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103
ORNITOLOGIA NEOTROPICAL 22: 103–110, 2011
© The Neotropical Ornithological Society
FIRST NESTING RECORDS OF THE ENDEMIC
SLENDER-BILLED PARAKEET (ENICOGNATHUS
LEPTORHYNCHUS) IN SOUTHERN CHILE
Maurice Peña-Foxon1, Silvina Ippi2, & Iván A. Díaz3
1Instituto de Ecología y Evolución, Facultad de Ciencias, Universidad Austral de Chile,
Casilla 567, Valdivia, Chile. E-mail: maurice.pena@gmail.com
2Instituto de Ecología y Biodiversidad, Departamento de Ciencias Ecológicas, Facultad de
Ciencias, Universidad de Chile, Las Palmeras 3425, Ñuñoa, Santiago, Chile.
3Instituto de Silvicultura, Facultad de Ciencias Forestales y Recursos Naturales, Universidad
Austral de Chile, Casilla 567, Valdivia, Chile.
Resumen. – Primeros registros de nidos de Choroy (Enicognathus leptorhynchus) en el sur de
Chile. – Documentamos los primeros antecedentes sobre la nidificación del loro Choroy (Enicognathus
leptorhynchus) obtenidos a partir de dos nidos naturales ubicados en el bosque templado del sur de
Chile. Los nidos se encontraron en cavidades naturales a 19 m de altura en árboles emergentes del
dosel. La postura alcanzó hasta 10 huevos y eclosionaron 4 y 5 pichones, respectivamente. El período
de incubación duró aproximadamente 30 días, y los polluelos permanecieron en el nido alrededor de
otros 40 días. Los pichones tuvieron una pérdida de peso previo a abandonar el nido y siguieron cre-
ciendo una vez fuera. Los pichones desarrollaron dos plumones distintos antes de la aparición de las
plumas, un patrón previamente descrito para un loro endémico de la alta cordillera de Colombia. Esto
podría ser una estrategia de los psitácidos habitantes de zonas frías para combatir las bajas temperatu-
ras mientras permanecen en el nido. Nuestro trabajo confirma la necesidad de seguir estudiando la
biología reproductiva de los psitácidos que habitan las zonas templadas, en particular de Sudamérica.
Abstract. – We report the first data on nesting ecology of the Slender-billed Parakeet (Enicognathus lep-
torhynchus) from two wild nests in native temperate rainforests of southern Chile. Nests were located in
natural cavities 19 m up in emergent trees. Posture reached up to ten eggs and clutched four and five
nestlings, respectively. Incubation period extended around 30 days, and nestling period around 40 days.
Nestlings presented mass recession before fledging and finished their development once out of the nest.
They exhibited two successive downs before feather emergence, a similar pattern shared with species
from high-elevated mountains in tropical Andes. This may be a strategy, for psittacines inhabiting cooler
regions, to overcome low temperatures while in the nest. Our study points out the necessity to collect
additional information on breeding biology in the wild for this and other southern temperate psittacines.
Accepted 12 February 2011.
Key words: Slender-billed Parakeet, Enicognathus leptorhynchus, Psittacidae, Nothofagus forest, tem-
perate rainforest, Chiloé Island.
INTRODUCTION
The ecology of psittacines inhabiting temper-
ate ecosystems is barely known compared to
species present in tropical and subtropical
ecosystems. Species living in temperate or
high-elevated ecosystems show differences in
nesting biology with other psittacines. For
104
PEÑA-FOXON ET AL.
instance, high-mountain living species, such
as the Thick-billed Parrot (Rhynchopsitta pachy-
rhyncha) from Mexico and the Azure-winged
Parrot (Hapalopsittaca fuertesi) from Colombia,
have respectively higher nest success and
lower growth rate than counterpart lowland
psittacines (Monterrubio et al. 2002, Tovar-
Martínez 2009). In Argentina, nestlings of the
Patagonian Burrowing Parrot (Cyanoliseus pat-
agonus) remain longer in the nest than other
psittacines of similar weight (Masello & Quill-
feldt 2002). The growth of two consecutive
downs during nestling’s stage in high-moun-
tain psittacines species has also been high-
lighted (Collar 1997, Tovar-Martínez 2009).
