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Population densities of curassows, guans, and chachalacas (Cracidae): Effects of body size, habitat, season, and hunting


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Understanding the factors that determine population densities is critical for conserving viable populations of threatened species. Half of the 50 species in the family Cracidae have experienced population declines. We conducted a literature review to explore the relations of population densities of cracids with body size, habitat, season, and hunting. We compiled 103 density data points for 27 species in 37 localities from Mexico to Argentina. There was no correlation between body mass and density. The larger cracines tended to have lower densities than penelopines, but densities in both subfamilies spanned a similar range of values. Intraspecific and interspecific densities varied among sites over 2 orders of magnitude (1-100 birds km-2). Some cracids exhibited plasticity in habitat use, with variable densities among habitats. There is evidence that some species performed local movements related to seasonality in rainfall or resource availability, leading to aggregations around water sources during the dry season or around seasonally abundant food sources. Hunting had a negative effect on population densities, but in some cases low to moderate hunting did not cause a decrease in density in comparison to nonhunted sites. Despite having similar ecologies, densities of cracid species are very variable, and each population seems to respond idiosyncratically to local factors, which requires care if data are extrapolated across populations or species. Future studies that aim to characterize cracid populations for conservation purposes should take into account possible intraspecific density variations related to seasonality, local movements, and habitat heterogeneity.
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Volume 118, 2016, pp. 24–32
DOI: 10.1650/CONDOR-15-51.1
Population densities of curassows, guans, and chachalacas (Cracidae):
Effects of body size, habitat, season, and hunting
Gustavo H. Kattan,
* Marcia C. Mu ˜
and David W. Kikuchi
Departamento de Ciencias Naturales y Matema
´ticas, Pontificia Universidad Javeriana Seccional Cali, Cali, Colombia
Biodiversity and Climate Research Centre (BiK-F) and Senckenberg Gesellschaft f¨
ur Naturforschung, Frankfurt am Main, Germany
Department of Biology, Carleton University, Ottawa, Ontario, Canada
* Corresponding author:
Submitted March 31, 2015; Accepted September 8, 2015; Published November 11, 2015
Understanding the factors that determine population densities is critical for conserving viable populations of
threatened species. Half of the 50 species in the family Cracidae have experienced population declines. We conducted
a literature review to explore the relations of population densities of cracids with body size, habitat, season, and
hunting. We compiled 103 density data points for 27 species in 37 localities from Mexico to Argentina. There was no
correlation between body mass and density. The larger cracines tended to have lower densities than penelopines, but
densities in both subfamilies spanned a similar range of values. Intraspecific and interspecific densities varied among
sites over 2 orders of magnitude (1–100 birds km
). Some cracids exhibited plasticity in habitat use, with variable
densities among habitats. There is evidence that some species performed local movements related to seasonality in
rainfall or resource availability, leading to aggregations around water sources during the dry season or around
seasonally abundant food sources. Hunting had a negative effect on population densities, but in some cases low to
moderate hunting did not cause a decrease in density in comparison to nonhunted sites. Despite having similar
ecologies, densities of cracid species are very variable, and each population seems to respond idiosyncratically to local
factors, which requires care if data are extrapolated across populations or species. Future studies that aim to
characterize cracid populations for conservation purposes should take into account possible intraspecific density
variations related to seasonality, local movements, and habitat heterogeneity.
Keywords: Cracidae, habitat use, hunting, population density, seasonality
Densidades poblacionales de paujiles, pavas y guach aracas: Efectos del tama ˜
no corporal, el ha
´bitat, la
estacionalidad y la cacer´
El estudio de los factores que determinan las densidades poblacionales, es cr´
ıtico para la conservaci ´
on de especies
amenazadas. La mitad de las 50 especies de la familia Cracidae esta
´n amenazadas. Hicimos una revisi ´
on de literatura
para evaluar las relaciones entre las densidades poblacionales de Cracidae y el tama ˜
no corporal, el ha
´bitat, la
estacionalidad y la cacer´
ıa. Obtuvimos 103 datos de densidades para 27 especies en 37 localidades entre M´
exico y
Argentina. No encontramos correlaci ´
on entre masa corporal y densidad. Las especies de Cracinae, que son ma
grandes, tienden a tener densidades ma
´s bajas que Penelopinae, pero en ambas subfamilias las densidades abarcan un
intervalo similar de valores. Las densidades intra e interespec´
ıficas var´
ıan geogra
´ficamente en dos ´
ordenes de
magnitud (1 a 100 individuos km
). Algunas especies tienen plasticidad en el uso de ha
´bitat y sus densidades var´
entre ha
´bitats. Hay evidencia de que algunas especies hacen movimientos locales relacionados con la estacionalidad
en la precipitaci ´
on o disponibilidad de recursos; los individuos se agregan alrededor de fuentes de agua durante la
estaci ´
on seca o alrededor de fuentes abundantes de alimento. La cacer´
ıa tiene un efecto negativo sobre las densidades
poblacionales, pero en algunos casos la cacer´
ıa baja a moderada no causa una disminuci ´
on en las densidades, en
comparaci ´
on con sitios sin cacer´
ıa. A pesar de tener ha
´bitos similares, las densidades de las especies de Cracidae son
muy variables y cada poblaci ´
on parece responder de manera idiosincra
´tica a los factores locales. Se requiere
precauci ´
on si se van a extrapolar datos entre poblaciones o especies. Los estudios futuros que busquen caracterizar las
poblaciones de Cracidae con prop ´
ositos de conservaci ´
on, deben tener en cuenta las posibles variaciones relacionadas
con estacionalidad, movimientos locales y heterogeneidad de ha
Palabras clave: Cracidae, uso de ha
´bitat, la caza, la densidad de poblaci ´
on, la estacionalidad
Q2016 Cooper Ornithological Society. ISSN 0004-8038, electronic ISSN 1938-5129
Direct all requests to reproduce journal content to the Central Ornithology Publication Office at
Cracidae is a family of galliform birds endemic to the
Neotropics (del Hoyo et al. 1994). The family contains 50
species, with their center of diversity in Colombia and
Ecuador. Cracids are classified into 2 subfamilies. The
Cracinae (curassows: 14 species) are large, mostly terres-
trial birds, whereas the Penelopinae (guans and chacha-
lacas: 36 species) are smaller and arboreal. Cracids are
largely frugivorous but have broad diets that include
animal matter and other foods (Mu ˜
noz and Kattan 2007).
This is one of the most threatened families of birds, with
24 species listed in the Threatened, Endangered, or
Critically Endangered categories (Brooks 2006). The major
causes of population declines in these birds are habitat loss
and hunting.
Developing spatially explicit conservation plans and
preserving viable populations of cracids requires under-
standing their patterns of distribution and abundance and
the processes that influence those patterns. Density is an
important parameter that influences population dynamics
through density-dependent vital rates. For example, at low
densities, reproductive rates may be reduced as a result of
Allee effects (inverse density dependence of per capita
growth rate at low densities; Courchamp et al. 1999). Local
population densities have been extrapolated to estimate
abundance in a larger area or across the geographic range
of a species, as a basis to estimate threat status (Renjifo et
al. 2014). However, this requires caution because of spatial
heterogeneity in density related to habitat structure and
other local factors (Hansen et al. 1995). If local densities
are highly variable, abundance estimates will be unreliable.
Many factors may influence population density and the
spatial dispersion of individuals. Two of the main factors
are body size and trophic level. There is a general negative
correlation between body size and population density
(Gaston and Blackburn 2000). However, most of the
variation in bird population density that is explained by
body size and trophic level occurs at the family and order
taxonomic hierarchies, which suggests that these traits are
phylogenetically conserved (McGill 2008).
