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Julian P. Hume & Hein van Grouw 168 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
Colour aberrations in extinct and endangered birds
by Julian P. Hume & Hein van Grouw
Received 20 December 2013
S
rails, pigeons, parrots and passerines. Some island species that disappeared in the
early 19th century, e.g. Lord Howe Gallinule Porphyrio albus, Rodrigues Parakeet
Psiacula exsul and Mascarene Parrot Mascarinus mascarinus, are known from
only a few skins and illustrations, whereas the Huia Heteralocha acutirostris of
New Zealand is known from hundreds of specimens. Furthermore, two North
American species—Passenger Pigeon Ectopistes migratorius and Carolina Parakeet
Conuropsis carolinensis—which became extinct in the early 20th century, are also
represented by hundreds of specimens. Other supposedly extinct bird species are
enigmatic. Confusion exists concerning the unique specimens of Sharpe’s Rail
Gallirallus sharpei and Townsend’s Bunting Spiza townsendi, paintings of a parrot
from the West Indies and an aberrant white Huia, as well as aberrant specimens
Strigops habroptilus
concerning these birds and why they became extinct, or have become extremely
rare, but few data are available concerning colour aberrations in certain specimens;
the literature is also riddled with incorrect terminology. This paper addresses
this shortfall and describes the various colour aberrations in these extinct and
endangered birds and why they have occurred.
and macaws) and Passeriformes (passerines) are all widely distributed, occurring on every
Walters 2012), especially those genera endemic to oceanic islands. This is primarily due to
exotic species. Many of these extinct taxa are known from very few specimens, particularly
those that disappeared in the 19th century. These include Lord Howe Gallinule Porphyrio
albus (ex. c.1844), Rodrigues Parakeet Psiacula exsul (ex. c.1875) and Mascarene Parrot
Mascarinus mascarinus (ex. c
represented by just two known skins. In contrast, Huia Heteralocha acutirostris (ex. 1907)
of New Zealand is known from hundreds of specimens (Fuller 2000) and the Critically
Strigops habroptilus by >1,000; both were particularly sought after
Conuropsis
carolinensis (ex. 1918) and Passenger Pigeon Ectopistes migratorius (ex. 1914), of the
continental USA, are known from at least 720 skins (Luther 1996) and 1,532 skins (Hahn
(Rothschild 1907, Greenway 1958, 1967, Fuller 1987, 2000, Butcher 1992, Hume 2007, Hume
aberrations. The unique specimens of Sharpe’s Rail Gallirallus sharpei, obtained in 1865 and
of unknown provenance but considered an extinct species (Olson 1986), and Townsend’s
Bunting Spiza townsendi, collected once in 1834 and also considered extinct (Paynter 1970),
, illustrations of an enigmatic
Amazona parrot from the West Indies, and a white Huia are also described.
Julian P. Hume & Hein van Grouw 169 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
This paper addresses the probable reasons why these colour aberrations occurred, and
elucidates some of the erroneous misconceptions associated with these birds. In particular,
describe any avian taxon exhibiting partial white feathering (van Grouw 2006, 2012, 2013).
Rallidae
LORD HOWE GALLINULE (SWAMPHEN) Porphyrio albus (White, 1790)
Endemic to Lord Howe, a small, remote island between Australia and New Zealand in the
Tasman Sea, c.600 km east of Australia, P. albus was considered common when discovered
predators, becoming extinct between 1832 and 1844 (Hindwood 1940). The population was
derived from Purple Gallinule P. porphyrio
status. Two specimens, as well as several contemporary illustrations and subfossil remains,
skin has accurate provenance data.
First Fleet vessels, the Lady Penrhyn
1991). The drawing depicts one white and two pied gallinules, and Smyth described the
demonstrate that the species was variably coloured, with some completely white, others
white with blue speckling, some entirely blue. Phillip (1789) described the adult female
Figure 1. Watercolour of live Lord Howe Gallinules
Porphyrio albus showing the various stages of
progressive greying discussed in the text. Fig.
1a (left) shows a pair exhibiting the same colour
aberrations as the extant specimens; illustration by
George Raper c.1790 (from Hindwood 1940). Fig. 1b
(above) shows the three colour stages described by
White (1790); illustration by Thomas Watling c.1792
(from Fuller 2000).
Julian P. Hume & Hein van Grouw 170 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
Figure 2. Comparison of the two extant specimens of
Lord Howe Gallinules Porphyrio albus, both of which
Purple Gallinule P. porphyria: Fig. 2a (top) holotype
NMW 50761; Fig. 2b (above left) WML D3213; Fig.