Despite these evidences, so far studies have
been insufficient among psittacines living in
cooler environment, e.g., concerning the
question if their nesting biology stands out
from tropical species. Even less data are avail-
able to indicate whether characteristics pre-
sented by high-mountain living psittacines
can be applied to species inhabiting temperate
latitudes.
The Slender-billed Parakeet (Enicognathus
leptorhynchus) is one of the two psittacids
inhabiting the temperate rainforests of south-
ern South America (Fjeldså & Krabbe 1990,
Juniper & Parr 2003). The species is endemic
to Chile and ranges from Santiago (33°S) to
Aisén (45°S). Its populations have declined
since the 1950’s due to habitat loss, shooting,
and disease (Fjeldså & Krabbe 1990, Juniper
& Parr 2003, Forshaw 2006) although it is not
currently considered globally endangered
(IUCN 2010). Little is known about the ecol-
ogy and reproductive biology of this parakeet,
particularly in respect to its nesting require-
ments and breeding success. Herein, we
describe aspects of the breeding biology of
the Slender-billed Parakeet from two natural
nests discovered in a temperate rain forest of
southern Chile. We expect that this study will
contribute to the better understanding of the
ecology of southern temperate psittacines.
METHODS
This study was conducted in the north-east of
the Chiloé Island (41°S, 73°W). The land-
scape is a mosaic of old-growth and second-
ary native forest fragments in an
anthropogenic matrix of agricultural fields
(Willson & Armesto 1996, Hoffmann et al.
1999, Willson et al. 2005). In the area, vegeta-
tion belongs to the North-Patagonian forest
type with a canopy dominated by Tepualia sti-
pularis, Drymis winterii, Podocarpus nubigena,
Nothofagus nitida, and several species of Myrta-
ceae. Emergent N. nitida trees over 20 m
height were sparsely distributed (Aravena et
al. 2002). The climate is temperate with a
mean annual temperature of 10.0 °C and a
mean annual rainfall over 2097 mm, falling
almost all year round (Carmona et al. 2010).
Nests were located in two forest frag-
ments > 100 ha, one in the Senda Darwin
Biological Station (SDBS) and the other in the
locality of Caulín, 6 km east of SDBS, both at
sea level. At each site we accessed a nest of
the Slender-billed Parakeet using tree climb-
ing techniques (Perry 1978, Dial & Tobin
1994). Nesting trees were characterized by
their height (using a 50 m tape) and diameter
at breast height (DBH). For each nest, we
measured its height from the forest floor,
horizontal and vertical diameter of entrance,
cavity depth from the base of the nest lip,
minimum internal diameter, and cavity orien-
tation (Saunders et al. 1982).
Nests were visited almost once a week
after their discovery and until the last nestling
left the nest. Egg size as well as bill, wing, and
tarsus length of each nestling were measured
to the nearest 0.1 mm using digital callipers
and at each nest inspection following
hatching (Moreno et al. 2005). For compara-
tive purposes, we obtained similar morpho-
metric data from 26 adult skins in the
Ornithology Collection of the National
Museum of Natural History of Chile. We
105
SLENDER-BILLED PARAKEET NESTING IN CHILE
limited the measurements taken depending on
the quality of individual museum skins sam-
pled. Body mass of nestlings was also
recorded using 1.0 g precision Pesola balances.
Morphometric data are given as mean ± one
standard deviation.