Animal species normally exhibit large variations in
abundance of populations across their ranges, with small
numbers in most localities and a few abundance hotspots
(Brown et al. 1995, Lundberg et al. 2000). One half of the
variance in bird abundance (controlling for other factors,
such as taxonomic affiliation and trophic level) is due to
spatial variation within species (McGill 2008). Part of this
variation is related to a spatial cline of abundance from the
center to the periphery of the geographic range, which may
result from source–sink dynamics (Curnutt et al. 1996).
However, the generality of this clinal pattern has been
challenged, because densities show much more complex
spatial patterns (Sagarin et al. 2006). At local scales,
population densities may vary according to habitat
suitability in heterogeneous landscapes, which, in turn,
may be related to habitat structure or distribution and
abundance of resources (Boyce and McDonald 1999).
Density, however, is not a reliable indicator of habitat
suitability, because numerous ecological factors may lead
birds to settle in poor habitats (Johnson 2007).
Animals may also move in a landscape in response to
temporal changes in resource distribution and abundance
in different habitats, which may be related to seasonal or
aseasonal fluctuations in climate. For example, variations
in the availability of food resources are correlated with the
local abundance of forest birds (Levey 1988, Poulin et al.
1992), and locally abundant resources may lead to
temporary aggregations of individuals (Mu ˜
noz et al.
2007). In tropical mountains, birds may perform seasonal
elevational movements in response to variations in food
availability or climate (Boyle 2010, 2011).
Here, we use a literature review to explore how
population density of cracids is related to body size,
habitat heterogeneity within a locality, season, and
hunting. We expected cracines to exhibit lower population
densities than penelopines because of their larger sizes. In
particular, chachalacas (Ortalis spp.) comprise a group of
small penelopines that tolerate disturbed habitats (del
Hoyo et al. 1994), so we expected them to be the most
abundant. Curassows are considered sensitive to habitat
disturbance and hunting (del Hoyo et al. 1994), and we
expected these birds to be sedentary and restricted to
mature forest. We also expected population densities of
cracids to vary in relation to seasonality in rainfall and
resource availability. Finally, cracids should be strongly
affected by hunting.
We searched the scientific literature to build a database on
population densities of cracids. We used the keywords
‘‘cracid’’ and ‘‘bird population density’’ to find references in
Google Scholar, and looked for citations of these papers as
well as papers that they cited. We found 32 studies that
reported a total of 103 density data points. Studies
encompassed 27 species (10 Cracinae, 17 Penelopinae)
and 37 localities distributed from Mexico to Argentina
(Table 1).
The 32 studies used 4 main methods to estimate density.
Sixteen studies used distance sampling. Birds were
detected along transects, and the perpendicular distance
to the transect was estimated. Then, using the program
Distance (Thomas et al. 2009), data were used to generate
detection probability as a function of distance to the
transect and then to estimate density. In strip transects (10
studies), a detection distance determined by the observer
was used to define the area of the sampled strip (width 3
The Condor: Ornithological Applications 118:24–32, Q2016 Cooper Ornithological Society
G. H. Kattan, M. C. Mu ˜
noz, and D. W. Kikuchi Cracid population densities 25
length), and density was calculated as the number of
individuals detected divided by that area. Point counts
were used in 2 studies. A stationary observer detected
birds within a circle and used the maximum detection
distance to calculate the area sampled. Finally, 3 studies
estimated densities by spot mapping birds within a defined
study area.
We analyzed the effect of survey method (distance
sampling, strip transect, point counts, and spot mapping)
on the natural logarithm of population densities by using a
linear mixed model, which included species as a random
effect to account for potential taxonomic differences in the
methods used. We performed our analyses in R version 3.2
(R Development Core Team 2014). We did not find any
significant differences between densities estimated by the
various sampling methods (likelihood ratio test [LRT]; v2¼
1.18, df ¼3, P¼0.75), although our power to detect an
effect of the latter 2 methods was low because of the small
number of cases. In subsequent analyses we ignored survey
To calculate correlations between body mass and
population density, we used only data obtained in the
birds’ main habitat type (i.e. undisturbed, nonfragmented
forest) and in the absence of hunting. This gave us 24
species for analysis. Often, several density values were
available for each species in 1 or more localities. Therefore,
in conducting a linear regression of ln(density) against
ln(mass), we included species as a random effect in the
model. We also used regression analysis with species as a
random effect, to test for differences between cracine and
penelopine densities.
Four studies reported density data of 6 species in
different habitats within a locality. The study designs,
localities, and habitats were very heterogeneous, which
precluded a quantitative analysis of how densities varied
with habitat. Therefore, we present those results in a
descriptive form.
To analyze the effect of hunting on population density,
we first used studies in which hunted and nonhunted
forests were paired together at the same site. Three
TABLE 1. Species in the family Cracidae for which population densities have been reported and countries where they were studied.
Species Country References
Subfamily Cracinae
Crax Alberti Colombia Rodr´
ıguez 2008
C. alector French Guiana Thiollay 1989, 1994
C. daubentoni Venezuela Silva and Strahl 1997, Strahl et al. 1997, Bertsch and Barreto 2008
C. fasciolata Brazil Desbiez and S˜
ao Bernardo 2011
C. globulosa Colombia, Brazil, Bolivia, Peru Alarc ´
on-Nieto and Palacios 2008, Haugaasen and Peres 2008,
Hill et al. 2008, Yahuarcani et al. 2009
C. mitu Peru Terborgh et al. 1990
C. rubra Guatemala, Mexico Mart´
ınez-Morales 1999, Eisermann 2004
Mitu tuberosa Peru, Brazil, Bolivia Torres 1997, Begazo and Bodmer 1998,
Haugaasen and Peres 2008, Hill et al. 2008, Barrio 2011
Nothocrax urumutum Peru Parker 2002
Pauxi pauxi Colombia, Venezuela Silva and Strahl 1997, Setina et al. 2012
Subfamily Penelopinae
Aburria aburri Colombia, Venezuela Nadachowski 1994, Silva and Strahl 1997, Rios et al. 2005
A. pipile Trinidad Hayes et al. 2009
Chamaepetes goudotii Colombia Londo ˜
no et al. 2007
Oreophasis derbianus Mexico Abundis-Santamar´
ıa and Gonza
ıa 2007
Ortalis canicollis Paraguay, Bolivia Brooks 1997, Mamani 2001
O. guttata Peru, Brazil Torres 1997, Begazo and Bodmer 1998, Haugaasen and Peres 2008
O. ruficauda Venezuela Silva and Strahl 1997, Schmitz-Orn´
es 1999
Penelope argyrotis Venezuela Silva and Strahl 1997
P. barbata Ecuador Jacobs and Walker 1999
P. jacquacu Peru, Brazil Terborgh et al. 1990, Torres 1997, Begazo and Bodmer 1998,
Haugaasen and Peres 2008, Barrio 2011
P. marail French Guiana Thiollay 1994
P. montagnii Ecuador, Colombia Nadachowski 1994, Creswell et al. 1999
P. obscura Brazil Guix et al. 1997
P. perspicax Colombia Kattan et al. 2006, 2014
P. purpurascens Venezuela Silva and Strahl 1997
Pipile cumanensis Peru Terborgh et al. 1990, Torres 1997, Begazo and Bodmer 1998,
Barrio 2011
P. jacutinga Brazil Galetti et al. 1997, Guix et al. 1997
The Condor: Ornithological Applications 118:24–32, Q2016 Cooper Ornithological Society
26 Cracid population densities G. H. Kattan, M. C. Mu ˜
noz, and D. W. Kikuchi
studies presented comparative data (Table 2). Begazo and
Bodmer (1998) collected data from hunters at 3 sites
classified as ‘‘protected area,’ ‘‘moderately hunted,’’ and
‘‘heavily hunted.’ Thiollay (1989) classified 3 sites as no
‘‘hunting,’ ‘‘near hunting area,’’ and ‘‘regularly hunted.’’