2c (above right) artist’s impression of the Liverpool
specimen (Julian P. Hume); Fig. 2d (left) Eastern Purple
Gallinule P. p. melanotus BMNH 1887.5.2.66 dorsal and
ventral views (Hein van Grouw). Note that the holotype
is completely white.
b
a
d
c
Julian P. Hume & Hein van Grouw 171 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
as all white, but was informed that the male had some blue on the wings. White (1790),
followed by Latham (1824) and Gray (1862), stated that young were all black, turning bluish
grey, then pure white with maturity (Fig. 1b). White’s (1790) statement that juveniles were
strongly suggests that the species exhibited the aberration progressive greying, which can
onset of this condition, the bird gains an increasing number of white feathers with every
moult. In the early stages, they are usually spread randomly over the bird, but eventually
the entire plumage is white. Progressive greying may or may not be inheritable; some forms
are related to age, while in others the progressive loss of pigment cells is due to inheritable
disorders such as vitiligo (van Grouw 2013). Progressive greying is common in birds,
especially in the Corvidae, Passeridae and Turdidae (van Grouw 2012). The aberration
Howe Gallinule’s bill and legs retained normal coloration.
The widespread Australasian subspecies of Purple Gallinule, P. p. melanotus (Fig.
2d), still occurs on Lord Howe and some exhibit blue and white feathering (Mayr 1941,
Ripley 1977), but it appears that these birds had disappeared entirely by 1977. Mayr (1941)
considered the survival of blue individuals was due to them being less conspicuous,
after the original population of white birds had disappeared; however, Hindwood (1965)
thought that blue birds occasionally arrived from Australia and interbred with the resident
confusing taxonomic literature (Rowley 1875, Forbes 1901, Rothschild 1907, Mathews 1928),
resident on Lord Howe.
NMW (Naturhistorisches Museum Wien) 50.761, type (Fig. 2a). This specimen was
Fulica albus, Norfolk
Island’ (Pelzeln 1873) in error. It is considered the type, as White (1790) mentioned that the
bird on which his drawing was based was deposited in the Leverian collection (Pelzeln
1873). The skin, which was originally mounted, is in good condition, and the natural red
and thus were probably reddish in life. The specimen is all white, with no trace of yellowish
sheen or any purple feathering (contra Rothschild 1907: 144). The remiges and rectrices are
shorter than in the Liverpool specimen (Greenway 1967).
WML (Liverpool World Museum) D3213 (Fig. 2b–c). A mount, this specimen was
originally obtained by Sir Joseph Banks, but the collection date is unknown. It must have
went to the Bullock collection, was purchased at auction by Lord Stanley in 1819, then
c.1850
(Forbes 1901). It is generally in good condition, considering its age, but with extensive
and is more concentrated on the head, especially near the dorsal surface of the shield. There
lateral rectrices are purplish brown. The remiges and rectrices are soft, and the primaries
shorter than in P. porphyrio (Forbes 1901, Greenway 1967). The bill, shield, iris, legs and
Julian P. Hume & Hein van Grouw 172 Bull. B.O.C. 2014 134(3)
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feet were bright red or yellow in life (Philip 1789, White 1790), but the bill and feet in the
Liverpool skin have been painted red.
Rothschild (1907) correctly suggested that P. albus was not albinistic, but that the
population was in the evolutionary process of becoming pure white. Our analysis of
contra
two extant specimens is caused by a presumably inheritable form of progressive greying.
all white. The individuals that occurred on Lord Howe until 1977 exhibiting white and blue
coloration were probably a local population of P. p. melanotus, which also carried the gene
for progressive greying. They too are now extinct.
SHARPE’S RAIL Gallirallus sharpei
Several rails are known from unique skins or illustrations, and the enigmatic Sharpe’s Rail
Gallirallus sharpei
Gallirallus philippensis (Olson 1986), an extremely
Guinea, New Caledonia and New Zealand, as well as Australia and Indonesia (Ripley 1977,
of which are not threatened, but Macquarie Island Rail G. p. macquariensis became extinct
c.1870 due to the introduction of feral cats and Wekas G. australis
The type of G. sharpei was received at the Rijksmuseum van Natuurlijke Historie, Leiden
1893, Olson 1986). The original range is unknown, but H. Schlegel thought that the bird was
Pardirallus maculatus
error that initiated great confusion over its true provenance (R. B. Sharpe in
allocation (Olson 1986), described it as a distinct species from South America in honour
in Peters 1934)
placed the rail in Hypotaenidia and, as it was never recorded again, this prompted Peters to
suggest that it might be an extinct species. Hypotaenidia
Gallirallus (Olson 1986), and Olson concluded that Sharpe’s
Rail, which was similar in many aspects of size and morphology to volant G. philippensis,
should be placed there too.
On many occasions, unique bird skins have been ignored by modern ornithologists,
especially those collected on islands during the 18th and 19th centuries, which has
commonly resulted in their relegation to dubious status. Based on the available evidence,
coloration, it probably represented an extinct species, and speculated that the skin was
procured from Java, Sumatra or Borneo. Unusually among island rails, which are often
reduction in wing length (Olson 1986).
