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What Is Your Diagnosis?
Author(s):
Source: Journal of Avian Medicine and Surgery, 25(1):57-60. 2011.
Published By: Association of Avian Veterinarians
DOI: 10.1647/2010-058.1
URL: http://www.bioone.org/doi/full/10.1647/2010-058.1
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Journal of Avian Medicine and Surgery 25(1):57–60, 2011
’ 2011 by the Association of Avian Veterinarians
What Is Your Diagnosis?
History
A nestling yellow-billed cuckoo (Coccyzus
americanus) of unknown sex was found at the
base of a tree, unable to fly, and subsequently was
presented to the Wildlife Hospital of Louisiana.
On presentation, the cuckoo was bright and
alert and weighed 13 g. The bird was in poor body
condition (body condition score, 2/5), had incomplete feather growth, and was estimated to be
approximately 10% dehydrated. Oral examination revealed an intense red coloring of the oral
mucosa, with white nodules on the dorsal surface
of the oropharynx and on the tongue (Fig 1). The
remainder of the physical examination revealed
no other abnormalities. The bird’s behavior was
considered typical, and it appeared to have a
normal appetite. Initial treatment consisted of
subcutaneous fluids (100 mL/kg per day) with
feeding every 2 hours of a diet composed of
moistened kitten dry food supplemented with
calcium carbonate (Fluker’s Calcium with Vitamin D3, Fluker’s, Port Allen, LA, USA) sprinkled
on the food.
A fresh wet mount from the oropharyngeal
nodules was performed. A cotton-tipped applica-
Figure 1. Young, yellow-billed cuckoo, showing whitish nodules in the oropharynx during a begging display.
tor moistened with warm saline solution was used
to sample the areas, after which the swab was
rolled onto a microscope slide. The slide preparation was negative for microorganisms on direct
microscopic examination.
Please evaluate the history, physical examination findings, diagnostic test results, and Figure 1.
Formulate a list of differential diagnoses and a treatment plan before proceeding.
57
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JOURNAL OF AVIAN MEDICINE AND SURGERY
Diagnosis
A closer examination of the oral cavity with
surgical magnification loupes revealed the white
markings to be symmetrical in placement and
size, with intact underlying mucosa. The areas in
question were composed of an arrangement of
white papillae. The bird appeared healthy and
was gaining weight daily. Another nestling
yellow-billed cuckoo was brought in the next
week, and it had the same oropharyngeal marking
pattern as the bird described above. After 5 weeks
of hand-rearing, the 2 cuckoos were released back
into the wild. The mouth markings were considered normal for the species.
Discussion
Cuckoos belong to the family Cuculidae within
the order Cuculiformes that also includes the
Musophagidae (turacos). The family comprises
136 species and is further divided into 6 subfamilies, namely the Cuculinae (Old World cuckoos),
Centropodinae (coucals), the Coccyzinae (American cuckoos), Neomorphinae (New World
ground cuckoos), Phaenicophaeinae (malkohas
and couas), and Crotophagidae (anis).1 Cuckoos
are altricial, and nestling and fledgling cuckoos
are identified based on their zygodactyl feet.2 The
Coccyzinae comprises 18 species of American
cuckoos.1 These cuckoos do not reproduce as a
brood-parasite like their Old World counterparts
but are nest builders. However, yellow-billed
cuckoos sometimes lay eggs in the nests of other
species.3 The young of several cuckoo species
(including all Coccyzinae) singularize themselves
by the presence of white papillate patches in the
oropharyngeal cavity (Fig 2).1,3–5 The nestlings of
yellow-billed cuckoos have white tomia and a red
mouth gape, with the presence of 5 small white
papillate patches on the palate, 4 large ones along
the caudal part of the choana, 2 on the tongue,
and 1 large patch on its dorsal surface (Fig 2).3,5
These conspicuous mouth markings should not
be mistaken for lesions, such as those seen with
oral trichomoniasis, candidiasis, bacterial stomatitis, viral infection (poxvirus, herpesvirus), oral
capillariasis or other nematodes, or squamous
metaplasia caused by vitamin A deficiency.6 Most
of these conditions can be diagnosed with a fresh
wet mount or a gram-stained surface cytologic
preparation. A fine-needle aspirate, biopsy, or
culture may be needed for a diagnosis in some
disease presentations (neoplasia, granulomas). If
the normal papillate patches are confused with
lesions, then unnecessary diagnostic tests and
treatments may be undertaken, with possible
iatrogenic adverse effects. Key characteristics of
the markings that suggest normality are symmetry
as well as the absence of signs of oropharyngeal
inflammation. A closer inspection with magnification or the availability of different individuals
of the same species can also help in differentiating
normal anatomic variation from pathologic
lesions. Endoscopic examination of the oral
cavity may also provide better details and higher
magnification for examination of the oropharynx.