Mamani (2001) surveyed sites with subsistence hunting
and no hunting. Only Begazo and Bodmer (1998)
presented quantitative data on harvested birds, so we
used qualitative categories for analysis.
In addition to our paired hunting and no-hunting data,
we looked for an effect of hunting across our wider
modeled the natural logarithm of density as a function of
being in a hunted or nonhunted area, with ln(body mass)
included as a covariate. We included habitat type nested
within study site as a random effect to control for
variance in density across habitats and sites. We tested the
likelihood of this model against a model that did not
include hunting as a predictor, using the likelihood ratio
Body masses of the 27 cracid species included in this
sample varied by an order of magnitude, between 400 and
4,000 g. Cracines were larger than penelopines, and with
the exception of Nothocrax urumutum (Cracinae), whose
body mass (1,250 g) was in the upper range of penelopine
body masses, there was no overlap between the 2
In populations that had not experienced habitat
disturbance, fragmentation, or hunting, there was no
correlation between ln(mass) and ln(density) ( t
P¼0.12; Figure 1). We found no significant differences
between cracine and penelopine densities (t
¼0.94, P¼
0.36). Mean density (6SE) was 8.9 67.4 birds km
cracines (n¼8 species) and 17.7 69.4 birds km
penelopines (n¼16 species). However, cracine densities in
general were ,20 birds km
, except for Crax daubentoni,
which reached densities of 40 birds km
. The smaller
cracine species covered a broad range of densities that
included the lowest values observed in this subfamily
(Figure 2). Penelopine densities varied between 1 and 42
birds km
, but Ortalis canicollis reached densities of 170
birds km
. Several penelopines had densities of ,10 birds
(Figure 2).
Intraspecific and interspecific cracid densities varied
geographically over 2 orders of magnitude (1–100 birds
; Figure 2). For species with .1 density estimate in
what seemed to be adequate habitat with no hunting, there
were large differences in densities among localities. In
particular, densities were highly intraspecifically and
interspecifically variable among guans in the genus
Penelope.DensitiesofPenelope barbata in montane
habitats (unprotected but undisturbed cloud forest) in
Ecuador ranged from 2 to 17 birds km
(Jacobs and
Walker 1999). Other montane species reached compara-
tively high densities. For example, densities of P. perspicax
ranged from 10 to 42 birds km
in several protected sites
in the Colombian Andes (Kattan et al. 2014). An
Amazonian species, P. jaquacu, had a low density in a
TABLE 2. Studies comparing population densities of cracids among sites with different intensities of hunting.
Species Region No hunting
hunted Reference
Crax alector French Guiana 8.37 1.38
0.39 Thiollay 1989
Mitu tuberosa Peruvian Amazon 1.65 2.08 0.02 Begazo and Bodmer 1998
Ortalis canicollis Bolivian Chaco
44.6 8.7 Mamani 2001
O. canicollis Bolivian Chaco
172.1 41.9 Mamani 2001
O. guttata Peruvian Amazon 3.28 3.6 5.95 Begazo and Bodmer 1998
Penelope jacquacu Peruvian Amazon 5.46 5.46 0.22 Begazo and Bodmer 1998
Pipile cumanensis Peruvian Amazon 6.79 9.37 0.44 Begazo and Bodmer 1998
Near hunting area (see text).
Two different habitats.
FIGURE 1. Logarithmic relationship between mean density and
body mass for 24 species of cracids. Data from undisturbed,
nonfragmented sites. Each distinct shape indicates data from a
unique species.
The Condor: Ornithological Applications 118:24–32, Q2016 Cooper Ornithological Society
G. H. Kattan, M. C. Mu ˜
noz, and D. W. Kikuchi Cracid population densities 27
protected area (Manu National Park, Peru, 2 birds km
Terborgh et al. 1990), although one study reported
densities of ~20 birds km
(Torres 1997). In another
Amazonian locality (Rio Pur´
us), densities of this species in
different habitats were 0.2–4.4 birds km
(Haugaasen and
Peres 2008).
We found data for 3 species of chachalacas. Two of them
(O. canicollis and O. ruficauda) exhibited the highest
densities in the family, but the third one (O. guttata) had
low densities (3.3 birds km
in a protected area; Begazo
and Bodmer 1998). Densities of chachalacas varied in
different habitats. For example, in the Chaco region of
Bolivia, densities of O. canicollis were 43higher in tall
riverine forest than in drier scrub vegetation (Mamani
2001). In Venezuela, densities of O. ruficauda were higher
in agricultural areas (with fruit plantation fields and
deciduous forest in adjacent hills) than in deciduous and
semideciduous forest in a protected area (Schmitz-Orn´
Density variations and movements among habitat types
have also been reported in other forest-dependent species
in both cracid subfamilies (Table 3). For example, Bertsch
and Barreto (2008) reported that in central Venezuela, C.
daubentoni inhabited heterogeneous landscapes compris-
ing gallery and dry forest, but also used forest borders,
hedges, and open area. Birds reached very high densities
during the dry season in seasonally dry forest and gallery
forest, which suggests aggregation around water sources.
In open savanna, which may be considered a marginal
habitat, densities were low in both seasons.
Another cracine, Mitu salvini,wasstudiedinthe
northwestern Colombian Amazon, where Parra et al.
(2001) followed a family group for 6 mo. The group had
a home range of 72 ha that included riparian, flooded,
open, and mature forest. The birds temporally shifted their
patterns of habitat use in response to changes in food
resources, mainly the availability of fruit in flooded and
mature forest.
Patterns of habitat use at the population level have been
reported for P. perspicax in the Colombian Andes (Kattan
et al. 2014). Densities varied, from 10–18 birds km
medium-sized (500–700 ha), isolated forest tracts to 42
birds km
in a continuous forest of several thousand
hectares. These guans also used secondary forest, early
regeneration, and ribbons of vegetation along streams,
where densities were 10–40 birds km
. At one site, guans
congregated at a Chinese ash (Fraxinus chinensis)
plantation, where they reached densities of 100 birds
(Kattan et al. 2006, Rios et al. 2008). Guans
aggregated in large numbers at the ash plantation and
fed on ash foliage during the period of low fruit availability
in the forest (Mu˜
noz et al. 2007).
Two cracines were surveyed on islands. On Cozumel
Island, Mexico, densities of C. rubra were very low (0.9
birds km
), and 60% of records were obtained ,250 m
TABLE 3. Summary of studies reporting population densities of cracids in different habitat types.
Species and
site/conditions Habitat and density (birds km
) Country Reference
Crax daubentoni Gallery forest Dry forest Savanna Venezuela Bertsch and Barreto 2008
Dry season 161 44 13
Wet season 40 28 8
Ortalis ruficauda Continuous forest Agricultural–forest Urban–forest Venezuela Schmitz-Orn ´
es 1999
38 56 20
Penelope perspicax Old-growth forest Second-growth forest Riparian forest Colombia Kattan et al. 2014
Barbas 18 11
Bremen 11 42 17
Terra firme forest Va
´rzea Igap´
o Brazil Haugaasen and Peres 2008
P. jacquacu 4 0.2 0.6
O. guttata 1.5 1
Mitu tuberosum 1.6 3 1
FIGURE 2. Relationship between body mass and density for
cracids. This graph includes all data points, so a species may be
represented by .1 point (n¼46 density data points, n¼24
species). Filled circles are penelopines, and open circles are
The Condor: Ornithological Applications 118:24–32, Q2016 Cooper Ornithological Society
28 Cracid population densities G. H. Kattan, M. C. Mu ˜
noz, and D. W. Kikuchi
from a water source (Mart´
ınez-Morales 1999). By contrast,
on an island in the Caqueta River, Colombia, densities of C.
globulosa ranged from 11 birds km
in forest with a dense
understory to 19 birds km
in mature forest and 29 birds
in disturbed forest (Alarc´
on-Nieto and Palacios
2008). The density reported for this species in riparian
varzea in Bolivia was 3.4 birds km
(Hill et al. 2008).
