Coloration anomaly of a male Collared Trogon (Trogon Collaris)

Abstract

Reportamos la observación de un macho adulto de Trogon collaris con vientre amarillo, similar al color del vientre de Trogon violaceus o Trogon melanocephalus. El pico era de color amarillo sucio y el anillo orbital era oscuro. Con base en publicaciones sobre coloración anormal en otras especies, asumimos que fueron alteraciones genéticas o de desarrollo del individuo las que causaron el color amarillo en lugar del rojo usual del plumaje ventral.

Full text

Acta Zoológica Mexicana (nueva serie)
Instituto de Ecología A.C.
azm@ecologia.edu.mx
ISSN (Versión impresa): 0065-1737
MÉXICO
2007
Knut Eisermann / Kevin Omland
COLORATION ANOMALY OF A MALE COLLARED TROGON (TROGON COLLARIS)
Acta Zoológica Mexicana (nueva serie), año/vol. 23, número 002
Instituto de Ecología A.C.
Xalapa, México
pp. 197-200
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
Universidad Autónoma del Estado de México
http://redalyc.uaemex.mx

197
Acta Zoológica Mexicana (n.s.) 23(2): 197-200 (2007)
Nota Científica
COLORATION ANOMALY OF A MALE COLLARED TROGON
(TROGON COLLARIS)
Resumen. Reportamos la observación de un macho adulto de Trogon collaris con vientre
amarillo, similar al color del vientre de Trogon violaceus o Trogon melanocephalus. El pico era
de color amarillo sucio y el anillo orbital era oscuro. Con base en publicaciones sobre coloración
anormal en otras especies, asumimos que fueron alteraciones genéticas o de desarrollo del
individuo las que causaron el color amarillo en lugar del rojo usual del plumaje ventral.
Collared Trogon (Trogon collaris) occurs in several disjunct areas from central
Mexico to the northern half of South America east of the Andes (AOU 1998. Check-list
of North American birds. 7th ed. AOU. Washington D.C.). At least eight subspecies are recognized
(Dickinson 2003. The Howard and Moore complete checklist of the birds of the world. 3rd ed. Princeton
Univ. Press), and T. c. puella is the only subspecies occurring in northern Mesoamerica.
In Guatemala, Collared Trogon is widely distributed in humid forests from sea level to
approx. 2500 m (Howell & Webb 1995. A guide to the birds of Mexico and northern Central
America. Oxford Univ. Press; Eisermann & Avendaño 2006. In: E. Cano (ed.) Biodiversidad de
Guatemala, Vol. 1. Univ. del Valle de Guatemala. Guatemala. 525-623).
Coloration anomalies in birds have been frequently described involving many species.
These anomalies can be caused by hybridization and alterations of mechanisms of bird
coloration (Hill & McGraw (eds.) 2006. Bird coloration. I. Mechanisms and measurements.
Harvard Univ. Press), including unusual lack of pigments (albinism), unusual dominance of
dark pigments (melanism), deposition of ingested pigments (e.g. Gross 1965. J. Field
Ornithol. 36:67-71; Gross 1965. J. Field Ornithol. 36:240-242; Hill 2002. A red bird in a brown bag:
the function and evolution of colorful plumage coloration in the House Finch. Oxford Univ. Press), and
other pigmentation modifications (McGraw et al. 2003. Condor 105:587-592).
Slight individual or geographical variations in the coloration of trogons have been
described, e.g. orange to red-orange belly in Orange-bellied Trogon (T. aurantiiventris;
Stiles & Skutch 1989. A guide to the birds of Costa Rica. Cornell Univ. Press) and different grade
of paleness in ventral red plumage among different subspecies of Elegant Trogon (T.
elegans; Webster 1984. Condor 86:204-207). Haverschmidt (1968. Auk 85:499) reported
Violaceous Trogons (T. violaceus) with some red feathers within the yellow-orange
plumage. We are not aware of descriptions of strong alterations in Collared Trogon.
Here we report a coloration anomaly in a male Collared Trogon which was seen near
Antigua Guatemala.
Non-standardized bird observations were made approx. 5 km southeast of Antigua
Guatemala at Montaña La Carmona (14°32’N 90°42’W), Guatemala, on 23 January

