Journal of Tropical Ecology (2009) 25:605–613. Copyright © Cambridge University Press 2009
doi:10.1017/S0266467409990289
Population dynamics of the black-cheeked gnateater
(Conopophaga melanops, Conopophagidae) in southern Brazil
Andre´ Magnani Xavier de Lima∗,† and James Joseph Roper†,1
∗ Universidade Federal do Parana´, Graduate Program in Ecology and Conservation, CP 19031, Curitiba, Parana´, 81531-980 Brazil. Email: andremxlima@uol.com.br
† Instituto de Pesquisa e Conservac¸a˜o da Natureza – Ide´ia Ambiental, Rua Euclides Bandeira, 1635, Curitiba, CEP 80530-020, Brazil
(Accepted 10 August 2009)
Abstract: Population structure and dynamics of the black-cheeked gnateater (Conopophaga melanops) were studied
at Salto Morato Nature Reserve, in Parana´, southern Brazil, from October 2006 to September 2007. Territory size
and population density, breeding season (timing and length), reproductive success and annual survival rates were
estimated from sightings of 18marked adult birds and the success of 18 nesting attempts. The black-cheeked gnateater
is socially monogamous and territorial, with a breeding-season length of approximately 3 mo beginning in early
October. Predation caused most nest failures, nest survival was 0.96 d−1 and apparent annual nesting success was
22%, resulting in annual productivity of 0.36 individuals per adult. Apparent adult annual survival was ∼0.44 y−1.
Seventy-five per cent of fledglings survived at least 2 mo after fledging. Two methods of estimating population growth
rate suggest very different rates: r = −0.04 (∼ stable), or λ varies between 0.475–0.616 (declining). Yet, low apparent
adult survival suggests that territories are not permanent, perhaps abandoned after nest failure. We find that by
estimating population growth, even in short-term studies, testable hypotheses can be generated that will allow better
understanding of population dynamics.
Key Words: Atlantic Forest, Conopophaga, gnateater, growth rate, productivity, population dynamics, survival
INTRODUCTION
Estimating population parameters, such as reproductive
success and survival, are first steps towards understand-
ing population dynamics. In tropical and subtropical
America, while reproductive success has been measured
in some bird species (Martin 1995, Morton & Stutchbury
2000, Robinson et al. 2000a, Roper 2006), population
dynamics of most species are completely unknown (but
see Rangel-Salazar et al. 2008). Some regions, such as
the Brazilian cerrado (savanna) (Duca & Marini 2005a,
b; Lopes & Marini 2006, Marini & Garcia 2005) and
northern Argentina (Auer et al. 2007), are gradually
becoming better known with respect to breeding biology,
butmuch isyet tobedone (Lyon et al.2008,Martin1995).
Typically, few attempts are made to infer population
trends in these studies, however, those trends are what
we need to better understand, considering the ever
increasing threats from habitat loss and other anthropic
environmental changes (Aleixo1999, Brooks&Balmford
1 Corresponding author. Email: jjroper@gmail.com
1996, Christiansen & Pitter 1997). Apparently, data are
considered insufficient to adequately estimate population
trends and therefore estimates of population parameters
are often not forthcoming.
Evolution of avian life histories has a long history of
debate, much of which was instigated from observations
of birds in tropical America (Ricklefs 2000). Nonetheless,
today tropical, subtropical and southern temperate
regions are poorly studied and consequently, poorly
understood in terms of life histories that may inform
that debate. The Atlantic Forest of south-eastern Brazil
is rich in species in a wide variety of taxa, including
many endemic species of plant andanimal (Machado&da
Fonseca 2000, Morellato & Haddad 2000). Climatically,
the region is a transition between tropical and southern
temperate realms, thus understanding life histories of
species here may provide important information for
understanding avian life-history evolution.