RMNH (Rijksmuseum van Natuurlijke Historie, Leiden) 87485 (Fig. 3). Sharpe’s Rail
remiges dull brown, strongly barred white; sides of head, chin, throat and neck grey; rest of
Julian P. Hume & Hein van Grouw 173 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
aberration does not cause a qualitative and / or quantitative loss of pigment.
In general the appearance of a melanistic bird is dark, predominantly blackish, but this
their usual boundaries (the rest of the plumage is often somewhat darker too); (2) all
pigment distribution is changed, but plumage is not necessarily darker.
feathers’, which means that melanism is not necessarily an increase of pigment, but may be
(van Grouw 2013).
The possibility that G. sharpei represents a colour aberration was not considered until
mtDNA revealed that the specimen can be referred to G. philippensis (Naturalis unpubl.
data). Therefore the unique specimen of Sharpe’s Rail is not an extinct species (van Grouw
Figure 3. Sharpe’s Rail Gallirallus sharpei RMNH 87485 (left) exhibiting category 3 melanism compared with
G. philippensis RMNH 185133 (right) (© Steven van der Mije / Naturalis)
Julian P. Hume & Hein van Grouw 174 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
Columbidae
PASSENGER PIGEON Ectopistes migratorius (Linnaeus, 1766)
Probably once the most abundant bird species on Earth, its extinction is one of the most
abundant could be exterminated so quickly. Its range was inextricably linked to the eastern
deciduous forests of North America and Canada, from the Great Plains east to the Atlantic,
north to southernmost Canada, and south to Virginia and northern Mississippi. In winter
Cuba (Schorger 1955, Gibbs et al. 2001). Early accounts describe the immense numbers
of individuals that congregated during the nesting season and especially on migration,
in the early 1800s, and coincided with an increase in deforestation and commercial
exploitation, particularly following the development of new railroads and telegraph
systems after the American Civil War. Wherever the pigeon concentrated in numbers, it
was subject to wanton slaughter; they were in huge demand for meat and the feather trade
(Butcher 1992). By the end of the century the species was almost extinct. The last recorded
wild specimen was shot on 24 March 1900 (Fuller 2000). A few were kept in private aviaries,
but they proved poor breeders; the last, a captive female called Martha, outlived the rest by
four years. She died on 1 September 1914 in Cincinnati Zoo (Shufeldt 1915).
Figure 4. Passenger Pigeon Ectopistes migratorius BMNH 1939.12.9.4071 exhibiting the brown aberration (left)
van Grouw / © Natural History Museum, Tring).
Julian P. Hume & Hein van Grouw 175 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
Passenger Pigeon is known from at least 1,532 skins and 16 skeletons (Hahn 1963).
It was a large dove with long wings and a long graduated tail, and adults were sexually
dichromatic. Males had the head bluish grey; display area at back of neck iridescent bronze,
primaries and secondaries darker greyish brown; secondaries edged white; throat and
and orbital ring greyish blue.
BMNH (Natural History Museum, Tring) 1939.12.9.4071 (Fig. 4). This aberrant
specimen, an adult female, has no provenance other than it formed part of the Rothschild
collection at Tring. Rothschild had a great interest in colour aberrations and this specimen is
tail where grey normally occurs; the primaries, lower breast and belly are white; the black
of eumelanin’ (van Grouw 2013). This mutation is the most common in wild birds, and
females occur in the wild, as females need only one gene to express the recessive brown
mutation. In contrast, to produce a brown male, a heterozygous father and brown mother
are essential; the likelihood of this occurring under natural conditions is extremely remote.
The bill and feet are usually slightly paler in brown (not discernible in this specimen), but
eye colour remains the same (van Grouw 2012). The result of this aberration is that the black
whereby old feathers can be much paler than fresh ones (van Grouw 2012, 2013). The
Psiacidae
RODRIGUES PARAKEET Psiacula exsul (Newton, 1872)
also observed other parrots (our translation from the original manuscript):
Necropsiacus rodericanus]
are larger than a pigeon and have a very long tail, the head big as well as the beak;
most are from the southern islets to the south of island where they eat a small black
seed that produces a small shrub whose leaves have the scent of lemon, and come to
Julian P. Hume & Hein van Grouw 176 Bull. B.O.C. 2014 134(3)
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♂ Psiacula exsul] is slightly smaller, and much more
♀ P. exsul] is small, all green
and the beak black.’
visiting the main island for water. The astronomer Pingré, who was on Rodrigues to observe
rare, Necropsiacus
described (Newton 1872). A second transit expedition to the island took place in 1874,
1879, Hume et al. 2014). The parakeet was by now extremely rare, and Slater remarked on
Palaeornis exsul. I saw one specimen of this bird as I was going from my camp to a
distant cavern: unfortunately I had not my gun with me or I could easily have shot it as
Figure 5. The two extant specimens of Rodrigues Parakeet Psiacula exsul exhibiting the parblue aberration.