Movements on a larger scale have been documented in P.
purpurascens and Chamaepetes unicolor in the Tilara
mountains of Costa Rica (Chaves-Campos 2003), by
quantifying changes in abundance at different elevations.
Both species breed in lower montane rainforest at 1,400 m
and apparently move downslope to elevations of 800 m
(premontane rainforest), with P. purpurascens going as low as
400 m at the transition of tropical wet forest to premontane
forest. These movements coincided with a general pattern of
altitudinal migration for bird species at this site.
In our analysis of studies with paired data on hunting
(Table 2), we found a significant effect of hunting on
population density (LRT; v2¼11.13, df ¼2, P¼0.004).
Tukey’s HSD revealed that although there was no
difference between areas with no hunting and areas with
low hunting (z¼0.41, P¼0.91), areas with heavy hunting
had significantly lower population densities than areas
with no hunting (z¼4.24, P,0.001). Indeed, populations
in areas with low hunting pressure also had higher
densities than those in areas with heavy hunting pressure
(z¼3.33, P,0.002). In our analysis of the entire dataset
that included both paired and unpaired sites, we found that
hunting continued to have a significant negative effect on
ln(population density) (v
¼6.01, P¼0.014). Hunting of
some species may favor other species. In the study of
Begazo and Bodmer (1998), O. guttata was more abundant
in hunted areas, because it is little hunted compared with
the other 3 (larger) species.
We found no clear relationship between body size and
population density in Cracidae. Some of the small species
exhibited low densities, and a few of the large species had
relatively high densities. In addition, the smaller penelo-
pines were not necessarily more abundant than cracines.
In analyses that included a broad range of body sizes (7
orders of magnitude) and density data obtained from
multiple localities, mean density of a species scaled to the
3/4 power of body mass (White et al. 2007). Our dataset
includes a body-mass range of only 1 order of magnitude,
which represents a small part of the global range. Thus, in
this context, the lack of correlation in our analysis is due to
regression scale. Cracids are highly frugivorous, but their
diets are very broad and plastic (Mu˜
noz and Kattan 2007).
Therefore, diet is unlikely to explain the observed
variability in population density.
Cracid population densities varied over 2 orders of
magnitude. In some cases, densities were relatively high,
even compared to small passerines. At several Neotropical
forests sites where bird densities have been estimated,
densities of nonpasserine species varied between 1 and 100
birds km
(Terborgh et al. 1990, Robinson et al. 2000,
Haugaasen and Peres 2008). Insectivorous passerine
densities also varied within the same range, although
many species had densities of ,20 birds km
2007, Kikuchi 2009). In Manaus, Amazonian Brazil,
median density of 228 bird species was 5 birds km
, and
55 species had 2 birds km
(Johnson et al. 2011). Thus,
cracid densities in general are not particularly low.
Intraspecific densities of cracids are geographically
variable, although few species have been evaluated at
more than 1 locality. Geographic variability in abundance
is a general phenomenon observed in birds and other
animals, as population densities respond to combinations
of factors that include variation in environmental condi-
tions and species interactions (Lundberg et al. 2000,
Sagarin et al. 2006). The factors that drive geographic
variability in cracid populations have not been investigat-
ed, but one possible factor is productivity related to
latitude, elevation, temperature, and precipitation patterns.
Habitat specialization is a dimension of rarity and an
important factor of vulnerability (Arita et al. 1990, Brooks
1998). Therefore, documenting spatial and temporal
patterns of habitat use is critical for conserving cracid
populations. Many cracids seem to be plastic and use
different habitats in heterogeneous landscapes. Variability
among habitats in the numbers of birds may reflect 1of 3
situations: (1) Different individuals show consistent
preferences for a particular type of habitat, where they
remain most of the time; (2) individuals move among
habitats over short-term periods; or (3) populations move
seasonally among habitats (e.g., Parra et al. 2001, Rios et al.
2006). Habitat shifts and local to regional movements in
response to food availability have been documented in
some avian species (Law and Dickman 1998, Renton 2001,
Holbrook et al. 2002, Haugaasen and Peres 2007).
Plasticity in habitat use promotes population stability
because it provides a range of resources and microclimates
at the landscape scale (Oliver et al. 2010). Thus, habitat
mosaics are important, and the protection of a single
habitat may be insufficient for the conservation of
populations (Law and Dickman 1998). The seasonal
patterns of habitat use in cracids require better documen-
Hunting is a major threat for cracids, which may
constitute the main hunted item in some ethnic commu-
nities (Begazo and Bodmer 1998). The risk is increased if
the hunted animals are rare (Brooks 1999). Even if
populations are not extirpated, heavy hunting reduces
population densities to the point where they may be
The Condor: Ornithological Applications 118:24–32, Q2016 Cooper Ornithological Society
G. H. Kattan, M. C. Mu ˜
noz, and D. W. Kikuchi Cracid population densities 29
demographically inviable because of Allee effects. The
impact of hunting will depend on harvest rates and the
extent of the area affected (Brooks 1999). For an area of
276 km
in Amazonian Peru, Begazo and Bodmer (1998)
estimated that harvest rates of M. tuberosa and P.
cumanensis were unsustainable, but harvest of P. jacquacu
was within sustainable levels. The persistence of hunted
populations also depends on the presence of nonhunted,
adjacent areas that may function as refuges or populations
sources, although the hunted area may be a population
sink (Powell et al. 1996).
Cracids are usually among the largest species in
Neotropical bird assemblages, but they are not necessarily
scarce—the rarest species are not necessarily the largest
ones. Despite differences in body size and terrestrial versus
arboreal habits, cracid species exhibit many ecological
similarities, such as highly frugivorous but opportunistic
and broad diets. Cracid densities are geographically
variable and exhibit temporal fluctuations as they move
among habitats tracking resources. Results from our small,
but geographically and taxonomically broad, sample
suggest that cracid populations respond idiosyncratically
to local factors. Therefore, researchers and managers
should be cautious when extrapolating data across species
or even among populations of the same species. Future
studies that aim to characterize cracid populations should
take into account possible intraspecific density variations
related to seasonality, local movements, and habitat
We thank Dan Brooks and an anonymous reviewer for helpful
comments on the manuscript.
Author contributions: G.H.K. and M.C.M. conceived the
idea. G.H.K. and M.C.M. collected data and conducted the
research. D.W.K. and G.H.K. analyzed the data. And G.H.K.
and D.W.K. wrote the paper.
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32 Cracid population densities G. H. Kattan, M. C. Mu ˜
noz, and D. W. Kikuchi
... Actualmente se encuentra restringida principalmente a bosques sub-andinos y andinos, entre 1000 y 2000 m s.n.m., en el piedemonte del valle del río Cauca en los departamentos de Risaralda, Quindío y Valle del Cauca. Sin embargo, existen registros por fuera de ese rango de elevación, desde 650 hasta 2690 m s.n.m. Kattan et al., 2015). ...