In nestlings of altricial birds, the mouth gape is
usually brightly colored, and different marking
patterns, which disappear when the bird is
weaned, may be present, depending on the
species. Mouth markings are part of a complex
begging display, to stimulate a feeding response
and solicit care by the parents.7 Nestling mouth
color and markings enhance an adult’s ability to
detect nestlings, especially in dark nest sites.7
Mouth color can also signal hunger and quality
of the offspring (immune status, general state).7,8
The white papillae of some species of cuckoos
may improve their chance of being fed by acting
as visual cues for the parents.7,9 Brood-parasitic
species of cuckoos also have a complex begging
display with different features, including mouth
color adaptations, to mimic begging displays of
several host species.7,10 In general, brood-parasitic
cuckoo nestlings have no mouth marking, whereas species-specific patches are often present in the
mouth of nest-builder species.10
In avian medicine, a good knowledge of
morphologic and anatomic peculiarities is essential when working with zoological and unusual
avian species. The class Aves is the most diverse
among the terrestrial vertebrates, with a total
number of species close to 10 000.11 Although a
general body shape is usually conserved across
avian species, morphologic adaptations related to
various display behaviors are numerous in birds,
with some being temporary, such as during
courtship and begging periods.
This case was submitted by Hanna L. Cook,
College of Veterinary Medicine, Mississippi State
University, Starkville, MS 39762, USA, and
Hugues Beaufre`re, DrMedVet, Veterinary Clinical
Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803,
USA.
WHAT IS YOUR DIAGNOSIS?
59
Figure 2. Mouth patterns of young cuckoos: 1, black-billed cuckoo; 2, yellow-billed cuckoo; 3, great spotted
cuckoo; 4, guira cuckoo; 5, groove-billed anis; 6, red-capped coua; 7, pheasant coucal; 8, violaceous coucal; 9,
coquerel’s coua (Payne RB. The Cuckoos. Oxford University Press, Oxford, UK; 2005. Reprinted with permission of
Oxford University Press).
References
1. Payne RB. Family Cuculidae (cuckoos). In:
delHoyo J, Elliott A, Sargatal J, eds. Handbook
of the Birds of the World. Rockville Center, NY:
Lynx Edicions; 1997:508–610.
2. Purdin G. Chick identification. In: Gage LJ, Duerr
RS, eds. Hand-Rearing Birds. Ames, IA: Blackwell
Publishing; 2007:15–37.
3. Payne RB. Yellow-billed cuckoo. In: Payne RB,
ed. The Cuckoos. Oxford, UK: Oxford University
Press; 2005:339–345.
4. Duerr RS. General care. In: Gage LJ, Duerr RS,
eds. Hand-Rearing Birds. Ames, IA: Blackwell
Publishing; 2007:11.
5. Nolan V. External differences between newly
hatched cuckoos (Coccyzus americanus and C.
erythropthalmus). Condor. 1975;77(3):341.
6. Lumeij JT. Gastroenterology. In: Ritchie BW,
Harrison GJ, Harrison LR, eds. Avian Medicine:
Principles and Application. Lake Worth, FL:
Wingers Publishing; 1994:482–521.
7. Kilner RM. The evolution of complex begging
displays. In: Wright J, Leonard ML, eds. The
Evolution of Begging: Competition, Cooperation,
and Communication. Dordrecht, The Netherlands:
Kluwer Academic Publishers; 2002:87–106.
8. Saino N, Moller P. Immunity and begging. In:
Wright J, Leonard ML, eds. The Evolution of
Begging: Competition, Cooperation, and Communi-
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cation. Dordrecht, The Netherlands: Kluwer Academic Publishers; 2002:245–267.
9. Soler M, Martinez JG, Soler JJ, et al. Preferential
allocation of food by magpies Pica pica to great
spotted cuckoo Clamator glandarius chicks. Behav
Ecol Sociobiol. 1995;37(1):7–13.
10. Payne RB. Brood parasitism. In: Payne RB, ed.
The Cuckoos. Oxford, UK: Oxford University
Press; 2005:137–153.
11. Monroe BL, Sibley CG. A World Checklist of
Birds. New Haven, CT: Yale University Press;
1993.