Male UMZC18/Psi/67/h/I (right) lateral and dorsal views; holotype female UMZC18/Psi/67/h/I (left) lateral
and dorsal views (Julian P. Hume).
Julian P. Hume & Hein van Grouw 177 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
it came within thirty feet of me: I believed it to be a male at the time, and it is probably
the one procured since by Mr Caldwell; I never had time to hunt for it subsequently.
that he had seen two specimens at the N. end of the Island, but I had never time to visit
that region.
Assistant Colonial Secretary, William James Caldwell (1875), who arrived on Rodrigues
12 May 1875, saw several parakeets during his stay, but was unable to obtain a specimen
himself. However, he did receive a male from a local resident and ship’s pilot, William
1876); it was probably that seen by Slater. This was the last time the parakeet was recorded.
CUMZ (University Museum of Zoology, Cambridge) 18/Psi/67/h/I ♀ holotype (Fig.
overall dull greyish glaucous, darker above, with a blue or green sheen depending on the
blue, becoming greener on vent; black collar from nostrils to sides of head; bill black, iris
black with yellow ring, legs and feet greyish black. Originally preserved in alcohol, the
specimen was removed from solution when it was described (Newton 1872).
CUMZ (University Museum of Zoology, Cambridge) 18/Psi/67/h/I ♂
in being larger and in having the top of head clearer glaucous, less grey; black stripe
more distinct, extending upwards from nostrils to nape of neck and almost meeting there;
primaries with dull black patch on inner web near tip; central secondaries dusky black;
Newton 1876). The feathers exhibit more wear than the female, and thus are less well
preserved.
The unusual coloration of P. exsul has caused much debate, so it is important to establish
a general overview of parrot coloration. The predominant greens of most parrots are not
true colours as they are not formed by green pigments; instead, the green is produced by
in all birds, melanin, or more precisely, eumelanin, is one of the pigments that determines
colours in parrots. Eumelanin is normally black or dark brown, but depending on the way
the microscopic pigment granules are arranged (i.e. their density) in the feather cells, it
deeper cells of the feather barbs, together with their special structure, distort the light as it
passes through, making the feathers appear blue. Thus, blue is a structural colour and not
barb, and combined with the structural blue coloration, creates the bright shades of green
characteristic of most parrot species (Martin 2002).
probably the commonest mutation in parrots and is, for obvious reasons, called blue. In
mutation to appear, a bird must inherit a gene for the mutation, in this case blue, from both
parents. The coloration caused by blue mutations varies in shade, depending on the normal
colours (wild type) in the relevant species. For example, in Psiacula the blue coloration
will be evenly distributed and intense, as is the original green of these species. In contrast,
an uneven distribution and intensity of green can result in an uneven distribution of blue
Julian P. Hume & Hein van Grouw 178 Bull. B.O.C. 2014 134(3)
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described P. exsul
the angle of light. This suggests that the cause of the colour aberration was due to a parblue
mutation rather than true blue.
MASCARENE PARROT Mascarinus mascarinus (Linnaeus, 1771)
species disappeared before anything was recorded of its ecology. A few captive birds
arrived in Paris during the late 18th century, by which time it was probably already extinct
Greenway 1958, 1967, Fuller 1987, 2000, Forshaw 1989); however, this is extremely unlikely
and the species was almost certainly extinct by c.1800 (Hume 2007). The specimen described
by Hahn was not preserved, but two exist, the holotype in Paris (MNHN 211; Fig. 6a,c) and
Mascarene Parrot (Latham 1781), as the skin has some white feathering (Fig. 6c). Latham
Mascarinus], with the mask in front. The
but irregularly sprinkled with white feathers throughout; the tail, part white, part
brown, but not regular; some of the quills and tail feathers being wholly white, while
the opposites, which should have answered them, were white and brown: it is a
particular and beautiful lusus naturae.’
Both skins are now faded, and in the 1790s, the wings and tail of the Paris specimen
faded coloration of the specimens and early descriptions and illustrations, which depict
the bird with a purplish head, black mask, pale brown body with darker wings and tail,
and white bases to the lateral rectrices (see Hume 2007). However, birds described in life
et al. 1999], a black hood on the head, the beak very large and
feathers white at base; bare skin around eye region, bill, bare skin around upper bill and iris
of the original coloration is discernible in the two extant skins (Fig. 6); only the black mask
and red bill are clearly visible.
MNHN (Muséum National d’Histoire Naturelle, Paris) 211 (Fig. 6a). No details exist
as to this specimen’s provenance, but probably it was one of the live individuals that
resided in Paris in the late 1700s (Hume 2007). Overall coloration uniform pale brown, with
Julian P. Hume & Hein van Grouw 179 Bull. B.O.C. 2014 134(3)
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Figure 6. The two extant specimens of Mascarene Parrot Mascarinus mascarinus: Fig. 6a (top left) holotype
MNHN 211 (Julian P. Hume); Fig. 6b (top right) NMW 50.688, dorsal and lateral views (Julian P. Hume);
the Paris holotype (centre left and centre) is not discernible in the Vienna specimen, and the tail has been
reconstructed. The irregular white feathering in the Vienna skin is due to poor diet in captivity.
