2010 (Nicolas Martinez) 391 Common Redstart / Gekraagde Roodstaart Phoenicurus phoeni-
curus, male, Riehen, Basel-Stadt, Switzerland, 25 May 2011 (Nicolas Martinez) 392 Common Redstart / Gekraagde
Roodstaart Phoenicurus phoenicurus, male, Bättwil, Solothurn, Switzerland, 14 June 2006 (Nicolas Martinez). Three
individuals from north-western Switzerland showing large black bib. Note exact shape of black bib, with black
reaching down furthest in centre and leaving prominent orange breast side, whereas black bib is clearly broader in
many hybrids (cf van der Spek & Martinez 2018).
314
393 Common Redstarts / Gekraagde Roodstaarten Phoenicurus phoenicurus, males, Natural History Museum Basel
(NMBS), Switzerland, 18 November 2022 (Nicolas Martinez). Top: Solothurn, Solothurn, Switzerland, 27 April 1953
(NMBS 11243); centre: Hausen am Albis, Zürich, Switzerland, 15 May 1974 (NMBS 17786); bottom: Goldau,
Schwyz, Switzerland, 2 April 1972 (NMBS 16828). Individuals with black restricted to chin and throat, black going
slightly further down and black clearly extending onto upperbreast (from top to bottom). Lowest bird has slight
emargination on p6 (cf plate 395-396).
Variation of black bib in Common Redstart as potential identification pitfall in hybrids
30.3 ± 4.1 mm, with a minimum of 21 mm and a
maximum of 36 mm (only birds with stretched
neck measured). Plate 393 shows typical exam-
ples of the three categories, while plate 394 gives
an overview of the observed variation. None of
the 50 individuals in which wing condition al-
lowed measurement had a wing spacing ratio
clearly outside the range of Common Redstart
(0.5-1.2:1 compared with 0.41-1.17:1 as reported
for the species by Martinez et al 2019). There was
no relevant correlation between the extent of
black bib and wing spacing ratio (y = -0.0013x +
0.715, R2 = 0.0016).
All birds except one showed emarginations re-
stricted to p3-5. The outlying bird, a second calen-
dar-year male caught in Goldau, Switzerland, on
2 April 1972 (NMBS 16828), had also a very slight
emargination on p6 on both wings (plate 395).
This can (very) rarely occur in Common Redstart
(Svensson 1992, Demongin 2016, Shirihai &
Svens son 2018), so is probably in itself not a diag-
nostic pro-hybrid feature. However, note that
none out of 90 individuals measured by Ertan
(2002) showed this. It is worth mentioning that the
Goldau individual was one of the individuals with
the most extensive black bib at the upper level
(plate 393) but that no other features pointed to-
wards a hybrid origin. Its wing spacing ratio
equalled 0.85:1. It showed a prominent white
front and a pale grey back with a sharp delimita-
tion towards the black bib on the neck sides (plate
396). Analysis of large skin samples may show if
individuals with a slight emargination on p6 are
always on the upper level of black bib variation.
Detailed nuclear genetic analyses of such birds
may also be useful.
The sample with mixed singers contained four
individuals (25%) with black restricted to the chin
and throat only, six (37.5%) with black extending
very slightly further down and another six (37.5%)
with black clearly going further down. Details of
wing morphology could be seen on photographs
for three of the birds (of which two showed a large
black bib), showing classic Common Redstart fea-
tures (emarginations restricted to p4-6, wing spac-
ing ratio of p6-7: p5-6 below 1:1).
The proportion of males with a large black bib-
patch is quite high in both samples of nominate
phoenicurus males. Such birds seem to be regular
and I suppose that this is not caused by hybridisa-
tion only. Lacking any genetic analyses, I thus do
not see any reason to not consider such birds as
315
Variation of black bib in Common Redstart as potential identification pitfall in hybrids
TABLE 1 Variation in extent of black bib in three samples of males Common Redstart Phoenicurus phoenicurus males:
birds photographed in north-western Switzerland during breeding period (sample 1), specimens held in Natural
History Museum of Basel (NMBS), Switzerland (sample 2) and well-documented mixed singers from Germany and
Switzerland (sample 3)
black bib NW Switzerland NMBS mixed singers
(sample 1) (sample 2) (sample 3)
restricted to chin and throat 10 (38%) 14 (24%) 4 (25%)
extending very slightly further down 9 (35%) 28 (48%) 6 (37.5%)
on upperbreast
clearly going further down than throat and 7 (27%) 16 (28%) 6 (37.5%)
extending onto upperbreast
total 26 58 16
394 Common Redstarts / Gekraagde Roodstaarten Phoenicurus phoenicurus, males, Natural History Museum Basel
(NMBS), Switzerland, 15 December 2022 (Nicolas Martinez). From left to right: Rothenburg, Luzern, Switzerland,
10 June 1974 (NMBS 17785); Solothurn, Solothurn, Switzerland, 27 April 1953 (NMBS 11243); Rudersberg, Baden-
Württemberg, Germany, 28 April 1929 (NMBS 7767); Fribourg, Fribourg, Switzerland, 9 May 1939 (NMBS 9003);
Birsfelden, Basel-Landschaft, Switzerland, 26 April 1974 (NMBS 17783); Zürich canton, Switzerland, 11 April 1998
(NMBS 9049); Sempach, Luzern, Switzerland, 28 August 1939 (NMBS 11935); Basel, Basel-Stadt, Switzerland,
22 June 1943 (NMBS 9345). Note variation in black bib.
pure Common Redstarts and the extent of the
black bib as a natural variation within phoenicu-
rus.