Gnateaters, in the family Conopophagidae, are in this
group of poorly studied southern birds, including eight
species in the genus Conopophaga and two in the genus
Pittasoma (Rice 2005, Ridgely & Tudor 1994). They
comprise relatively small, stocky and plump birds of the

606 ANDRE´ MAGNANI XAVIER DE LIMA AND JAMES JOSEPH ROPER
forest understorey. Exclusively South American, these
birds are poorly known because they are relatively quiet
and forage on the forest floor, much like typical antpittas.
Here, in a first attempt at estimating population
parameters, we describe the annual cycle of reproduction
and survival of the black-cheeked gnateater (Conopophaga
melanops, Vieillot 1818), a species endemic to theAtlantic
Coastal Forest of eastern Brazil. We use these data to
estimatepopulationgrowth rates andexamine thepossib-
ility that testable hypothesesmay be developedwith even
short-term data and which may direct future research.
METHODS
Study site and species
The black-cheeked gnateater was studied in the Salto
Morato Nature Reserve (SMNR, 25◦13′S, 48◦17′W), in
coastal lowland tropical forest, in the state of Parana´,
Brazil (Figure 1). The reserve, comprising approximately
2300ha, is in a largermatrix ofmixed successional stages
of Atlantic Forest (> 400 000 ha), contiguous with the
largest area of well-preserved Atlantic Forest in South
America (FBPN2001).While technically subtropical due
to latitude, the forest is tropical humid, with an annual
average temperature of ∼22 ◦C and precipitation of
2000 mm (Maack 2002). The annual cycle may be
divided into two seasons. May–September is cooler and
drier, with temperatures varying between 2–35 ◦C and
10% of the annual rainfall. October–April is warmer and
wetter and temperature varies from 8–38 ◦C with 90% of
the annual rainfall (SIMEPAR, data provided on request,
Figure 1. Study area at Salto Morato Nature Reserve, in coastal Parana´,
in southern Brazil.
http://www.simepar.br/). The study area comprised
∼20 ha within the reserve, near a river and with varying
topography (30–100melevation)andamixof vegetation
from relatively young floodplain to mature forest.
We wished to attempt an examination of any
associationof breeding seasonwithclimate.Thus, climate
data from the local weather station (SIMEPAR, the
nearest station ∼40 km, in Paranagua´) were used. Day-
length, however, is an astronomical phenomenon, and
so we used tabulated data found on-line (http://aa.
usno.navy.mil/data/docs/RS_OneYear.php). Rainfall is
quite variable and so we used crude weekly rainfall and
smoothed rainfall (the average rainfall of the week in
question plus the preceding and followingweek). Rainfall
and temperature were examined over time to determine
whether either provides cues that birds might use to
indicate the breeding season.
The black-cheeked gnateater is relatively common and
is the only species in the family that is endemic toAtlantic
Forests, found from the northern coastal half of the state
of Santa Catarina in the south, almost to the state of Rio
Grande do Norte in the north, where suitable habitat
still remains (Ridgely & Tudor 1994, Sick 1997). Past
or present fragmentation of its Atlantic Forest habitat
has resulted in genetic divergence of local populations,
suggesting that this relatively sedentary species may
further suffer from continued deforestation (Lunardi
et al. 2008). As is typical of the family, this gnateater
is insectivorous and forages mostly on the ground (Alves
& Duarte 1996). The nest is a low platform built near
the ground on a horizontal palm leaf or branches and
the clutch size is invariably two eggs (Hillman & Hogan
2002, Hilty 1975, Sa´nchez & Aponte 2006, Willis et al.
1983). This species is sexually dimorphic: males have a
black mask and rufous cap that are lacking in the more
uniformly coloured females. Nests are cared for by both
sexes (Alves et al. 2002), as is typical of this and the sister
families Formicariidae and Thamnophilidae (Ridgely &
Tudor 1994).
Adult gnateaters were captured using mist-nets (2.5 ×
12 m, 30 mm mesh size) placed at convenient locations
anywhere inthestudyarea.Recordingsofgnateatersongs
were used to attract the birds to the nets (Lima & Roper
2009). When nets were placed near nests, they were
continuously monitored and removed immediately after
capture. Captured birds were uniquely colour-banded
and banded with permanent metal bands (provided
by CEMAVE, the Brazilian governmental branch that
oversees bird banding). Banding, measurement and
release of birds were all at the site of capture. Young
gnateaters were banded prior to fledging when possible.