Julian P. Hume & Hein van Grouw 180 Bull. B.O.C. 2014 134(3)
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paler; head brown with black mask; tail dark brown with white bases to lateral feathers; bill
bright red; legs greyish brown.
NMW (Naturhistorisches Museum Wien) 50.688 (Fig. 6b). The Vienna specimen was
purchased from the sale of the Leverian collection in 1806 (Pelzeln 1873, Schifter 1994).
Nothing else is known about it. Overall uniform brown, greyer on the head and neck, with
individual white feathers on mantle, back, rump and underparts; primaries pure white (one
side has been clipped), secondaries white with dark brown tips; head brown with black
mask; tail has white and dark brown feathers; legs and feet reddish brown.
The pale brown coloration is clearly an artefact of fading due to light exposure, from
grey to brown (Hume 2007, van Grouw 2013), which has occurred in other ancient skins
that were predominantly grey or black in life, but are now brown, e.g. a Captain James Cook
Moho nobilis, and Townsend’s Bunting Spiza townsendi (pers. obs.,
white feathering on the body, with white primaries and asymmetrical white tail feathers,
alive in Paris during the 1770s (Hume 2007). The clipped primaries further suggest that it
was caged. The dietary requirements of parrots were doubtless poorly known in the 18th
century, and almost certainly inadequate for maintaining a healthy bird. This specimen of
Mascarinus
tyrosine from its food, which is necessary for normal melanin synthesis. In consequence,
present. However, vasa parrots Coracopsis sp. and Mascarene Parrot are the only species
Mascarinus are obscure and not satisfactorily resolved. Based on
Coracopsis nigraet al
et al
convergent evolution or supports a close relationship remain unclear.
CAROLINA PARAKEET Conuropsis carolinensis (Linnaeus, 1758)
Formerly present over much of the eastern USA, from Florida and southern Virginia
subspecies, Eastern Carolina Parakeet C. c. carolinensis and Western Carolina Parakeet C. c.
ludovicianus
when described in the late 1700s, but as early as 1831 the species was rapidly declining as
a result of persecution due to its habit of damaging fruiting crops. The birds disappeared
an increase in collecting for aviculture. By the end of the 19th century, Carolina Parakeet
low and mortality high. The last bird died in Cincinnati Zoo on 21 February 1918 (Hume
expired just four years earlier.
Carolina Parakeet is known from at least 720 skins and 16 skeletons (Hahn 1963, Luther
1996) and c
The nominate subspecies was generally green with a bluish tint, paler on the underparts;
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forehead, lores, bare skin around eye and upper cheeks orange; rest of head and upper
part of neck, bend of wing, carpal edge and thighs yellow; outer webs of primaries yellow
and being generally paler. As far as we are aware, there has not previously been any
description of colour aberrations in the species.
NMW (Naturhistorisches Museum Wien) 50.795 (Fig. 7a). Purchased from the
Leverian sale in 1806, it appears that it may have been a captive individual (data from label).
and back being replaced by brownish orange and the underparts with yellow, with more
also replaced by orange, but the bill, legs and feet are normal. A second captive specimen
(NHMW 50.682) exhibits similar coloration and was also purchased from the Leverian sale.
The aberrant coloration exhibited by these birds is caused by an increase and abnormal
(Martin 2002). In very rare cases, the increase of red pigment is due to inheritable factors
persistent reddish feathering, and lack of direct sunlight, presumably resulting in a lack
of vitamin D, may also be a contributory factor. Given that the Vienna specimen was in
GEORGE EDWARDS’ PARROT Amazona sp. (Fig. 8a)
produced a watercolour of an unknown parrot (see Fuller 2000: 209; Fig. 8a). The painting
Figure 7a (left). Carolina Parakeet Conuropsis carolinensis
Julian P. Hume & Hein van Grouw 182 Bull. B.O.C. 2014 134(3)
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parrot from Jamaica. Drawn from Nature
the size of life by G. Edwards, July 1764.’
On the back in Edwards’ own hand is a
more detailed description, repeated here
verbatim:
yellow, the colours of the upper sides
casting faintly through them. This bird was
lent to me by Dr. Alexander Russel and is
preserved in his collection. It was shot in
Jamaica and brought Dryed to England. The
people on Jamaica did not remember Ever
to have Seen one of this species of Parrots
before.
Geo. Edwards, July, 1764.