198
2005, 8:00-12:00 h (CST). We surveyed pine-oak woodland at an elevation of 1900-
2150 m. The forest was dominated by the following trees: oak (Quercus sp.), cypress
(Cupressus lusitanicus), pine (Pinus sp.), and American Hornbeam (Carpinus
caroliniana). Nomenclature of bird species follows AOU (1998. op. cit.).
At approx. 10:10 h our attention was drawn to a trogon, which we identified as Collared
Trogon (Trogon collaris) by its warning call. The bird was perched on a branch in the
forest understory approx. 3 m above ground. We saw the trogon at a distance of 30 m for
approx. 5 min. under favorable light conditions. Observation with 10x42 binoculars revealed
an obvious yellow belly. According to closer inspection with 40x spotting scope we can
describe the bird as follows: Feathers on back, head and chest were dark metallic green.
The face had a black mask. The eye was dark with a bare dark brown or black orbital
ring. The bill was sooty yellow. A white chest band separated the green chest from the
yellow belly. The yellow resembled the color of the belly of Violaceous Trogon (T.
violaceus) or Black-headed Trogon (T. melanocephalus). Primaries were black with
white edges. The undertail was barred black and white, by which we identified the bird as
an adult male based on plate 33 in Howell & Webb (1995. op. cit.). The uppertail was
green with black tip. The edge of the uppertail appeared barred black and white.
We identified the observed bird as Collared Trogon (Trogon collaris) based on
voice and coloration features. The yellow belly did not match previous descriptions of
this species. Table 1 gives an account of color descriptions of adult males in the range
of T. c. puella, published by several authors. All reviewed accounts include red as
color of the belly. KO examined 139 skins of Collared Trogon in the collection of the
Smithsonian NMNH; none of the specimens showed any hint of yellow. The Orange-
bellied Trogon (Trogon aurantiiventris) of Costa Rica and Panama (AOU 1998. op.
cit.) has been discussed to be probably a color morph of Collared Trogon (Salvin &
Godman 1888-1904. Biologia Centrali Americana. Aves, Vol. 2. Taylor & Francis, London; Wetmore
1968. The birds of the Republic of Panama, part 2. Smithsonian Misc. Coll. 150; Stiles & Skutch
1989. op. cit.). Ecology, voice, and all exterior features, except the orange belly, are
identical to the Collared Trogon (Stiles & Skutch 1989. op. cit.). Recent phylogenetic
data has proven very close relationship between both taxa (Moyle 2005. Biol. J. Linnean
Society 84:725-738). We are not aware of descriptions of yellow-bellied T. aurantiiventris.
Dark eyerings and sooty yellow bills appear to be an intraspecific variation of T.
collaris. Some authors described a similar eyering color, and descriptions of bill color
vary from greenish-yellow to orange (Table 1).
We can only suggest on probable reasons for the coloration anomaly of the ventral
plumage. While iridescent greens of head and back plumage of trogons are based on
structural coloration (Durrer & Villiger 1966. J. Ornithol. 107:1-26), red and yellow ventral
feathers are assumed to be colored by carotenoid pigments (Johnsgard 2000. Trogons