Young birds were taken from the nest, measured,
uniquely colour-banded and returned to the nest several
days prior to fledging, to attempt to ensure that they did
not leave the nest prematurely.

Population dynamics of the black-cheeked gnateater 607
Nests searches and monitoring
From July 2006–April 2007, to find nests, adults were
followedwhen carrying nestingmaterial or while feeding
young and some nests were found when searching the
appropriate locations. Date and status (construction,
presence of eggs or young) were noted for all nests,
after which they were checked every 3–5 d. Nests
were monitored more frequently during egg laying and
hatching to allow better estimation of the associated time
intervals. Nests were observed from the greatest distance
possible to reduce possible observer influences.
Nest fate was determined by the evidence at the nest.
Successful nests were those that fledged young. Nest
failure due to predation was assumed if eggs disappeared
prior to hatching, or the young disappeared prior to
the minimum date possible for fledging and adults were
never found with fledged young. Other forms of nest
failure were noted when possible. Daily nest survival
rate was estimated using the program MARK (version
5.1, G. C. White, http://www.cnr.colostate.edu/∼
gwhite/mark/mark.html) (Dinsmore & Dinsmore 2007).
Survival of adults and young
To estimate survival, monthly censuses were carried
out from October 2006 to September 2007. During
these censuses, all territories were visited within an
interval of 1–2 d, pairs and young birds were located
and individuals with colour-bands were noted. Monthly
encounterswithmarked individualswereusedtoestimate
monthly survival ratesusing theprogramMARK(version
5.1), which were then converted to annual survival
rate.
Territory mapping
Territoriesweremappedbymodifyingamapof thereserve
that includes trails in and near the study area on which
reference points were established by a combination of
GPS reference points and triangulation. When marked
birds or nests were found, the distance and compass
angle to the nearest reference point was measured,
allowing the estimation of XY coordinates for each
sighting and nest. Territory size was estimated with
these XY coordinates and the program Kernelhr (Version
4.28 1998; Worton 1989), using fixed kernels and least
squares cross validation.
Population growth (r)
We wished to infer population trends in this study. Thus,
we used the values we estimated from nesting success,
adult and young survival, to estimate the population
growth rate, r, following Odum (2004) and Stahl & Oli
(2006). At its simplest (Odum 2004), r is calculated by
arrivals and departures of individuals in the population.
Thus, r = a – d. Arrivals, a, are merely calculated as
fledglings produced plus new individuals that appear in
the population through immigration. Departures, d, are
those individuals that disappear from the population (d =
1 – P; where P is survival rate). In practice, departures
may occur through mortality or emigration.
Toestimate r followingStahl&Oli (2006), the following
equation is used:
λ
α+1
− λ
α
·Pa − λ P
α−1
j F · +P
α−1
j PaF − P
α
j ·F = 0
wherePa isadult survival,α isageatmaturity inyears,Pj is
juvenile survival, F = mPj, where F is average fertility per
female, m is fecundity (fledglings per monitored female).
Substituting the appropriate values we arrive at λ, from
whichwemaycalculate r (asλ=er).Weexaminedseveral
values estimated from the data to better understand
population growth and stability and which parameters
should be most influential in population dynamics.
RESULTS
Pairs
Atotalof18gnateaterswerecaught(10males,8 females),
16 of which were captured prior to the end of October
2006. Only males were seen building nests based on six
observations of four pairs at four nests observed during
construction. Both adults carried out parental activities
(incubating, feeding young, removing faeces; n = 4 nests
of different pairs). Gnateaters are apparently permanently
monogamous although pair bonds may break. From July
to September, when any individual was encountered it
was invariably accompanied by the other member of the
pair (n = 39). From September to December, one or the
other individual of a pair was often found (n = 106)
when the other was occupied with nest care in some
way (incubating, feeding young, or otherwise near the
nest). Once fledging occurred, pairs were again found
foraging in pairs, sometimes with young birds from the
most recent nest (n = 8 observations of three pairs with
successful nests). After failed nesting attempts due to
predation (not inclement weather), one (n = 2, one male
and one female), or both (n = 1) members of the pair
disappeared fromtheir territorieswithnosignofpredation
of the adults at the nest. Since there was no evidence of
predation of the adult birds at nests, we interpret this
as territory and mate abandonment subsequent to nest
predation.