Black bib variation was quite similar for mixed
singers compared with the other two samples. As
a consequence, such mixed singers should be
considered pure Common Redstarts imitating
Black Redstart song until new analyses may prove
dierently (for instance based on detailed genetic
data). Nevertheless, potential hybrids strongly re-
sembling Common do definitely occur (‘type 5’
birds in Martinez et al 2019). Identification of
such birds should therefore rely on a combination
of several features focusing on the extent but also
the exact shape of the black bib, white front, white
wing-patch (in adults) and back colour, and best
be confirmed by details of wing morphology.
316
395 Common Redstart / Gekraagde Roodstaart Phoenicurus phoenicurus, second calendar-year male (collected at
Goldau, Schwyz, Switzerland, 2 April 1972; NMBS 16828), Natural History Museum Basel, Switzerland,
18 November 2022 (Nicolas Martinez). Note prominent emarginations on p3-5 as well as slight emargination on p6
(arrows).
396 Common Redstart / Gekraagde Roodstaart Phoenicurus phoenicurus, second calendar-year male (collected at
Goldau, Schwyz, Switzerland, 2 April 1972; NMBS 16828), Natural History Museum Basel, Switzerland,
15 December 2022 (Nicolas Martinez)
Variation of black bib in Common Redstart as potential identification pitfall in hybrids
317
Acknowledgements
I would like to thank David Marques from the Natural
History Museum of Basel (NMBS) for access to their
collection and for valuable comments on an earlier draft
of the paper, as well as all observers that shared their
photographs of mixed singers or published them on the
internet: André Bossus, Dominic Bürgi, Peter Hess,
Clau dia Hirschenhuber, Hermann Knüwer, Ralph Mar-
tin, Mathias Ritschard, Martin Wettstein, Bahar Sezer
Widmer and Simon Zingg.
References
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ni curus: phylogeography, natural hybridization and
population dynamics. Marburg.
Kleinschmidt, B 1908. Erithacus Arboreus. Berajah 1-14.
Martinez, N, Nicolai, B & van der Spek, V 2019. Hybrid
Redstarts in Europe and North Africa. Br Birds 112:
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Shirihai, H & Svensson, L 2018. Handbook of Western
Palearctic birds 1 – Passerines: larks to Phylloscopus
warblers. London.
Svensson, L 1992. Identification guide to European pas-
serines. Fourth edition. Stockholm.
van der Spek, V & Martinez, N 2018. Identification and
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Nicolas Martinez, Rodersdorf, Switzerland (nicolas.martinez44@yahoo.de)
Plumage variation or intrasexual
dimorphism in Maghreb Wheatear
and possible hybridisation with
White-crowned Wheatear
On 20 March 2010, Martijn Bunskoek, Rob Felix
and Mark Zekhuis observed a strange wheatear
Oenanthe along Tagdilt track near Boumalne
Dadès, Drâa-Tafilalet, Morocco (plate 397). It
show ed mixed characters compared with species
regularly seen in this general area, mainly Desert
Odeserti, Red-rumped Omoesta, Black Oleucura,
White-crowned Oleucopyga and Maghreb
Wheat ear Ohalophila. The unidentified wheatear
was a striking black-and-white bird, with mainly
black head, throat, upperparts and wing, and
completely white underparts. The closed tail was
mostly black with (apparently) white outer tail
feathers. The crown was mottled grey-black and a
broad white supercilium was present in front of the
eye, reaching backwards to the hindneck and most
prominent above the eye. Presumably the same
bird was photographed by Christian Jensen in the
same area on 26 March 2010 (https://pbase.com/
cristianjensen/image/123215235). It was identified
as a presumed male Maghreb x White-crowned
Wheatear Ohalophila x leucopyga hybrid (van
den Berg & Haas 2010) but this identification
could not be proven. A similar looking dark-
capped male Maghreb, paired with a very dark
female, depicted in Shirihai & Svensson (2018)
was photographed in Morocco in April and indi-
cates that such birds occur more often. Based on
the same photographs, it also seems that Maghreb
may sport white along the entire outer edge of the
outermost tail feathers, creating an impression
similar to that in the photographs of the Moroccan
bird. On 28 March and 7 April 2010, a female
Maghreb was observed visiting a nesting hole at
the same site but no male Maghreb was nearby
and the female was regularly chased o by a male
White-crowned Wheatear, with strong interactions.
[Dutch Birding 45: 317-321, 2023]
397 Presumed Maghreb Wheatear / vermoedelijke Wes-
te lijke Rouwtapuit Oenanthe halophila, male, Tagdilt
track, Boumalne Dadès, Drâa-Tafilalet, Morocco,
20 March 2010 (Martijn Bunskoek). Either aberrant or
dark-morph Maghreb or possible Maghreb x White-
crowned Wheatear Ohalophila x leucopyga hybrid.
Variation of black bib in Common Redstart as potential identification pitfall in hybrids
... 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 P phoenicurus and hybrids here, which will be dealt with extensively in a separate paper (Martinez 2023). ...
Article
Full-text available
The identification headache of separating males Eastern Black Redstart Phoenicurus ochruros phoenicuroides/murinus from hybrid males (Western) Black x Common Redstart P!ochruros x phoenicurus 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 vocalisations of hybrids (Martinez et al 2019) and Black Redstart taxa (Martinez & van der Spek 2022). This paper summarises the current state of affairs 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 P o gibraltariensis with extended red or orange on the underparts.
Article
Tübingen, University, Thesis (doctoral), 2000. Includes bibliographical references (p. 157-168).
Identification guide to birds in the hand. The 301 species most frequently caught in Western Europe
  • L Demongin
Demongin, L 2016. Identification guide to birds in the hand. The 301 species most frequently caught in Western Europe. Beauregard-Vendon.
  • B Kleinschmidt
Kleinschmidt, B 1908. Erithacus Arboreus. Berajah 1-14.