... El tercer núcleo poblacional corresponde a las cuencas de los ríos Nima y Amaime, y el cuarto núcleo denominado "Farallones de Cali", se localiza en el área amortiguadora del Parque Nacional Natural (PNN) Farallones de Cali, en el departamento del Valle del Cauca, en la vertiente oriental de la cordillera Occidental (Fierro-Calderón et al., 2018). A lo largo de esta distribución, hay estudios de densidad en los núcleos Risaralda-Quindío y Yotoco (Nadachowski, 1994;Kattan & Valderrama, 2006;2015;Ríos et al., 2006;2008;Banguera, 2009;Banguera et al., 2009;Ríos & Muñoz, 2010;Gutiérrez-Chacón et al., 2012). Los resultados de todos estos estudios se pueden observar resumidos y comparados en el Plan de manejo para la pava caucana (Fierro-Calderón et al., 2018). ...
... El principal resultado hallado en este estudio en términos ecológicos es el valor de la densidad poblacional en una localidad del núcleo de Farallones, lo que permite realizar comparaciones con los otros núcleos que ya cuentan con esta información (Nadachowski, 1994;2015, Roncancio-Duque & López, 2007Ríos et al.,2008;Banguera, 2009;Banguera et al., 2009;Gutiérrez-Chacón et al., 2012). ...
Full-text available
La pava caucana (Penelope perspicax) es un ave endémica de las laderas del valle geográfico del río Cauca en Colombia, considerada en peligro de extinción. La pérdida de hábitat y la cacería han sido sus principales amenazas, lo que ha generado la reducción y aislamiento de sus poblaciones. El objetivo de este estudio fue determinar la densidad poblacional en una localidad en los Farallones de Cali y desarrollar modelos de ocupación, para evaluar factores que expliquen el uso de hábitat de la especie. Obtuvimos una densidad de 9, el valor más bajo de los estimados disponibles para la especie; además, encontramos una relación estrecha entre el área de cobertura boscosa y el uso del hábitat de la especie. Los resultados indican la necesidad de conservar los remanentes de bosque y mantener la conectividad, ya que a pesar de que la especie puede utilizar gran variedad de hábitats, la probabilidad de uso aumenta en relación a las áreas disponibles de bosque. Recomendamos que se aumenten los esfuerzos de muestreo en este núcleo poblacional, asegurando variabilidad temporal y espacial, con el fin de contar con mejor información para su manejo en este núcleo.
... En el valle geográfico de río Cauca se distribuyen varias especies de crácidos, entre ellos, la guacharaca colombiana (Ortalis columbiana) (Kattan, et al., 2016). En esta zona las coberturas vegetales naturales se han reducido en cerca del 90 % pasando de alrededor de 14.000 km 2 a cerca de 1.600 km 2 , con un poco más de 900 fragmentos de bosque de 183 ha en promedio (coeficiente de variación, CV=759), los cuales tienden a ser alargados (índice medio de forma de 2,6 según cálculos del autor para el presente trabajo). ...
... El componente que más aportó a la varianza de la densidad fue la tasa de encuentro, con un 90,3 %, seguido por la probabilidad de detección, con 6,7 %, y el tamaño de grupo, con 3,0 %. La densidad poblacional de O. columbiana en este muestreo resultó mayor comparada con algunas estimaciones de especies de crácidos de otros géneros, entre ellos, Crax allector (Thiollay, 1989), Mitu tuberosa (Begazo & Bodmer, 1998), Penelope jacuaco (Begazo & Bodmer, 1998) y Pipile cumanensis (Begazo & Bodmer, 1998), incluidas las estimaciones en zonas sin presión de cacería en hábitats continuos (Kattan, et al., 2016). También resultó mayor a la densidad de Crax daubentoni en sabanas tanto en la época seca como en la húmeda (Bertsch & Barreto, 2008). ...
... Comparada con O. guttata, especie más emparentada filogenéticamente con O. columbiana (Salaman, et al., 2001;Donegan, et al., 2010), la densidad fue entre 4 y 20 veces mayor (Haugaasen & Peres, 2008), lo que se podría explicar por la menor productividad de la Amazonia comparada con los bosques andinos, y la mayor diversidad de especies en los bosques continuos que pueden competir en algunas dimensiones del nicho con las Ortalis (Hutchinson, 1957). Sin embargo, es esencial adelantar estudios inferenciales (comparativos o que evalúen relaciones) de O. columbiana controlando factores alineados para poder determinar con mayor confianza aquellos que determinan la abundancia de esta especie y que ayuden a comprender la gran variación en este indicador para la familia (Kattan, et al., 2016). ...
Full-text available
Las especies endémicas con requerimientos ecológicos muy específicos o bajas densidades poblacionales son prioritarias en términos del diagnóstico de su estado de conservación. Para conocer el de una especie es necesario determinar su abundancia y su tendencia en el marco de programas rigurosos de monitoreo. El territorio del Valle del Cauca ha sido muy intervenido y actualmente solo existen remanentes de bosque, entre ellos, la Reserva Natural Bosque de Yotoco (RNBY), en el municipio de Yotoco. Allí habita Ortalis columbiana, especie endémica de Colombia, cuya densidad no ha sido documentada. En ese contexto, se estimó la densidad poblacional para conocer el estado de conservación de esta especie en la RNBY mediante el método de muestreo por distancia con 32 transectos lineales y más de 200 km de esfuerzo de muestreo. Se encontró una densidad poblacional de 19,2 ind/km2 (IC95%: 9,8-37,6) con un tamaño medio de grupo de 1,56 individuos (IC95%= 1,4-1,8). Este resultado es relativamente mayor que las estimaciones hechas para otras especies de crácidos, únicos referentes de comparación, y sugiere que la población sería de cerca de 100 individuos solo en la Reserva. Este tamaño poblacional podría considerarse bajo para mantener una población viable, no obstante, es importante considerar su presencia y abundancia en los agroecosistemas adyacentes para llegar a conclusiones sobre su viabilidad poblacional.
... The present study complements previously reported information by addressing daily and seasonal activity patterns and providing additional insights into Bare-faced Curassow social organization, parental care, adult sex ratio, and offspring sex ratio for the same study area and time period. The study also considers the potential effects of strong seasonal flood pulses in the area [36] on these patterns, as the movements of different cracids are known to be related to the seasonality of rainfall or resource availability [37]. ...
... Kattan et al. [37] indicated that the movement patterns of several cracids (Yellowknobbed Curassow, Crax daubentoni; Salvin's Curassow, Mitu salvini; and Cauca Guan, Penelope perspicax) are related to the seasonality of rainfall or resource availability, congregating around water sources during the dry season or around seasonally abundant food sources. Seasonal periods in the Pantanal are determined by the annual water regime [36]. ...