608 ANDRE´ MAGNANI XAVIER DE LIMA AND JAMES JOSEPH ROPER
Figure 2. Climate at Salto Morato Nature Reserve for 1 y, bracketed
aroundthestudyseasonandbeginningnear thesouthernwinter solstice
(21 June). On all graphs, the right ordinate axis is day-length (h) shown
as thedashed line:weekly total rainfall and smoothed rainfall (a),weekly
minimum (b) and weekly maximum temperatures (c). The first vertical
line indicates the date of the first nesting attempt while the second
vertical (dashed) line indicates the date of the last active nest.
Breeding season
Thefirstnestwas foundunderconstructionon12October
2006 and was probably the first nest of the year in the
study area because no other evidence (such as young
birds) was found that indicated any prior attempt by
any other pair. The last nest, found under construction
on 12 January 2007, was abandoned a few days later,
apparently prior to egg-laying. The last date of an active
nest was 20 January when the young fledged from the
nest. This interval, 12 October–20 January, is 100 d
(Figure 2).
If climate influences the breeding season, how it does
so is not obvious. There are no clear climatic trends
that might be associated with nesting, or precede nesting
and thus may act as a trigger (Figure 2). Both rainfall
and variation in rainfall increase during the beginning
of the breeding season (Figure 2a). Smoothed rainfall is
greater during the breeding season (mean = 66.6 mm
wk−1) than the non-breeding season (45.6 mm wk−1).
However, neither rainfall nor smoothed rainfall change
in any consistentway thatmight indicate a cue preceding
the onset of breeding (Figure 2a). Temperatures are
somewhatgreaterduringthebreedingperiodthanprior to
breeding (Figure 2b, c). Yet, only minimum temperature
is lower during the non-breeding season (13.9 ◦C) than
the breeding season (17.1 ◦C). High temperatures do not
differ between breeding and non-breeding seasons (both
means ∼ 32 ◦C). The only other climatic variable that is
always consistent is photoperiod.
Nest construction lasted14and20d in the twonests for
which the interval between initiation and egg laying was
observed. The interval between egg-laying and fledging
was 38, 41 and 44 d (n = 3 nests that were followed
for the entire interval). Two fledglings were seen more
than twice in their natal territory and the interval from
fledging to the last sighting was 65 d. At 40 d, coloration
of the youngwas already sexually dimorphic. By60d, the
plumage of the juvenile birds was very similar to that of
the adults (n = 2 marked juveniles from one nest).
Nest and reproductive success
Fifteennestswerewell-monitored,butpartial information
(including success) was available for 18 nests. Clutch size
was two in 17nests, one in the other. Of 10 pairs, one pair
attempted threenests, threepairsattempted twonestsand
six pairs nested only once. Also, all renesting occurred
after failed nesting attempts, and no pair successfully
nested more than once.
Nest survival rate was 0.966 d−1 (SE = 0.0115), with
4 successes in 18 attempts (22%, or 1:4.5 attempts).
Nine nests failed due to predation, four failed during
torrential rainsandonenestwasabandoned forunknown
reasons. Of the nests that were preyed on, six appeared
undisturbed. Total production of young was 0.36 per
adult, based on eight young of the 22 adults.
Adult and fledgling survival
Eight of the original 18 previously captured and marked
adults were seen in the area at the end of the study,
approximately 1 y after first capture, for an apparent
annual survival rate of 44% y−1. Adult survival based
on monthly observations during a 9-mo interval was
estimated using MARK at 0.945 mo−1 (SE = 0.024,
usingsine function, constant survival, constant recapture
probability).Weused the constant survival and recapture
as the most parsimonious and it was statistically similar
to the other possible models. Thus, over a 12-mo period
the annual survival rate would be 0.94512 = 0.505 y−1.