RESULTS
Nests were found in two large living N. nitida
emergent trees, both 23 m high. Nest tree
DBH was 82 cm and 98.5 cm in SDBS and
Caulín, respectively. Trees were similar in
shape; long and straight trunk without
branches until at 19 m, height where several
limbs constituted an emergent crown. Nest
cavities were located just below the crown at
19 m. Entrance holes were almost rounded
shape and measured 16 cm high by 12 cm
width for SDBS and 12 cm high by 9 cm
width for Caulín. Nest deeps from bottom of
entrance were 43 cm and 26 cm in SDBS and
Caulín nest respectively, and the narrowest
inner diameters were 20 cm for SDBS and 23
cm for Caulín. The nest cavity bottom was
garnished with finely chopped pieces of
wood. No other added materials were present,
with the exception of few sparse feathers
from the belly. Entrance orientation faced
southwest for SDBS and northeast for Caulín.
The SDBS nest was monitored 13 times.
The first visit (22 November 2006) took place
when only two eggs were present. By 21
December, the first hatchling was present
(Fig. 1), and by the last visit (14 February
2007) all fledglings had left the nest. On the
first visit to the Caulín nest (11 January 2007),
five nestlings were present. This nest was vis-
ited five times and by the last one (4 February)
the two last fledglings were still present at the
nest. Based on this information, the incuba-
tion period extended for 26–28 days and the
nestling period for 42–45 days.
The SDBS nest had up to 10 eggs, seven
of which were laid in a seven-day interval, rep-
resenting a rate of one egg per day. Mean
length and width of these 10 eggs plus one
unhatched egg from the Caulín nest were 35.0
± 1.7 mm and 26.4 ± 0.6 mm, respectively.
Four nestlings (40 %) hatched asynchronically
in the SDBS nest. Five of six eggs from the
SDBS nest that failed to hatch presented signs
of cracks or were destroyed. The shells of
hatched eggs were not removed by adults but
they disappeared with time. At hatching,
chicks had a white thin hair-like down which
was replaced progressively by a shorter,
denser, and grey down (Fig. 1) around day 10.
The Caulín nest was discovered containing
five nestlings with feathers already emerged
from wings and one unhatched egg, suggest-
ing a minimum clutch of six eggs. Pre-fledg-
ing data of bill and wing length and body mass
come from Caulín as last visits were realized
much closer to fledging day (4 days gap
between last and second last visit) than in
SDBS nest (9 days gap), giving a better
approximation of prefledging data.
Bill growth showed a linear increase (Fig.
2), reaching 26.4 ± 1.2 mm (N = 5) at fledg-
ing. Wing growth also showed a linear
increase in length during all the nestling
period, reaching 186.0 ± 7.2 mm (N = 5) at
fledging. Tarsus growth showed strong
increase during the first days until stabilizing
around day 25 in 27.0 ± 0.8 mm (N = 9, Fig.
2). Average bill length of adult skins from
museum collection was 33.8 ± 1.4 mm (N =
25) while wing length was 212.3 ± 6.2 mm (N
= 26) and tarsus length 26.3 ± 1.1 mm (N =
23).
The body mass of the SDBS nestlings
progressively increased to a mean of 298.2 ±
3.6 g around day 35, then decreased to 269.7
± 6.4 g (N = 3, Fig. 2) on the last visit. Thus
nestlings lost a minimum of 10 % (28.5 g in
SDBS) of their mass during the last 7 to 10
days in the nest. Weight previous to fledge
recorded by the last inspection in Caulín was
248.4 ± 5.3 g (N = 5).
106
PEÑA-FOXON ET AL.
DISCUSSION
This study provides the first records of nest
characteristics and breeding aspects for the
Chilean Slender-billed Parakeet in the wild.
Nest cavities and trees were very similar in
both cases: same tree species, similar tree
shape, nest at the same height, similar
entrance and depth. In addition, as both nests
were situated just below the tree crown, they
presented easy access and gave a large view
across the surrounding forest, since these
emergent trees were above the forest canopy.
