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BVnPC, 7 (97): 124-127 (2018)
124
A male of Turdus merula (Linnaeus, 1758) showing an interesting colour
aberration (Passeriformes: Turdidae)
Un macho de Turdus merula (Linnaeus, 1758) mostrando una interesante aberración de color
(Passeriformes: Turdidae)
Torsten van der Heyden
Member of the editorial board of BV news Publicaciones Científicas – Hamburg (Germany) –
tmvdh@web.de
ABSTRACT: Information –illustrated with photographs– on a male specimen of the Common or Eurasian
Blackbird Turdus merula (Linnaeus, 1758) showing a colour aberration is given. The specimen was observed
in Hamburg, Germany.
KEY WORDS: Turdus merula (Linnaeus, 1758), Turdidae, Passeriformes, colour aberration, leucism,
progressive greying.
RESUMEN: Se da información –ilustrada con fotografías– acerca de un espécimen macho del mirlo común
Turdus merula (Linnaeus, 1758) mostrando una aberración de color. El espécimen se observó en Hamburgo,
Alemania.
PALABRAS CLAVE: Turdus merula (Linnaeus, 1758), Turdidae, Passeriformes, aberración de color,
leucismo, encanecimiento progresivo.
Introduction
As VAN GROUW (2013) stated, the correct “naming of colour aberrations in birds still causes
widespread difficulty and confusion”. Falsely, some whitish aberrations are (still) classified as “partial
albinos” (OGILVIE, 2001) – although the affected specimens are not albinos. Furthermore, as explained by
VAN GROUW (2006, 2018), “partial albinism” is not even possible.
Van Grouw listed seven main types of colour aberrations based on genetic mutations. Leucism is
defined as the lack of melanins (eumelanin and phaeomelanin) caused by the heritable absence of pigment
cells. In contrast to albinos, leucistic birds have normally coloured eyes (VAN GROUW, 2006, 2013, 2018;
KONTER, 2014).
While in most birds eumelanin as well as phaeomelanin are present, in the Common or Eurasian
Blackbird Turdus merula (Linnaeus, 1758) the colour of the plumage of adult males is caused by eumelanin
only (VAN GROUW, 2013). Consequently, partial or total leucism in adult males of T. merula is a lack of
eumelanin.
Much more often, white feathers in Blackbirds are caused by other reasons such as –heritable or non-
heritable– progressive greying, defined as the progressive loss of pigment cells with age, illness or food
deficiency (VAN GROUW, 2013, 2018).
BVnPC, 7 (97): 124-127 (2018)
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VAN GROUW (2013, 2018) stated that –compared with progressive greying– a typical characteristic
of partial leucism is a “normally patchy and bilaterally symmetrical” white pattern.
Observation
On 25-V-2018, the author was able to observe and photograph an adult male of T. merula with a
remarkable colour aberration (VAN DER HEYDEN, 2018a). The specimen showed “rings” of white feathers
around both eyes and some white feathers on the upper part of its head. The observation took place in the
author’s backyard in Hamburg, Germany.
One day later, on 26-V-2018, the same specimen could be observed and photographed again at the
same location (Figs. 1 and 2).
Fig. 1: Turdus merula (Linnaeus, 1758), male with colour aberration, Hamburg, Germany, 26-V-2018, (VAN
DER HEYDEN, 2018b).
https://www.biodiversidadvirtual.org/aves/Turdus-merula-img94261.html
Discussion
The colour aberration shown by the observed specimen of T. merula could be either interpreted as
partial leucism or progressive greying. On the one hand, as can be seen in figure 2, the white “rings” around
both eyes of the observed specimen are patchy and bilaterally symmetrical, a distinctive characteristic of
partial leucism. On the other hand, progressive greying occurs more frequently than leucism.
As birds moult their feathers in a more or less symmetrical way, some forms of progressive greying
may look symmetrical, at least in the beginning. Furthermore, bilaterally symmetrical pattern in leucism
normally does not involve the feathers around the eyes (Hein van Grouw, personal comment).
BVnPC, 7 (97): 124-127 (2018)
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Thus, the colour aberration shown by the observed specimen is most likely a case of progressive
greying.
Fig. 2: Turdus merula (Linnaeus, 1758), male with colour aberration, Hamburg, Germany, 26-V-2018.
Acknowledgements
I would like to thank Hein van Grouw (Natural History Museum, Tring, Great Britain) for helpful
information. Furthermore, I would like to thank my colleague Emilio Herrero for reviewing this paper.
References
KONTER, A. (2014). Fehlfärbungen bei Vögeln – nicht nur Albinismus und Leuzismus bewirken weißes
Gefieder! Regulus Wissenschaftliche Berichte, 29: 59-68.
OGILVIE, M. (2001). Albinism, partial albinism and all the other -isms! Available from:
http://www.birdsofbritain.co.uk/features/mao-jun-01.asp.
[Accessed on 7-VI-2018].
VAN DER HEYDEN, T. (2018a). Eurasian Blackbird (Turdus merula). Photograph to be found on iNaturalist
[Online database]. Available from:
https://www.inaturalist.org/observations/12805059.
[Accessed on 7-VI-2018].
VAN DER HEYDEN, T. (2018b). Turdus merula. Photograph to be found on BiodiversidadVirtual.org [Online
database]. Available from:
https://www.biodiversidadvirtual.org/aves/Turdus-merula-img94261.html.
[Accessed on 7-VI-2018].
VAN GROUW, H. (2006). Not every white bird is an albino: sense and nonsense about colour aberrations in
birds. Dutch Birding, 28: 79-89.
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VAN GROUW, H. (2013). What colour is that bird? The causes and recognition of common colour aberrations
in birds. British Birds, 106: 17-29.
VAN GROUW, H. (2018). White feathers in black birds. British Birds, 111: 250-263.