A total of eight nestlingswere banded just before fledging.
Of the eight young that were banded before fledging, six

Population dynamics of the black-cheeked gnateater 609
Table 1. Estimating population growth rate (λ) and the intrinsic rate of increase (r) following Stahl
& Oli (1996) with four possible combinations of adult (Pa is constant at 0.44 y−1), juvenile survival
(Pj),m (production rate of females per female) and fertility rate (F), followed by a hypothetical value
of adult and juvenile survival rates that would result in a stable population. Observed values all
suggest rapid population decline. For a stable population (λ ≈ 1, r ≈ 0), the last two rows illustrate
adult survival rates that would be required given the values of the other parameters.
Population state Survival m F λ r
Observed Pa = Pj 0.4 0.176 0.616 −0.485
Pj = 1/2 Pa 0.4 0.088 0.488 −0.717
Pa = Pj 0.3 0.132 0.572 −0.559
Pj = 1/2 Pa 0.3 0.036 0.475 −0.743
Stable 0.895 (Pj = 1/2 Pa) 0.4 0.179 0.993 −0.007
survived until they apparently left their natal territories
of their own volition (32, 33, 42, 44, 64 and 65
d after fledging), and the fate of the other two was
unknown.
Arrivals and departures from the population
A total of eight young were produced, 10 adults
disappeared from the population and six adults arrived
to take their place in the population. Thus, for the Odum
(2004)model a– d=16–8=4. For theStahl&Oli (2006)
model, adult survival, Pa = 0.44. Juvenile survival, Pj
was given two values: first, we assumed Pj = Pa because
apparently all young survived to become independent.
Second, Pj = 1/2 × Pa as an extreme lower estimate
following Ricklefs & Bloom (1977). Fecundity, m = 0.8
since10femalesweremonitoredandatotalofeightyoung
were produced. Average fertility, F = mPj = 0.8 × 0.44,
or0.8×0.22, forhigh (0.352)and low(0.176) estimates.
Thus, we combined the possible values of Pa, Pj and F to
estimate the range of likely values of r (Table 1).
Estimating r
WithN =0.36, I =0.16 and S (and also Pa,)=0.44, then
a = 0.52, d = 0.56 and r is approximately zero (0.52 –
0.56= –0.04). Alternatively, following Stahl & Oli
(2006):
λ
α+1
− λ
α
·Pa − P
α−1
j F ·λ + P
α−1
j F ·Pa − P
α
j ·F = 0
Which, in this one generation studyworks out to be, since
α = 1, then Pα−1j = 1 and the equation reduces to:
λ
α+1
− λ
α
·Pa − F ·λ + F ·Pa − Pαj ·F = 0
and if Pa = Pj, then the last two terms cancel out and the
equation is reduced to:
λ
α+1
− λ
α
·Pa − F ·λ = 0
Thus, with Pa = 0.44, Pj = Pa or 1/2 Pa, and m = 0.4
(apparent fledging success of female offspring) or m = 0.3
(apparent survival to independence of female offspring),
F = 0.176, 0.088, 0.132, 0.036 (Table 1). Population
growth (λ) ratewith these values varies fromamaximum
of 0.616 to a minimum of 0.475 (Table 1).
Population size and spatial distribution
A total of 18 adults (11 males, 7 females) and eight
nestlings were banded in 10 territories. During the study,
these individuals were sighted (recaptured) another 212
times (n = 14 for young birds, 144 for males, 61 for
females). One individual was encountered 25 times, nine
were encountered11 times and two individualswere only
seen at the time of capture.