The breeding period on Chiloé Island lasts
from November to mid-February and agrees
with data provided by Fjeldså & Krabbe
(1990). However, our results indicate that it is
considerably longer than previously reported
(Johnson 1967).
The Slender-billed Parakeet and the
Colombian high-mountain Azure-winged
Parrot hatchlings exhibit the same two suc-
cessive downs previous to the development
of feathers (Tovar-Martínez 2009). These
downs, in particular the second denser one,
are likely to be an adaptation of psittacine
chicks to the relatively low temperatures at
high altitudes (Collar 1997). Climatic rainy
and cold conditions on Chiloé Island at sea
level present similarities compared to 3000 m
high Andean forest of Colombia (Tovar-Mar-
tínez 2009). Thus the two consecutive downs
may be a strategy of psittacines living in cold
environments to have better thermal insula-
tion while in the nest.
The body-mass recession observed before
fledging has already been reported for some
others psittacines (Aramburú 1997, Masello &
FIG. 1. A twenty days nestling of Slender-billed Parakeet with a short grey and dense down. Lower left
insert shows a one day hatchling with a white thin hair-like down, both from the nest at Senda Darwin
Biological Station.
107
SLENDER-BILLED PARAKEET NESTING IN CHILE
Quillfeldt 2002, Renton 2002, Tovar-Martínez
2009). The weight at fledging (248 g for
Caulín) was close to the weight reported by
Forshaw (2006) for adults (240 g). In contrast,
bill and wing lengths did not reach their maxi-
mum size by the time birds left the nest. Bill
length of adult specimens was 22 % longer
than those of pre-fledging in the Caulín nest.
Similarly, pre-fledging wing length repre-
sented 88 % of the average wing length mea-
FIG. 2. Morphometric measures and body mass of the four nestlings in the nest at Senda Darwin Biologi-
cal Station during the breeding period.
108
PEÑA-FOXON ET AL.
sured in adult museums specimens. At
contrary, tarsus length was similar between
wild nestlings before fledging and museum
specimens. Thus, young birds continue their
development after leaving the nest.
The SDBS nest revealed an extraordinary
clutch size for the Slender-billed Parakeet,
outnumbering a previous report of three to
six eggs (Goodall et al. 1946). Based on the
allometric curve of Masello & Quillfeldt’s
study (2002), an adult parrot of 240 g, such as
the Slender-billed Parakeet (Forshaw 2006),
should have a clutch size of 3.5 eggs. A similar
clutch size of 10 eggs has only been reported
previously for the Green-rumped Parrotlet
(Forpus passerinus), a small psittacid of 30 g
(Beissinger & Waltman 1991). However, in
general tropical birds exhibit smaller clutch
sizes than counterparts of temperate latitudes
(Skutch 1953, Young 1994, Martin et al. 2000,
but see Yom-Tov et al. 1994), and as Masello
& Quillfeldt’s allometric curve is based on
many parrot species of tropical and subtropi-
cal latitudes it might explain our observation.
Nevertheless, the possibility of a second
female laying eggs in the same nest can not be
neglected as the laying average rate of one egg
per day for a 7-day period is uncommonly
high for the family Psittacidae (Collar 1997)
and also because two eggs presented severe
damages on their shelves. Even if nests were
not monitored during long-term session in
this study and so any evidence of a third bird
visiting the nest cavity is unproven, the phe-
nomenon of multiple females sharing the
same nest exists and has been reported for
another psittacine, the Horned Parakeet (Eu-
nymphicus cornutus, Theuerkauf et al. 2009). As
well, evidence of egg destruction and/or
infanticide due to conspecific intruders in
Green-rumped Parrotlet, Palm Cockatoo
(Probosciger aterrimus), Crimson Rosella (Platy-
cercus elegans), and Eclectus Parrot (Eclectus
roratus) nesting attempts have been observed
or suggested by authors (Beissinger & Walt-
man 1991, Waltman & Beissinger 1992, Krebs
1998, Heinsohn & Legge 2003, Juniper &
Parr 2003, Murphy et al. 2003) who mainly
attributed this behavior to the lack of nesting
sites. The island of Chiloé, especially the
north, has been highly deforested for agricul-
tural purposes (Carmona et al. 2009) and,
together with selective logging, this reduces
the number of available cavities for secondary
cavity nesting birds (Díaz et al. 2005, Corne-
lius et al. 2008) and thus might increase com-
petition among psittacines.