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Citation: Senič, M.; Schuchmann, K.-L.; Burs, K.; Tissiani, A.S.; de Deus, F.; Marques, M.I. Activity Patterns, Sex Ratio, and Social Organization of the BareFaced Curassow (Crax fasciolata) in the Northern Pantanal, Brazil. Birds 2023, 4, 117-137. https://doi. Simple Summary: For the majority of tropical birds, basic life history information is still missing and holds mostly for tropical forest species. Among these are the members of guans, chachalacas, and curassows, a New World avian family known as cracids. In our study, conducted in a protected area in the northeastern Pantanal of Brazil, where human impacts were low, we investigated the seasonal activity, social organization, and sex ratio of the Barefaced Curassow using camera traps. Strong seasonal inundation pulses are characteristic of the study area and influence vegetation, resource, and water seasonality, causing differences in seasonal activity behavior patterns. The daily activity of the Barefaced Curassow differed between forest-and savanna-dominated areas but did not differ by sex, seasonal period, or presence of offspring. Such population studies in protected areas may serve as a "template" to plan more appropriate conservation and area management strategies that are applicable locally and beyond. Abstract: Among Neotropical cracids (Galliformes), many taxa are declining rapidly in population size and facing local extinction. However, in the Brazilian Pantanal, several species occur sympatrically and in abundant numbers to allow for long-term studies. Therefore, the study was intended to collect data and statistically evaluate the life history patterns of Barefaced Curassow (Crax fasciolata), a high-conservation-priority species. Additionally, the effect of applying commonly used independence filters on camera trap data was evaluated. The study was conducted in the SESC Pantanal, Baía das Pedras, Mato Grosso, Brazil, a private protected area of approximately 4200 ha. Between July 2015 and December 2017 (4768 sampling days), 37 sampling locations were monitored with camera traps placed in a regular grid with a spacing of 1 km. Crax fasciolata was detected at 26 (70.27%) of them, with 357 independent captures (554 individuals). Capture success differed among the four seasonal periods, being highest during the receding and lowest during the high-water period. The seasonal difference was more pronounced in the savanna, with significantly lower activity during the rising period and higher activity during the receding period, while it was more uniform in forest-dominated areas. Groups with offspring were more active during the period of receding water, indicating the peak of reproductive activity in the months before. The daily activity of the species followed a bimodal pattern, with peaks between 06:00 and 07:00 and 16:00 and 17:00. Daily activity rhythms were similar when compared between seasonal periods, sexes, and adults with or without offspring and differed between two habitats (more homogeneous in the forest). The mean detected group size was 1.55 ± 0.81 SD, with four animals exhibiting the largest observed aggregation. Larger unisexual aggregations of adults were not observed. The offspring sex ratio was significantly female-skewed at 0.51:1.00, while the adult sex ratio was considered equal at 1.05:1.00 (male:female). The use of different independence filters did not alter the BFC general activity pattern estimates. Cracids can be considered important bioindicators of habitat quality. The results of this study outline the importance of the Pantanal as a stronghold for this species and the privately protected areas with low anthropogenic activity as highly beneficial to its populations.
... In contrast, a density of 0.4 to 1.2 individuals/km 2 was (1997), which is lower than that of the Cozumel Curassow. In general, our population density estimates are among the lowest for any species in the Cracidae family, which are around 20 individuals/km 2 (Chalukian 1997;Ríos et al. 2005;Bertschand and Barreto 2008;Kattan et al. 2016), even in places where hunting exists (Terborgh et al. 1990;Bezerra et al. 2019). The density of the Cozumel Curassow continues to be among the lowest for the family. ...
... In the present study, all the sightings were in five of the 16 transects located in the center and southeast sections of the island, except for an observation of a male to the north (the first record in that area). As reported for mainland cracids (Kattan et al. 2016), it is possible that the Cozumel Curassow does not present habitat selection plasticity, explaining why its presence is limited to tropical semi-deciduous forest. Such affinity or dependence could be the result of different ecological and evolutionary processes, such as competition, predation, or association and interaction with other species such as the tree species considered in this evaluation (Solomon 1949;Bezerra et al. 2019;Ortega-Gamboa 2019). ...
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The Cozumel Curassow (Crax rubra griscomi) is a critically endangered endemic bird from Cozumel Island, Mexico. After it was believed to be extinct, it was rediscovered in 1994. Its population status was assessed in 1994–1995, and later in 2005, predicting a population decline over the next four decades. A new evaluation of its population size was carried out in 2017 and 2019. Some of the main factors that affect the population size of this cracid were identified with a generalized linear model. With a line transect sampling effort over 360 km, a population size of 499 ± 172 individuals was estimated in the tropical semi-deciduous forest occurring in the island, which was slightly higher compared to previous population evaluations. The distance to water bodies was significantly associated with the population size of the Cozumel Curassow, as well as the abundance of some species of fauna and flora. By modeling various scenarios, population viability was assessed over a period of 100 years, predicting a relatively stable population size with great variability depending on scenarios. However, as estimated in previous studies, given its small population size and continued threats, the Cozumel Curassow continues to be endangered.
... One of the most important families of Neotropical birds is the Cracidae family, belonging to the order Galliformes, of which six genera and twenty-six species occur in Brazil (Pacheco et al., 2021). Body size, ground displacement, habitat loss and hunting (Kattan et al., 2016) make this one of the most endangered bird families in the world (Candido et al., 2011;Frank-Hoeflich et al., 2007). Cracids represent a significant portion of vertebrates in the habitats where they live, contributing to various ecological processes, including in their diet many fruits and seeds of different sizes (Muñoz and Kattan, 2007). ...
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The Atlantic Forest is a threatened biodiversity hotspot. Anthropogenic and environmental factors affect this biodiversity, including floristics and, consequently, the seed dispersal syndrome. The objective was to evaluate the influence of environmental factors on floristic composition, seed dispersal syndrome and potential for wild fauna refuge, especially birds of the Cracidae family, in a Private Reserve of Natural Heritage (RPPN) in the Atlantic Forest. The study was carried out in a forest fragment of 631 ha in the RPPN Fazenda Macedônia in Ipaba, Minas Gerais, Brazil. Twenty-three plots (10 m x 50 m) were inventoried at three sampling levels with the plots being selectively distributed, considering the different geoenvironments. Environmental factors were divided into edaphic (soil chemical and physical) and landscape (altitude, slope, terrain exposure and edge distance) variables. Species composition and plot groupings by smallest dissimilarity were calculated. The dispersal syndrome and the type of zoochoric dispersal were determined for tree species. The species dispersed by birds had records of occurrence in the verified cracid diet. Two hundred and forty-nine species from 138 genera and 46 tree families were recorded. The dissimilarity between plots ranged from 0.4 to 1.0 forming four groups. Floristic composition was influenced by soil variables (soil pH, available potassium and magnesium, exchangeable aluminum, effective and potential CEC, remaining phosphorus, organic matter and silt) and landscape (altitude). The zoochoric dispersal syndrome was the most frequent, with ornithochory (68.09%) being the most important within this group. In the RRPN, 35 species of tree were recorded in the cracids diet. Tree species composition of varied with edaphic variables and with altitude. The wide distribution of species recorded in cracid diets reaffirms the fragment's potential for the establishment and conservation of these birds, highlighting the importance of creating and protecting private conservation areas, such as the RPPN Fazenda Macedônia and corridors among all forest private areas belonging to the CENIBRA company in that landscape.
... La familia de los crácidos (Cracidae, Galliformes) agrupa a paujiles, pavas y chachalacas (Sedaghatkish y Brooks, 1999). Los crácidos, presentan dietas amplias, pero básicamente se alimentan de frutas y se los considera importantes dispersores de semillas (Kattan et al., 2016;Muñoz y Kattan, 2007). Este grupo incluye al paujil nocturno Nothocrax urumutum, el cual se distribuye en los bosques tropicales amazónicos y de estribación al sur de Venezuela, este de Colombia y Ecuador, noreste de Perú y oeste de Brasil (BirdLife International, 2016;Parker, 2002). ...