Territory size was estimated for eight pairs based on
sighting coordinates. Sightings (10–38 per pair) were
temporally independent. Territory size was correlated
with the number of observations used in estimating size
(r=0.78, df=8, P<0.05). Controlling for the number of
observations with regression, territory size varied from
2.14–3.74 ha (SE = 0.166 ha). This gives a density
estimate of 0.27–0.47 pairs ha−1 (Figure 3).
Territories may not be permanent. All pairs that
attemptedmore thanoneattempt (n=4)did sowithin the
limits of their territory. Also, pairs that were in the area
when reproductionbegan in2007 (60%)were stillwithin
their territories of 2006, as well as individuals that lost
a partner from the previous year (n = 3). However, four
pairsabandoned their territories followingnest failuredue
to predation prior to the beginning of the 2007–2008
breeding season. Thus territories and pairs seem to be
stable when reproduction is successful.
DISCUSSION
Theblack-cheekedgnateater appears tohavea life history
atypical of tropical species. Relatively high reproductive
success, a short breeding season and low adult survival
are more typical of temperate birds (Karr et al. 1990,
Ricklefs 1969, Skutch 1985). While adult survival rate
was calculated at only 0.44 y−1 we suspect that this

610 ANDRE´ MAGNANI XAVIER DE LIMA AND JAMES JOSEPH ROPER
Figure 3.Map showing sighting locations of the nine different pairs (each
symbol indicates a different pair) and their nests during 2006–2007.
underestimates the true value, since it would imply a
very rapidly declining population. This low survival rate
suggests that territories may not be permanent and
that pairs may move to new territories following nest
failure. Thus, based on these data, the simple estimate
(Odum 2004) of r = −0.04 (λ = 0.961) suggests a
stable population. However, estimates following Stahl
& Oli (2006) suggest a rapidly declining population
(Table 1). Indeed, if these rates were correct, then the
population would quickly disappear. Yet, our personal
observations beginning in 2003 show that these birds are
consistently found in this area. Thus, we suspect that we
underestimate adult survival, perhaps due to emigration
following unsuccessful nesting attempts.
If we assume that the reproduction rate is a correct
estimate for this population, simple substitution in the
equations allows us to calculate the adult and juvenile
survival rates thatwould leadtoastablepopulation.Thus,
we see that if adult survival varies between 80–90% y−1,
and juvenile survival varies from half that of adults to the
same as adults, the population would be stable (Table 1).
We will return to this question below.
Breeding season
Understanding the proximate factors, or cues, that might
be associated with the initiation of breeding is complex at
this subtropical location. Determining whether climate
is important would require several years of breeding data
for the variation in the timing of breeding and that of
temperature or rainfall to show an association. At this
latitude, rainfall is quite variable throughout the year
and does not seem to provide a regular and predictable
stimulus that might initiate breeding. Temperature and
photoperiod are very strongly correlated and so either or
both might be important (Marques et al. 2004). During
this year of study, climate was quite variable, hence it is
difficult to identify cues for breeding. If food abundance is
important, thenpresumablyclimatemayplayaroledueto
its influence on insect abundance patterns (Wolda1992).
Day-length, shown to be important for some species
in the southern hemisphere (Sick 1997, Stutchbury &
Morton 2001), and the closely correlated temperature,
are the only climatic variables consistent and predictable
enough to be important for tropical species (Hau et al.
1998, Wikelski et al. 2000). Regardless, long-term or ex-
perimental data are necessary to tease apart the potential
cues for initiating and ending the breeding season.
Interestingly, breeding season length (about 100 d)
of the gnateater is somewhat shorter than most
insectivorous species of the region for which records
exist. For example, Elaenia chiriquensis (5 mo, Medeiros
& Marini 2007), Macropsalis forcipata (5 mo, Pichorim
2002), Augastes scutatus (6 mo, Costa & Rodrigues 2007)
and the commonly accepted 6 mo for Atlantic Forest
species (Maia-Gouveˆa et al.2005, Sick1997) are allmuch
longer than that of the gnateater. Some other tropical
species have similar breeding-season lengths (Cacicus
haemorrhous, 3.5 mo, Duca & Marini 2004, Lathrotriccus
euleri, 4 mo, Aguilar et al. 1999) as well as subtropical
species (Ricklefs & Bloom 1977).