Much remains to be learned on the Slen-
der-billed Parakeet and other parrots of the
temperate Neotropics. Our results provide
information, albeit the small sample size, on
nesting phenology and nest site characteristics
and describe a clutch size extraordinarily large
for the size of this species (which must be
confirmed by further studies). Additional data
on the biology, ecology, and distributional
local movements of this parakeet are neces-
sary to plan and develop successful strategies
to enhance its conservation and also to com-
prehend better its relationship to man, as the
species is considered in some places as a pest
to crops (Juniper & Parr 2003). Future forest
management should consider the critical nest-
ing period to enhance the conservation not
only of the Slender-billed Parakeet but also of
the highly endemic and endangered avifauna
of this region (Stattersfield et al. 1998). Simi-
larly, selective logging recreating natural dis-
turbance regimes and keeping old and large
N. nitida trees (alive or dead) will provide
appropriate nesting sites for the numerous
cavity nesting community (Franklin & Arm-
esto 1996, Willson & Armesto 1996, Díaz et
al. 2005, Ojeda et al. 2007, Cornelius 2008).
As this study contributes to the knowledge on
Slender-billed Parakeet nesting biology but
arises new interrogations, we hope the infor-
mation reported herein will encourage addi-
tional studies to be done on temperate
Neotropical psittacines.
109
SLENDER-BILLED PARAKEET NESTING IN CHILE
ACKNOWLEDGMENTS
We are especially grateful to Juan Luis Celis
for his field support and friendship provided
during this study, and to Mary F. Willson for
the valuable comments done to the manu-
script and Juan J. Armesto for the develop-
ment of our field work. We thank also Marco
Mora for his assistance during fieldwork and
Juan Carlos Torres-Mura, bird curator from
the National Museum of Natural History
(Chile) to provide access to the avian collec-
tion. Comments of C. Cornelius, V. S. Ojeda,
and a third anonymous reviewer greatly
improved this manuscript. We thank to Fon-
decyt Grant 1050225, to Gary Machlis and
the generous support provided by The Canon
National Parks Science Scholars Program to
I.A. Díaz, and to CONICYT grant PDA-24.
SI acknowledges support from a CONICYT
scholarship. This is a contribution to the
Research Program of LTSER network at
Senda Darwin Biological Station, Ancud,
Chiloé.
REFERENCES
Aramburú, R. M. 1997. Descripción y desarrollo
del pichón de la cotorra Myiopsitta monachus
monachus (Aves: Psittacidae) en una población
silvestre de Argentina. Rev. Chil. Hist. Nat. 70:
53–58.
Aravena, J. C., M. R. Carmona, C. A. Pérez, & J. J.
Armesto. 2002. Changes in tree species rich-
ness, stand structure and soil properties in a
successional chronosequence in northern
Chiloe Island, Chile. Rev. Chil. Hist. Nat. 75:
339–360.
Beissinger, S. R., & J. R. Waltman.1991. Extraordi-
nary clutch size and hatching asynchrony of a
Neotropical parrot. Auk 108: 863–871.
Carmona, A., L. Nahuelhual, & C. Echeverría.
2009. Los sistemas prediales y su compor-
tamiento espacial en la Comuna de Ancud, sur
de Chile. Abstract book, XVI Reunión de la
Sociedad de Ecología de Chile, 8–10 Octubre,
Valdivia, Chile.