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The Nocturnal Curassow, Nothocraxurumutum, is one of the most elusive land bird species in the mainland and foothills of the Amazon. In order to evaluate the pattern of activity of the Nocturnal Curassow and compare it with 3 species of competitors and 3 species of predators, we carried out surveys in three locations in the western Ecuadorian Amazon. Between July and October 2015 to 2017, 90 camera traps located at random 1 km from each other, in an area of 90 km2 were used. We generated activity patterns by means of Kernel density curves and we estimated the overlap coefficient between competitors and predators of the Nocturnal Curassow. One hundred percent of the records were daytime, with peaks of activity between 06:30-08:30 and 14:00-18:00 h. Four species presented overlapping coefficients with the Nocturnal Curassow > 60%, while 2 species did not exceed 44%. The pattern of activity of the Nocturnal Curassow was significantly different with respect to the gray-winged trumpeter, red brocket, ocelot, and tayra, and it did not change with the presence of black aguti and domestic dog. Our results support the observations of bimodal, solitary or pair behavior and the temporary partitioning of the Nocturnal Curassow, as mechanisms to decrease or avoid encounters with competitors and predators. Keywords: Camera traps; Competitors; Predators; Activity pattern; Sociability
... Cracids (curassows, guans, and chachalacas) comprise a group of large, forest-dwelling frugivorous birds and represent the most threatened avian family in the Neotropics (Brooks, 2006a;del Hoyo et al., 1994;Kattan et al., 2016;Strahl et al., 1997b), 50% of the species within this family being listed as "Vulnerable" or at higher risk of extinction (IUCN, 2018). Due to decreasing population trends, the Black Curassow Crax alector was uplisted in 2012 from "Least Concern" to "Vulnerable" in the IUCN red list (Birdlife International, 2016;A3c). ...
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Cracidae is the most threatened avian family in the Neotropics, mainly because of habitat destruction, heavy hunting pressure and poaching. In French Guiana, Black Curassows are heavily hunted, although basic knowledge of the ecological and demographical traits of the species remains limited. Such a gap prevents any attempt to assess the impact of hunting and to help stakeholders to develop proposals ensuring hunting sustainability. The spatial relationship between animals and their habitat is important for conservation management, being related to population densities through complex patterns. Here, we report on a radio-tracking study of Black Curassows in tropical primary rainforest, in Nouragues National Reserve, French Guiana. The aims of the study were to estimate home range size and its variation across seasons, and to quantify movement patterns of the birds. We captured and fitted VHF tags to four adults, and tracked them for 10 to 21.5 months. Daily movements were recorded, and home ranges estimated using the Kernel Density method, for two consecutive wet seasons and one dry season. Using 95% and 50% Kernel densities, the average annual home range and core area were 96.3± 32.6 ha (SE) and 22.8 ± 2.8 ha respectively. Home ranges appeared spatially stable over the two years, and overlapped between neighbouring groups. During the dry season, Black Curassows did not migrate but tended to enlarge their home range, with greater daily movements and higher home range overlap. Although additional data are still needed, our results can help to improve the knowledge and management of this poorly studied species.
... These findings are similar to those of Botelho et al. (2012) for medium and large mammals in HFR. Although they tend to become rarer, large cracids appear to be able to persist in areas with moderate hunting pressure (Barrio 2011, Kattan et al. 2016. The presence of Crested Morphnus guianensis and Harpy Eagles Harpia harpyja, which are also targeted by hunters (Trinca et al. 2007, Muñiz-López 2017 is a further indication of the favourable conditions. ...
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Humaitá Forest Reserve (HFR) is a forest fragment in the state of Acre, Brazil. Between 2009 and 2019, this fragment has been inventoried by multiple ornithologists and birdwatchers. To provide a comprehensive list of the avifauna of HFR, we compiled all of the available data, including published reports and recent, unpublished surveys. The list includes 356 bird species belonging to 60 families and 23 orders. This species richness is the greatest recorded in those forest fragments that have been inventoried in eastern Acre. We found that HFR is an important site for the conservation of many threatened species, and migrants, as well as poorly known species with a restricted geographic distribution, such as Semi-collared Puffbird Malacoptila semicincta, Goeldi’s Antbird Akletos goeldii, Rufous Twistwing Cnipodectes superrufus and Acre Tody-Tyrant Hemitriccus cohnhafti.
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Large ground-dwelling Neotropical gamebirds are highly threatened by habitat loss and hunting, but conservationists rarely attempt to distinguish between these two threats in the management of populations. We used three different types of species records to determine the status (i.e. persistence level) of the Endangered red-billed curassow Crax blumenbachii in 14 forest remnants in north-east Brazil, as either persistent, precarious or extirpated. We related these persistence levels to variables measured in a 2-km buffer radius, including variables associated with habitat quality (proportion of forest cover, length of rivers, patch density, distance from rivers) and hunting pressure (proportion of cacao agroforests and farmlands, length of roads, total area occupied by settlements, distance from roads and from settlements). Curassows were more persistent in forest patches located (1) more distant from settlements, (2) in landscapes with few settlements, (3) in landscapes with a high incidence of roads, (4) in a mosaic with a high proportion of forest, shaded cacao agroforest and farmland, and (5) more distant from other forest patches. Hunting pressure potentially exerts more influence on persistence than habitat quality: (1) hunting pressure submodels had a higher explanatory power than habitat quality submodels, (2) final models comprised four hunting pressure variables but only two habitat quality variables, and (3) hunting pressure variables appeared in all models whereas habitat quality variables appeared in only one final model. If hunting pressure is driving declines in curassows, regions with low human presence and a high proportion of forest cover are recommended for establishing new reserves.
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We studied the habitat, breeding, social behavior, and vocalizations of the Colombian endemic Cauca Guan (Penelope perspicax) in the Otún Quimbaya Sanctuary for Flora and Fauna in Risaralda Department on the west slope of the Central Andes. This guan inhabited natural forests as well as forest plantations, where it fed mostly on fruits and foliage high in the trees and captured invertebrates on the ground while following army ants (Labidus praedator). Based on the frequency of vocalizations, wing-whirring, and detection of chicks, we concluded that breeding occurred from January to June, coinciding with a peak of fruit abundance, which was followed by a molting period. Clutch size was two, and the young remained with their parents until subadult age, i.e. ca. one year after hatching. The guans lived in small family groups, but on rare opportunities as many as 30 individuals ocked together. We did not detect aggressive behavior, territoriality, xed roost sites, or xed foraging routes. Although our results suggest that the Cauca Guan tolerates disturbed habitats, and that this population is carrying out all of its vital activities within the Sanctuary, we deem it important to consider the effects of fragmentation, isolation, and hunting as continuing threats to this species.
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Although exotic species may have a negative impact on native organisms, they can in some cases provide abundant resources. Use of these resources may have important implications for habitat use, movement, and space requirements of native animals, and ultimately for population dynamics. We describe the diet of a population of the narrowly endemic Cauca Guan (Penelope perspicax) in the Colombian Andes. This guan demonstrates plasticity in its eating habits, feeding on an exotic tree species during periods of food scarcity. Based on direct observations and analysis of fecal samples over a one-year cycle, we found that guans fed on 89 species of fruits but also included foliage, flowers, and invertebrates in their diets. Guans fed on fruit species in proportion to their availability but favored some species with high fruit production or prolonged fruiting. Fruit availability, measured both in numbers of species and biomass, varied throughout the year, with a low in September–December. During the period of low fruit availability, guans congregated in large numbers at a Chinese ash (Fraxinus chinensis) plantation, where they fed on young leaves in large quantities. Ash was planted at this site over 40 years ago as part of a reforestation program, and plantations are invaded by native vegetation. Guans are abundant at this site, and seasonal consumption of ash foliage, a concentrated and abundant food source, may have influenced local population dynamics.
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Lower Caquetá river, southeastern Colombia, intensive surveys were carried out in order to locate other remaining populations of the species, and to estimate their size and status for planning a program in which biologists and local people could work together to protect the species, critically endangered in Colombia. By doing line transects, density and population size were calculated for every surveyed site where the species was found. In Mintí island, where density is 19 ind/km2, population may reach up to 140 individuals. Density is higher in Amaure island but, as its area is only about 1.2 km2, no more than 35 individuals could be living there while, in El Brazuelo island, there are only about 20 individuals. The discovery of these new populations in Colombia improves conservation opportunities for the Wattled Curassow but it does not change the status for the species which remains critically endangered.