Some of the fethers have their tipps red and
Others have them yellow. The fethers on the
under sides, Back and rump have yellow
Figure 8a (top). Watercolour dated July 1764 by George Edwards of an Amazona parrot, probably A. collaria,
exhibiting the opaline aberration; the skin was taken on Jamaica and brought to England, but its whereabouts
are unknown (© Errol Fuller). Fig. 8b (below). The two extant Jamaican Amazona
Amazon A. collaria
Amazon A. agilis BMNH 1845.4.29.3, second from left dorsal, and second from right ventral views, alongside
a Cuban Amazon A. leucocephala BMNH1890.6.1.158, third from left dorsal, and far right ventral views (Hein
van Grouw / © Natural History Museum, Tring).
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Because of the uniqueness of this specimen and the fact that it is associated with one
of the West Indian Islands, where so many parrot species have become extinct (Rothschild
George Edwards’ parrot has been discussed as a possibly extinct species (Shuker 1999,
Fuller 2000). It bears a strong resemblance to an Amazona parrot, a widespread genus in
Furthermore, two extant AmazonaA. collaria,
with a mean 25.62 cm in total length (nA. agilis, mean 23.83
c.24.3
cm long (from top of head to tail tip), is intermediate between A. agilis and A. collaria, and
fractionally larger than A. agilis. However, wing length is shorter, while combined head and
bill length is much larger than either species; bill depth is intermediate between the two.
from the illustration must be viewed with great caution.
secondaries, and green uppertail with outer tail feathers red at base of inner webs. Edwards’
depiction has predominantly red coloration, but more importantly it shows the blue in the
Although not from Jamaica, if there is any doubt concerning the collection locality, Cuban
Amazon A. leucocephala (Fig. 8b) might also be considered as another strong candidate for
A. collaria.
TABLE 1
Measurements of Jamaican Amazona parrots compared with Edwards’ Parrot painting. All specimens held
deviation]. Edwards’ Parrot falls within low range of A. agilis in all measurements except head length and
bill depth, which are too large compared with other measurements, suggesting that the painting was not
accurately drawn to scale.
Species
Amazona collaria
Amazona agilis
Edwards’ Parrot
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Strigopidae
KAKAPO Strigops habroptilus Gray, 1845
Formerly occurred on North Island, South Island and Stewart Island, and prior to human
occupation of the islands had one of the widest distributions of any New Zealand bird
especially rats, mustelids, domestic cats and dogs (Sutherland 2002), rapidly eliminated
it from most areas, and the demand for museum skins in the late 19th century, when
thousands were collected (Butler 1989), reduced the species to a few remote localities. The
last report on North Island was in 1927, three males were recorded on South Island in 1987,
but have not been recorded since, and the last record on Stewart Island was in 1997, when
et al. 2006). Due to
individual variation. The bill is pearly grey with an ivory tip, iris dark brown, and legs and
CMNZ (Canterbury Museum, New Zealand) Av2059 (Fig. 9a). This specimen was
Bay in Preservation Inlet (Galbreath 1989). Walter Buller, the New Zealand ornithologist
and dealer, kept it alive on a diet of potatoes before it became part of his collection (Butler
was vivid canary yellow, fading to pale yellow on the cheeks and throat; the bill was white
it to be one of his most precious specimens.
The yellow coloration is almost certainly due to the mutation ino, which can be
. Among parrot
breeders, this mutation is known as lutino, because of the predominant yellow colour.
AM (Auckland War Memorial Museum) LB8526 (Fig. 9b). A second aberrant specimen,
a relaxed mount, was collected by G. Mueller, a surveyor and engineer, in Jackson Bay,
wings. This aberration vaguely resembles certain forms of recessive leucism in parrots
(Martin 2002), but the overall appearance strongly suggests opaline (see Edwards’ Parrot),
melanin only in the feather tips (especially on head and mantle), the absence of melanin
Julian P. Hume & Hein van Grouw 185 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
parrots (Martin 2002), and if our opaline
determination is correct, the AM specimen
is probably female.
BMNH (Natural History Museum,
Tring) 1853.6.9.1 (Fig. 9d). The reduction
of melanin resulting in yellow is not the
Figure 9. Three colour aberrations exhibited by
Strigops habroptilus: Fig. 9a (top left). Ino
aberration CMNZ Av2059, dorsal, lateral and ventral
Zealand); Fig. 9b (top right) opaline aberration AM
LB8526, dorsal, lateral and ventral views (© Jason
(centre left) originally unpublished painting of CMNZ
parblue aberration BMNH 1853.6.9.1 type of S. greyi,
dorsal, lateral and ventral views (© Natural History
in the collection of Errol Fuller (Julian P. Hume); Fig.
1927.12.18.1 (Hein van Grouw / © Natural History
Museum, Tring) .