Carmona, M. R., J. C. Aravena, M. A. Bustamante-
Sánchez, J. L. Celis-Diez, A. Charrier, I. A.
Díaz, J. Díaz-Forestier, M. F. Díaz, A. Gaxiola,
A. G. Gutiérrez, C. Hernández-Pellicer, S. Ippi,
R. Jaña-Prado, P. Jara-Arancio, J. Jimenez, D.
Manuschevich, P. Necochea, M. Nuñez-Avila,
C. Papic, C. Pérez, F. Pérez, S. Reid, L. Rojas, B.
Salgado, C. Smith-Ramírez, A. Troncoso, R. A.
Vásquez, M. F. Willson, R. Rozzi, & J. J. Ar-
mesto. 2010. Estación biológica Senda Darwin:
Investigación ecológica de largo plazo en la
interfase ciencia-sociedad. Rev. Chil. Hist. Nat.
83: 113–142.
Cornelius, C. 2008. Spatial variation in nest-site
selection by a secondary cavity-nesting bird in a
human-altered landscape. Condor 110: 615–
626.
Cornelius, C., K. Cockle, N. Politi, I. Berkunsky, L.
Sandoval, V. Ojeda, L. Rivera, M. Hunter, & K.
Martin. 2008. Cavity-nesting birds in Neotropi-
cal forests: cavities as a potentially limiting
resource. Ornitol. Neotrop. 19: 253–268.
Collar, N. J. 1997. Family Psittacidae (Parrots). Pp.
280–479 in del Hoyo, J., A. Elliott, & J. Sargatal
(eds). Handbook of the birds of the world. Vol-
ume 4: Sandgrouse to cuckoos. Lynx Edicions,
Barcelona, Spain.
Dial, R., & S. C. Tobin. 1994. Description of
arborist methods for forest canopy access and
movement. Selbyana 15: 24–37.
Díaz, I.A., J. J. Armesto, S. Reid, K. E. Sieving, &
M. F. Willson. 2005. Linking forest structure
and composition: Avian diversity in succes-
sional forests of Chiloé Island, Chile. Biol.
Conserv. 123: 91–101.
Fjeldså, J., & N. Krabbe. 1990. Birds of the High
Andes. Zoological Museum, University of
Copenhagen & Apollo Books, Svendborg,
Denmark.
Forshaw, J. M. 2006. Parrots of the world: an identi-
fication guide. Princeton Univ. Press, Princeton,
New Jersey, USA.
Franklin, J. F., & J. J. Armesto. 1996. La retención
de elementos estructurales del bosque durante
la cosecha: una alternativa para el manejo de
bosques chilenos. Ambiente y Desarrollo 12:
69–79.
Goodall, J. D., A. W. Johnson, & R. A. Philippi.
1946. Las aves de Chile, su conocimiento y sus
110
PEÑA-FOXON ET AL.
costumbres. Platt Establecimientos Gráficos S.
A., Buenos Aires, Argentina.
Heinsohn, R., & S. Legge. 2003. Breeding biology
of the reverse-dichromatic, co-operative parrot
Eclectus roratus. J. Zool. (Lond.) 259: 197–208.
Hoffmann, A. E., J. J. Armesto, R. Rozzi, & I. A.
Díaz. 1999. El bosque chilote. Editorial Defen-
sores del Bosque Chileno, Santiago, Chile.
IUCN 2010. IUCN Red list of threatened species.
Version 2010.4. Downloaded on 29 November
2010 from www.iucnredlist.org.
Johnson, A. W. 1967. The birds of Chile and adja-
cent regions of Argentina, Bolivia and Peru.
Volume 2. Platt Establecimientos Gráficos S.
A., Buenos Aires, Argentina.
Juniper, T., & M. Parr. 2003. Parrots: a guide to
parrots of the world. Yale Univ. Press, New
Haven, Connecticut, USA.