Territoriality
Territory size for the gnateater varies around an average
of 2.94 ha, or 34 pairs per 100 ha. This is similar to
that of other, closely related, tropical species, such as the
thamnophilids or formicariids (Table 4 in Robinson et al.
2000a, b). While the family Conopophagidae is poorly
studied, the two other species forwhich data are available
had much larger territories. In the Brazilian Amazon, C.
aurita had large territories (mean ± SE = 6.25 ± 3.55,
or 16 pairs per 100 ha, Stouffer 2007), while in Peru,
C. peruviana had even larger territories, with only three
pairs per 100 ha (Terborgh et al. 1990). Here we found
nine territories in somewhat less than 25 ha and we
believe that this is typical of this region. While small, the
territory size of C. melanops is more similar to that of other
Atlantic Forest species, such as Thamnophilus caerulescens,
Dysithamnus mentalis and Pyriglena leucoptera (Duca et al.
2006) than to congeneric Amazonian species.
Monogamous and insectivorous, C. melanops is typical
of understorey insectivores in the tropics (Stutchbury
& Morton 2001). However, monogamy may not be
permanent, especially following nest predationwhen one
or both individuals in the pair apparently abandoned the

Population dynamics of the black-cheeked gnateater 611
territory. In one territory, soonafter abandonment by one
member of the pair, that individual was replaced. When
both members of the pair left the territory after nest pred-
ation, the territory remained unused for the remainder
of the breeding season. We suspect that this may be a
reproductive strategy in which, after nest predation, one
or both members seek new, perhaps better, territories.
If so, birds may gradually disappear and be counted as
deaths in capture–recapture studies. Therefore, assuming
territory permanence should be avoided.
Reproductive success and offspring survival
Highnest predation rates are common in tropical systems
(Martin 1995, Ricklefs 1969, Robinson et al. 2000a, b,
Roper 2005) and in Atlantic Forests (Duca & Marini
2005a). Thus, it is no surprise to find that predation
here is also the main cause of nest loss, although a
daily survival rate of 0.966 is relatively high. With 0.35
young produced per adult per year, it is unclear whether
reproduction is sufficient for the population to replace
itself. In comparison, the abundant E. chiriquensis in
centralBrazilhadarateof0.48youngpernest rather than
per adult (Medeiros & Marini 2007). Interestingly and
perhaps due to the short breeding season, persistence in
renestingwasapparentlynotauseful strategy for insuring
successful reproduction (Roper 2005).
Annual survival, adults and young
Survival rates for C. melanops are low, at 0.44 y−1. Adult
Vireo latimeri survival is 0.74 y−1 and juvenile 0.40 y−1
(Woodworth et al.1999). Survival rate for theneotropical
migrant Catharus ustulatus is 0.56 y−1 for adults and
0.25 y−1 for the first year birds (Gardali et al. 2003) and
0.50y−1 forWilsonia pusilla, anothermigrant (Chase et al.
1997). Survival rates in a variety of birds vary between
0.51–0.58 y−1 (based on mist-net captures, Karr et al.
1990). Greater survival rates were found in Catharus
frantzii in Mexico, averaging 79% y−1 (Rangel-Salazar
et al. 2008), In this study, due to the possible occasional
movement of pairs after failed territories, this low survival
ratemaybeanartefact.WhileKarr et al. (1990) estimated
relatively low survival rates for tropical birds, that study
was possibly biased due to the nature of the estimation
and the likelihood of dispersal, or even by effects like
body size or foraging guild (Brawn et al. 1995). Thus,
if this survival rate is underestimated, then estimates of
population growth rates will also be underestimated.