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One notable specimen (BMNH 1853.6.9.1) is the holotype of S. greyii (Fig. 9d), which has
an intense blue hue to the upperparts and some on the underparts, and was originally
feathers are particularly worn, which strongly suggests that it was kept in captivity. In both
specimens, the upperparts exhibit the more extensive and stronger blue hue. Although the
Jones in li. 2013), so it is more likely that the Tring specimen was caught because it was an
unusual coloration and subsequently kept in captivity. We believe, therefore, that both of
Because this mutation can be extremely variable depending on the wild type, the
phenotype can exhibit blue coloration that is unevenly distributed. In the case of a parblue
Callaeidae
HUIA Heteralocha acutirostris (Gould, 1837)
being relatively short and slightly decurved, and the female’s much longer and heavily
for chiseling at hard substrates such as decaying wood to extract insect larvae, whereas
females used their long, thin bill for probing crevices (Buller 1873). The fossil record reveals
time Europeans arrived the species was largely restricted to the south of the island. Huia
1907 (Myers 1923) despite claims that it survived until at least the 1960s.
Huia is known from hundreds of skins (Fuller 2000); a unique egg and subfossil
remains are at the Museum of New Zealand, Wellington. General coloration was black with
feet black. The sexes were similar; the juvenile duller, with a brownish wash. A specimen
c
was told that the specimen was for sale, but when he inquired about it, the owner had
already sold the bird (Buller 1905); its whereabouts are now unknown.
and therefore the dark eye is not reliable; it is unlikely that the individual exhibited true
albinism. Albinism, from the Latin Albus
in feathers, eyes and skin’ (van Grouw 2013). The complete lack of melanin is due to
the hereditary absence of the enzyme tyrosinase in the pigment cells, as this enzyme is
Julian P. Hume & Hein van Grouw 187 Bull. B.O.C. 2014 134(3)
© 2014 The Authors; Journal compilation © 2014 British Ornithologists’ Club
Vevers 1960). In almost all cases, this results in a completely colourless bird, whereas the
red or pinkish hue present in the eyes and skin is caused by blood being visible through the
colourless tissue. Albinos rarely occur in the wild, although the mutation is not uncommon
in birds. Their scarcity is due to the absence of melanin in the eye, which makes them
poor depth of vision. Therefore, it is not primarily the white plumage that makes albinos
vulnerable in the wild, but their poor eyesight; most succumb to starvation and predation
eliminates albinism as a cause. It is more likely that progressive greying, leucism or ino
was involved. In progressive greying, the bird would have moulted several times before
becoming entirely white, but an aberrant pied Huia would surely have been a target
for collectors; it is unlikely that such a bird went unnoticed, especially as it survived to
adulthood. Leucism, which is a congenital and heritable absence of pigment cells from all
of the skin areas where they would normally provide the growing feather with pigment,
is very rare in wild birds (van Grouw 2012, 2013), and thus probably can be ruled out.
As ino is not uncommon in wild birds, and individuals can be all white, it is the most
likely explanation for the aberration. The fresh plumage of an ino may show some very
bird almost pure white. Furthermore, although the eyes of an ino are also reddish due to
survive comparatively well in the wild and the mutation is not uncommon, we believe that
Heteralocha acutirostris
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Although we cannot be absolutely certain about the colour aberration of this Huia
without a specimen, the fact that the illustrated bird is a female strongly supports the
Cardinalidae
TOWNSEND’S BUNTING Spiza townsendi (Audubon, 1834)
Chester County, Pennsylvania, and described the following year (Audubon 1834). There
has been much debate as to its status, it being variously considered an extinct species
(e.g. Paynter 1970, AOU 1983), a colour variant of Dickcissel S. americana (Parkes 1985) or
a hybrid female S. americana × male Blue Grosbeak Passerina caerulea (E. Coues in Sharpe
1888). The type (USNM 10282) is in poor condition, with the original coloration now barely
discernible; the specimen has foxed, producing an overall wash of pale brownish beige (Fig.
11b).
Audubon (1834; Fig. 11c) described the fresh plumage as having the upperparts, head,
streaked black on interscapular area; eyestripe, chin, throat, central line on underparts
back, wings darker, rusty patch on shoulder, and superciliary stripe and underparts yellow,
speckled. Juvenile females are duller and browner, and have black or brown speckling on
upper breast.
Parkes (1985) suggested that Townsend’s Bunting was a female colour variant of
Dickcissel that lacked normal carotenoid pigments, resulting in the complete absence of
yellow. Holt (2002–03) questioned this conclusion, as Townsend explicitly stated that the
comparison of adult males, females and juvenile Dickcissels with the unique skin and
original illustration of Townsend’s Bunting (Audubon 1834) suggests that the situation is
far more complex. For example, the lack of yellow due to diet or a single genetic change
(Martin 2002).
If Townsend’s Bunting was a female Dickcissel as suggested by Parkes (1985), the
diagnostic brown crown and cheeks should still be present. Townsend stated that it was
a male, so it should have exhibited the black throat patch, unless juvenile. Finally, Holt’s
(2002–03) suggestion that the specimen was a juvenile male is supported by the lack of a
full black throat patch, but juvenile males are brown above, not grey. In the Townsend’s
Bunting specimen, there is black speckling (eumelanin) concentrated on the sides of the
At this stage, we cannot determine if the specimen of Townsend’s Bunting is the result
of hybridisation, a colour aberration, or caused by some other genetic change. That it might
be an extinct species is highly unlikely, but it cannot be ruled out. No molecular work has
been undertaken on the skin, but mtDNA analysis may be the only way to resolve this
conundrum.