Krebs, E. A. 1998. Breeding biology of Crimson
Rosellas (Platycercus elegans) on Black Mountain,
Australian Capital Territory. Aust. J. Zool. 46:
119–136.
Martin, T. E., P. R. Martin, C. R. Olson, B. J. Hein-
dinger, & J. J. Fontaine. 2000. Parental care and
clutch sizes in North and South American
birds. Science 287: 1482–1485.
Masello, J. F., & P. Quillfeldt. 2002. Chick growth
and breeding success of the Burrowing Parrot.
Condor 104: 574–586.
Monterrubio, T., E. Enkerlin-Hoeflich, & R. B.
Hamilton. 2002. Productivity and nesting suc-
cess of Thick-billed Parrots. Condor 104: 788–
794.
Moreno, J., S. Merino, R. A. Vásquez, & J. J. Ar-
mesto. 2005. Breeding biology of the Thorn-
tailed Rayadito (Furnariidae) in South-Temper-
ate rainforests of Chile. Condor 107: 69–77.
Murphy, S., S. Legge, & R. Heinsohn. 2003. The
breeding biology of Palm Cockatoos (Probosciger
aterrimus): a case of a slow life history. J. Zool.
(Lond.) 261: 327–339.
Ojeda, V. S., M. L. Suarez, & T. Kitzberger. 2007.
Crown dieback events as key processes creating
cavity for magellanic woodpeckers. Austral
Ecol. 32: 436–445.
Perry, D. R. 1978. A method of access into the
crowns of emergent and canopy trees. Biotro-
pica 10: 155–157.
Renton, K. 2002. Influence of environmental vari-
ability on the growth of Lilac-crowned Parrot
nestlings. Ibis 144: 331–339.
Saunders, D. A., G. T. Smith, & I. Rowley. 1982.
The availability and dimensions of tree hollows
that provide nest sites for Cockatoos (Psittaci-
formes) in western Australia. Aust. Wildl. Res.
9: 541–556.
Skutch, A. F. 1953. Life history of the Southern
House Wren. Condor 55: 121–149.
Stat t e r s f i e l d , A . J., M. J. Crosby, A . J. L o n g , & D. C.
Wege. 1998. Endemic bird areas of the world,
priorities for bird conservation. Birdlife Inter-
national, The Burlington Press, Cambridge,
UK.
Theuerkauf, J., S. Rouys, J-M. Mériot, R. Gula, & R.
Kuehn. 2009. Cooperative breeding, mate
guarding, and nest sharing in two parrot species
of New Caledonia. J. Ornithol. 150: 791–797.
Tovar-Martínez, A. E. 2009. Crecimiento y desa-
rrollo del plumaje en pichones de la Cotorra
Aliazul (Hapalopsittaca fuertesi) en la cordillera
central colombiana. Ornitol. Colombiana 8: 5–
18.
Waltman, J. R., & S. R. Beissinger. 1992. Breeding
behavior of the Green-rumped Parrotlet. Wil-
son Bull. 104: 65–84.
Willson, M. F., & J. J. Armesto. 1996. The natural
history of Chiloe, Chile: on Darwin’s trail. Rev.
Chil. Hist. Nat. 69: 149–161.
Willson, M. F., K. E. Sieving, & T. L. De Santo.
2005. Aves del bosque de Chiloé: diversidad,
amenazas y estrategias de conservación. Pp.
468–476 in Sm i t h-Ramírez, C., J. J. A r me st o,
and C. Valdovinos (eds). Historia, biodiver-
sidad y ecología de los bosques costeros de
Chile. Editorial Universitaria, Santiago, Chile.
Yom-Tov, Y., M. I. Christie, & G. J. Iglesias. 1994.
Clutch size in passerines of Southern South
America. Condor 96: 170–177.
Young, B. E. 1994. Geographic and seasonal pat-
terns of clutch-size variation in House Wrens.
Auk 111: 545–555.