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The Cracidae are a Neotropical family of 50 species of galliform birds, many of which are threatened. Through a literature review, we evaluated current knowledge of cracid food habits and established general dietary patterns. Diet has been relatively well documented for 17 species, anecdotal information is available for 19 species, and no information is available for 14 species. Fruit is the most important food category for cracids, and 672 species in all fruit types (e.g., drupes, berries, arillate fruits) are reported. For most species, the most important plant families in their diets are also the most common and diverse families in Neotropical forests. Foliage, flowers and animal foods (invertebrate and vertebrate) are also common items in cracid diets. Consumption of foliage, in particular, is widespread but folivory has not been adequately studied in these birds. Penelopinae usually pass seeds intact through the digestive tract and are potential seed dispersers. Cracinae, in contrast, have strong gizzards and usually feed on large seeds, with only small seeds passing intact. In general, cracids seem to have broad and generalist diets, although restricted diets in response to local conditions have been reported. Few studies have evaluated seasonal and habitat variations in resource availability and cracid responses to such variation. An understanding of patterns of resource use and availability is essential for understanding habitat use, space needs and population dynamics of Cracids.
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Amazonian forest bird communities are among the richest in the world. Even so, relatively little is known about the organization of the entire avian community at local scales or about differences across Amazonia. These are fundamental data not only for understanding the processes generating and maintaining tropical diversity, but also as a baseline for evaluating anthropogenic changes to Amazonian forests. Here we provide a description of the entire bird community for a 100 ha plot of terra firme forest at the Biological Dynamics of Forest Fragments Project, near Manaus, Brazil, based on spot-map and mist net surveys augmented by additional field and analytical techniques. Although our results are from a single plot surveyed in a single year, our methods and interpretation reflect nearly 30 years of ornithological research at the site. We found 228 species on the plot, of which 207 were considered part of the core regional avifauna. Median density was five individuals/100 ha. Only 13 species (6% of the core species) had densities ≥ 20 individuals on the plot, although 55 species (27%) had ≤ 2 individuals. No species had territories smaller than 3 ha; median territory size was 11 ha for the 103 species for which we could make reasonable estimates. Measured by numbers of species or individuals, the plot was dominated by insectivores (54% of species, 62% of individuals). Biomass, however, was dominated by frugivores and granivores (59%). Compared to available data from other Amazonian forests, our site appears to have comparable richness of a similar set of species, but lower density and greater patchiness. Our results suggest that the area required to support populations of many species will be even greater in central Amazonia than in western Amazonia.
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We studied avian breeding and molting activity in relation to rainfall, temporal fluctuations in food resource abundance, and food exploitation by birds, in four arid and semiarid tropical habitats in Venezuela. Twice a month we used mist to monitor changes in breeding and molting conditions of captured birds and forced them to regurgitate to determine their diet and feeding guild membership. Food abundance was assessed by measuring the flowering and fruiting seasonality of marked plants and by evaluating arthropod abundance with four different trapping methods. Flowering activity was limited largely to the wet season. Fleshy fruits, although produced year—round, were also more abundant in the rainy period. Anthropod abundance followed the same general pattern with numbers highest in the wet season and lowest in the dry season. Birds of all feeding guilds predominantly bred and molted during the wet season, synchronously with the highest abundance of most food resources. However, the diet analysis revealed a higher occurrence of arthropods coupled with a sharp decrease in the intake of vegetable matter during birds' breeding season. Consequently, we suggest that arthropod abundance is a crucial factor governing the timing of breeding activities, even in species that normally include a high proportion of nectar and fruits in their diet. We also postulate that, in tropical habitats receiving >1500 mm of rain per year, breeding in nectarivores and frugivores in the dry season may be related to the lower reduction in arthropod numbers over the less severe drought period.
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Resumen. – Cambios en la abundancia de la Pava Crestada (Penelope purpurascens) y la Pava Negra (Chamaepetes unicolor) a través de un gradiente altitudinal en Costa Rica. – Hice un monitoreo de la abundancia de la Pava Crestada (Penelope purpurascens) y de la Pava Negra (Chamaepetes unicolor) en tres dife-rentes elevaciones en la Cordillera de Tilarán, Costa Rica, durante 1998. Ambas especies fueron más abun-dantes a 1400 m s.n.m. (bosque lluvioso montano bajo) durante su época reproductiva. Después de la época reproductiva, su abundancia disminuyó a esa altitud y se incrementó a una menor elevación: 800 m (bosque lluvioso premontano). Además, la abundancia de la Pava Crestada se incrementó a 400 m (bosque húmedo tropical transición a premontano) durante la época no reproductiva. Estos cambios en abundan-cia coincidieron con el patrón de migración altitudinal que exhiben especies migratorias altitudinales bien confirmadas en la vertiente Caribe de Costa Rica, por lo que podrían reflejar que ambas especies de pavas son migratorias altitudinales. Abstract. – I monitored the abundance of Crested (Penelope purpurascens) and Black (Chamaepetes unicolor) guans at three different elevations on the Caribbean slope of Cordillera de Tilarán, Costa Rica, during 1998. Both species were more abundant at 1400 m a.s.l. (lower montane rain forest) during their breeding season. After the breeding season, their abundance decreased at that altitude and increased at a lower ele-vation: 800 m (premontane rain forest). Also, Crested Guan abundance increased at 400 m (tropical wet forest transition to premontane) in the non-breeding season. These changes in abundance coincided with the pattern of altitudinal migration that well-confirmed altitudinal migrant species exhibit on the Carib-bean slope of Costa Rica, and might reflect that both species of guans are altitudinal migrants. Accepted 8 September 2002.
To help fill the gap in detailed knowledge of avian community structure in tropical forests, we undertook a census of a 97-ha plot of floodplain forest in Amazonian Peru. The plot was censused over a 3-mo period spanning the 1982 breeding season. The cooperative venture entailed @?12 person-months of effort. Conventional spot-mapping was the principal method used, but several additional methods were required to estimate the numbers of non-territorial and group-living species: direct counts of the members of mixed flocks, saturation mist-netting of the entire plot, opportunistic visual registrations at fruiting trees, determination of the average size of parrot flocks, color banding of colonial icterids, etc. Two hundred forty-five resident species were found to hold territories on the plot, or to occupy all or part of it. Seventy-four additional species were detected as occasional-to-frequent visitors, wanderers from other habitats, or as migrants from both hemispheres. By superimposing territory maps or the areas of occupancy of individual species, we determined that point (alpha) diversities exceeded 160 species in portions of the plot. About 1910 individual birds nested in 100 ha of this floodplain forest, making up a biomass conservatively estimated at 190 kg/km^2. The total number of breeding birds was equivalent to that in many temperate forests, but the biomass was about five times as great. Predominantly terrestrial granivores contributed the largest component of the biomass (39%), followed by largely arboreal frugivores (22%). Considering only insectivores, the biomass (34 kg/km^2) is somewhat less than that in the forest at Hubbard Brook, New Hampshire (40 kg/km^2), although it is greater (55 kg/km^2) if one includes omnivores. The number of insectivores was considerably less than at Hubbard Brook, due to their 60% larger average body size (32 vs. 20 g). Even though a large majority of the species were patchily distributed, the 97-ha plot was found to include 99% of the bird species that regularly occupy mature floodplain forest at Cocha Cashu. The most abundant species occupied territories of 4-5 ha, and 84 species (26%) had population densities of @<1 pair per square kilometre. Of these, 33 (10% of the total community) were judged to be constitutively rare (i.e., having low population densities everywhere), rather than being merely locally rare. Many of these are predicted to be vulnerable to forest fragmentation and disturbance. Comparison of these results with those from other tropical forests proved difficult due to a lack of standardized methodology.