Julian P. Hume & Hein van Grouw 189 Bull. B.O.C. 2014 134(3)
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Figure 11. Townsend’s Bunting Spiza townsendi: Fig.
11a (top) holotype, USNM 10282, male (Julian P.
Hume); Fig. 11b (above left) illustration showing
the specimen today (above), and how it would
have looked when described by Audubon in 1834
(below) (Julian P. Hume); Fig. 11c (above right)
from Audubon (1834); Fig. 11d (left) Dickcissel
S. americana, from left to right in lateral view,
adult male BMNH 1899.2.1.4108, juvenile male
BMNH 1885.13.14.147, and adult female BMNH
1899.2.1.4126 (Hein van Grouw / © Natural History
Museum, Tring). The cause of this probable colour
aberration is unclear.
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Discussion
Colour aberrations are not uncommon in birds (van Grouw 2006, 2013), so it is
unsurprising that they occur in extinct and threatened species. However, few of these
extinct bird colour aberrations had been analysed, despite the specimens themselves
being apparently well known. The factors involved in producing unusual coloration can
be complex, and it appears that in some species discussed here, illness and poor diet in
captivity resulted in aberrant plumage. There may also be a bias in collecting from wild
populations, e.g. the parblue aberration of Psiacula exsul, white Porphyrio albus or parblue
and yellow specimens of Strigops habroptilus
of Passenger Pigeon, >700 skins of Carolina Parakeet, and hundreds of Huias having been
collected, we have only located single colour aberrations of Passenger Pigeon and Huia,
and two Carolina Parakeets, none previously described in the literature. During the 19th
century, the demand for unusual colour varieties of birds was extremely high and examples
TABLE 2
caused by physical factors and not by true genetic aberrations.
Colour aberration Cause Species exhibiting
mutation
Progressive
Greying Partial or total lack of melanins in
feathers due to progressive loss of
pigment cells in some or all of the
skin areas with age.
coloured feathers. Bill and feet
Lord Howe Gallinule
Porphyrio albus
Melanism Abnormal deposit of melanin in
skin and / or feathers.
distribution is changed, but
plumage is not necessarily darker.
Sharpe’s Rail Gallirallus
sharpei
Brown
due to incomplete synthesis
(oxidation) of eumelanin.
Black becomes brown. Passenger Pigeon
Ectopistes migratorius
Poor physical condition in
captivity.
spread through the plumage. Carolina Parakeet
Conuropsis carolinensis
diet, resulting in disturbed melanin
synthesis.
Random white feathering
Mascarene Parrot
Mascarinus mascarinus
Opaline(1) Reduced melanin distribution,
especially in the body plumage,
and an enhanced spread of
A predominant reddish coloration
with minimal dark (melanin)
plumage markings.
Edwards’ Parrot Amazona
cf. collaria
Opaline(2) Reduced melanin distribution,
especially in the body plumage. Predominant yellow coloration
with minimal dark (melanin)
plumage markings.
Strigops
habroptilus
Ino(1) Strong qualitative reduction of
melanin.
visible Strigops
habroptilus
Parblue(1) Coloration between green and blue. Strigops
habroptilus
Parblue(2) As above. Coloration between green and blue. Rodrigues Parakeet
Psiacula exsul
Ino(2) As above
that is rapidly bleached to white by
exposure to light. Paler bare parts,
reddish eyes.
Huia Heteralocha
acutirostris
Undetermined Lack of lipochrome pigments?
Hybridisation? Loss of yellow pigmentation Townsend’s Bunting Spiza
townsendi
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Buller was considered to be one of his most prized possessions.
In ornithology in general, colour aberrations are poorly understood, which has been
further exacerbated by incorrect terminology (van Grouw 2006, 2012, 2013). For example,
often applied to extinct birds too, e.g. the Vienna Mascarene Parrot. The inherent condition
the individual lacks the enzyme tyrosinase, or white feathering can be explained by other
factors, e.g. leucism, ino, progressive greying and poor diet (van Grouw 2006, 2012, 2013).
Studies of extant birds that exhibit unusual coloration can assist understanding of why
similar aberrations occurred in extinct species, and can sometimes provide new information
about the bird’s ecology or a specimen’s history. In these cases in particular, it is important
to understand the processes involved and to use correct terminology (Table 2). The aim of
this study is to highlight extinct or endangered bird species that exhibit colour aberrations
and we would welcome hearing from curators with additional specimens of interest. It is
probable that many more examples exist than those discussed here.
Acknowledgements
(Naturalis) photographed specimens, and Alison Harding (NHM) made accessible rare books in her care. We
for kind hospitality and access to collections; Ross Galbreath for providing information on the white Huia;
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