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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 123, No. 3. September 2011 
The Wilson Journal of Ornithology 123(3):632-635, 2011 
Triorchidism in a Hummingbird 
Christopher C. Witt 1 - 3 and Emil Bautista 2 
ABSTRACT.—We report a Great-billed Hermit 
(Phaethomis malaris) with three testes, a condition 
known as triorchidism. This is the first case to our 
knowledge of triorchidism in Neoavcs, the clade that 
contains ~95 % of avian species diversity. Triorchidism 
is inferred to be an exceptionally rare congenital 
abnormality in wild birds with developmental cause 
and evolutionary implications that are distinct from 
testicular asymmetry. Received 16 November 2010. 
Accepted 21 March 2Oil. 
Triorchidism is the condition of having three 
testes. This and other forms of polyorchidism are 
associated with superfecundity, ‘amorous propen¬ 
sities,’ and ‘generative faculties' in mythology 
(Gould and Pyle 1896). The true pathology is 
poorly known due to a paucity of cases and is 
dependent on the underlying developmental cause 
(Leung 1988). Several instances of triorchidism 
have been reported in Domestic Chickens (Gallus 
gallus) (Katiyar et al. 1986. Shrivastava et al. 
1988, Hocking 1992) and in a captive-bred line of 
Japanese Quail (Com mix japonica) (McFarland 
1965), but the phenomenon of polyorchidism is 
otherwise scarcely known from non-human ani¬ 
mals. 
Triorchidism is typically thought to comprise a 
congenital developmental abnormality and is 
associated with normal histology and functional 
spermatogenesis in the third testis in more than 
half of human cases (Ozok et al. 1992. Spranger et 
al. 2002, Savas et al. 2009). It is distinct from 
testicular asymmetry, which is widespread in 
birds and has been found to correlate with age 
(Graves 2004) or secondary sexual characteristics 
(Mpller 1994; but see Kimball et al. 1997). The 
phylogenetic distribution of triorchidism in verte- 
' Museum of Southwestern Riolugy and Department of 
Biology, University of New Mexico. Albuquerque. NM 
87131, USA. 
"Centro de Omitologfa y Biodivcr,sidad (CORBIDI). 
Urbanizacidn Huertos de San Antonio, Surco, Lima. Peru. 
Corresponding author; e-mail: cwitt@unm.edu 
brates is poorly known due to a scarcity of reports. 
We describe a case of triorchidism in the Greal- 
billed Hermit (Phaethomis malaris) from the 
humid lowland forests of northeastern Pent, and 
review previous reports of triorchidism in birds, 
METHODS 
Wc conducted a site inventory during June 
2007 in the Rio Chipaota Valley. Department of 
San Martin. Peru, while concurrently collecting 
comparative data on bird physiology (Merkord et 
al. 2009). This work included collection of 
voucher specimens with detailed ancillary data 
for deposit in the collections of Centro de 
Ornilologia y Biodiversidad (CORBIDI. Lima. 
Peru) and the Ltniversity of New Mexico. 
Museum of Southwestern Biology (MSB. Albu¬ 
querque, New Mexico, USA). We collected the 
following data for all specimens using standard 
methods: (!) body mass, (2) hemoglobin concen¬ 
tration (using Hemocue 201+ with correction Tor 
avian blood, following Simmons and Lill 2006), 
(3) hematocrit. (4) red blood cell concentration, 
(5) presence of hematozoa in a Giemsa-stained 
blood smear. (6) skull ossification. (7) presence 
and dimensions of the bursa of Fabricius. and (8) 
identity, condition, and dimensions of gonads. 
OBSERVATIONS 
We captured a specimen of Great-billed Hermit 
on 15 June 2007 that proved upon autopsy to have 
an anomalous third testis (Fig. 1). The left testis 
appeared to be divided into two similarly sized, 
spherical testes (left-most testis 2.87 mm diant. 
center testis 3.41 mm diam). connected to a single 
ductus deferens. The right testis was slight!) 
smaller in size (2.65 mm diam) and appeared to be 
displaced posteriorly by the two left testes, which 
together occupied a substantial portion of the 
abdominal cavity. We lacked the ability to do 
histological examination in our remote field 
camp, but we suspect that all three testes were 
functional because they were similar in size and 