The nesting cycle is long in this species. From the
beginning of nest construction to fledging may take more
than 2 mo, with another 2 mo for post-fledging care. In
the western slaty antshrike (Thamnophilus atrinucha) the
nesting interval is much shorter, while post-fledging care
may be similar (Roper 2005). An important difference
is that in the antshrike, rapid renesting is possible and
so each breeding season may include multiple nesting
attempts, while in the gnateater, fewer nesting attempts
will be possible each season. Also, the breeding season
is longer in the antshrike. Thus, these results suggest
that some breeding parameters are underestimated in
the gnateater, or perhaps extended parental care is an
adaptive strategy to increase offspring survival (Russell
2000).
Population dynamics
Werecognize thatpopulationparameterestimatesmaybe
difficult to estimate with small sample sizes. Nonetheless,
with these data and in context, several hypotheses and
avenues for futurestudyare indicated.First,adult survival
rates (0.44 or 0.51 y−1) are low (Stahl & Oli 2006),
even by comparison with rates in Karr et al. (1990),
and we believe that they are underestimated. Second,
production of young does not replace those adults that
disappear in any given year. Yet, the population appears
to be more or less stable, despite the numbers. If stable,
then this implies that adult survival is underestimated
(and thus emigration is important). Perhaps this species,
and others in the genus Conopophaga, use a-species
strategy heretofore not observed in apparently territorial
neotropical birds in which unsuccessful territories are
abandoned. Subsequent absence from these territories
would appear as mortality in capture–resighting studies.
We suggest that short-term studies, such as this,
attempt to estimate population dynamic parameters.
From these analyses we can generate useful hypotheses
for future study and become more efficient and theory
driven in our data gathering. We show the difficulty
of discovering a causal link between climate and the
reproductive period at this location. Thus, searching
for that link over the short term will be unproductive.
Second, some tendencies may be suggested due to the
nature of these data. For example, when reproduction
rates are high, population growth rates aremost strongly
influencedbychanges inreproduction.Ontheotherhand,
when reproduction rates are low, population growth
rates are most influenced by survival (Sæther & Bakke
2000, Sæther et al. 2004, Sibly et al. 2005, Stahl
& Oli 2006). Therefore, once we recognize that adult
survival (and perhaps juvenile) was underestimated, we
must conclude that territories are not permanent. Thus,
greater effort should be spent in capture–recapture (or
capture–resighting) studies, since survival, rather than
reproduction, provides more information with which to
understand population dynamics. Similarly, in a long-
term study of the ruddy-capped nightingale thrush

612 ANDRE´ MAGNANI XAVIER DE LIMA AND JAMES JOSEPH ROPER
(Catharus frantzii), survival was also shown to be most
important in determining population dynamics (Rangel-
Salazar et al. 2008) Nesting should be followed as much
as possible, but more information (for understanding
population dynamics) will come from increasing the
number of individuals captured rather than the number
of nests found.
Thus, by using values derived even from somewhat
limited data, we have developed testable hypotheses
for future work. First, we suggest that climate per se
should not provide the proximate cues for the nesting
cycle in Conopophaga and that to better understand the
reproductive cycle researchers should look towards day
length as a cue. Next, by using nesting success and
adult survival data, we find an inconsistency that, if
correct, would suggest rapid population decline, which
is clearly not the case. Hence, survival and territory
dynamics, rather than reproduction, should be more
intensely studied. Therefore, short-termdatamay be used
toestimatepopulationparametersandcandirect research
to test specific hypotheses, by which further advances in
understanding population dynamics in tropical birds will
be more forthcoming.
ACKNOWLEDGEMENTS
Thanks to the very helpful field assistants: Flora H. de
Mello-Leita˜o and Arthur G. Nobre. Also, for the help
of the personnel of the Salto Morato Nature Reserve,
especially Paulo C. Chaves, Alan Y. Mocochinsky and
Bruno Xavier. Thanks to Cı´ntia Cornelius and Miguel
A. Marini for their constructive criticisms of earlier
versions of this manuscript. And, thanks to the Fundac¸a˜o
O Botica´rio de Protec¸a˜o a` Natureza for the financial support
as well as infrastructure in the field and CAPES for their
financial support. We thank Susan K. Willson and an
anonymous reviewer for their constructive suggestions
and observations.
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