199
and quetzals of the world. Smithsonian Institution Press. Washington and London). Although some
parrots have similar colors that are not carotenoids (McGraw & Nogare 2004.
Comparative Biochemistry and Physiology, B 138:229-233), the spectrum from normal red Collared
Trogons examined in the Smithsonian NMNH (KO, unpublished data) suggested a
typical saturated red carotenoid as compared to orioles ( Hofmann et al. 2007. J. Avian
Biology 38:163-171.)
Publication Belly Bill Orbital ring
Gould (1845.
Proc. Zool. Soc. London
, Part 8:18-20) scarlet orange
-
Ridgway (1911.
Bull.U.S.NationalMuseum
50, part 5) pure deep geranium red yellow
-
Dickey & van Rossem (1938 .
FieldMus.Nat.Hist.,Zool.Ser.
23) -dullyellow
d
u
s
k
y
b
r
o
w
n
Skutch (1956.
Auk
73:354-366) bright red bright yellow
d
a
r
k
b
r
o
w
n
Smithe (1966.
The birds of Tikal.
Natural History Press, New
York) bright red yellow
o
b
s
c
u
r
e
-
b
r
o
w
n
i
s
h
Land (1970.
Birds of Guatemala
. Livingston, Wynnewood, PA) red greenish-yellow no
n
o
t
i
c
e
a
b
l
e
e
y
e
r
i
n
g
Ridgely & Gwynne (1989.
A guide to the birds of Pana ma with
Costa Rica, Nicaragua, and Honduras.
Princeton Univ. Press) red yellow in
c
o
n
s
p
i
c
u
o
u
s
b
r
o
w
n
Stiles & Skutch (198 9.
op. cit.
)redyellown
o
c
o
n
s
p
i
c
u
o
u
s
b
a
r
e
Howell & Webb (1995.
op. cit.
) red bright yellow
o
r
a
n
g
e
-
r
e
d
Johnsgard (2000.
op. cit.
) pure deep red yellow in
c
o
n
s
p
i
c
u
o
u
s
b
r
o
w
n
Jones (2003.
Birds of Belize.
Univ. of Texas Press ) red yellow
r
e
d
Table 1
Color of exterior parts of adult male Collared Trogons according to several authors.
Carotenoids cannot be synthesized by birds, they need to be ingested (Brush 1981.
In: Bauernfeind, J. C. (ed.) Carotenoids as colourants and vitamin A precursors. Academic Press,
London. 539-562). Food can therefore affect the coloration, which has been tested on
several species. Pink plumage flush in Elegant Tern (Sterna elegans), Franklin’s
Gull (Larus pipixcan), and Ring-billed Gull (Larus delawarensis) is caused by
carotenoids (Hudon & Brush 1990. Condor 92:798-801; McGraw & Hardy 2006. J. Field
Ornith. 77:29-33). The plumage in male House Finches (Carpodacus mexicanus) is
carotine-based and varies from pale yellow to bright red (Hill et al. 2002. Proc. Royal
Soc. London, B 269:1119-1124). Hill & Benkman (1995. Wilson Bull. 107:555-557) reported a
drastic change in coloration in Red Crossbills (Loxia curvirostra) in a feeding
experiment with huge quantities of carotenoids. Experimental manipulation of
carotenoid supply changed yellow plumage of American Goldfinches (Carduelis
tristis) to orange and the scarlet red plumage of Northern Cardinals (Cardinalis
cardinalis) to pale red (McGraw et al. 2001. Physiological and Biochemical Zoology 74:843-
852). This suggests that the yellow ventral plumage of the Collared Trogon can not be
caused uniquely by a lack of carotenoids in the food, but by genetic or developmental
changes (e.g. mutation, hormones, carotenoid deposition, carotenoid modification).
McGraw et al. (2003. op. cit.) reported a mutant yellow Northern Cardinal lacking
all of four primary red carotenoids; it had instead a yellow carotenoid.

200
A distinct character of the population of Collared Trogon at Montaña La Carmona is
unlikely, because a normally colored Collared Trogon has been seen previously there
(KE, pers. observ.). The Violaceous Trogon (T. violaceus) has been observed at the
lower parts of Montaña La Carmona at approx. 1700 m (KE, pers. observ.). To our
knowledge no hybrid between Collared and Violaceous Trogon has been reported. We
do not believe the observed bird was an F1 hybrid, because almost all exterior features
and the voice matched descriptions of Collared Trogon. Our observations of anomalous
breast coloration in Trogon collaris increase our understanding of plumage color variation
across birds, and specifically in this relatively unstudied tropical genus and species.
Acknowledgments.We thank the curators of the Smithsonian National Museum of Natural History
(NMNH), Washington, D.C., for access to the bird collection. Frode Jakobsen assisted KO with
spectral measurements at the Smithsonian. We appreciate critical comments on the manuscript
made by Christopher M. Hofmann, David Unger, and Claudia Avendaño. Christopher M. Hofmann
also provided some of the cited references. We appreciate comments by two anonymous reviewers.
Knut EISERMANN1 and Kevin OMLAND2
1Association PROEVAL RAXMU,
Bird Monitoring Program,
c/o P.O. Box 098 Periférico,
Guatemala City. GUATEMALA.
knut.eisermann@proeval-raxmu.org
2Department of Biological Sciences,
University of Maryland Baltimore County,
1000 Hilltop Circle, Baltimore, MD 21250. USA.
omland@umbc.edu