Research Article |
Corresponding author: Anita Studer ( studer.anita@gmail.com ) Academic editor: Luis Fabio Silveira
© 2018 Anita Studer, Marcelo Cardoso de Sousa, Begoña Barcena Goyena.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Studer A, Cardoso de Sousa M, Barcena Goyena B (2018) Breeding biology and nest success of Short-tailed Antthrush Chamaeza campanisona (Aves: Formicariidae) in the Atlantic rainforest of northeastern Brazil. Zoologia 35: 1-8. https://doi.org/10.3897/zoologia.35.e12906
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We present the results of a 26-year study on the breeding biology of the Short-tailed Antthrush, Chamaeza campanisona (Lichtenstein, 1823) in an Atlantic rainforest remnant of northeastern Brazil (Alagoas/Pernambuco). We followed the fate of 38 nests, of which 19 failed, 11 succeeded and 8 had an unknown fate. The presence of most nests coincided with the beginning of the rainy season in March/April but nests with eggs and/or chicks were found throughout the year, with no records only in January. Nests were placed inside natural tree cavities that result from broken branches and trunks. Both parents were engaged in feeding the chicks, their diet consisted mainly of insects, spiders, and some unidentified berries. All nests had a clutch size of two eggs. Incubation took 19 days and the mean nestling period was 20.75 days.
Breeding season, breeding success, cavity-nesting, nest characteristics, Mayfield, linear model
Four species of Chamaeza Vigors, 1825 antthrushes have been recorded from forested habitats in Brazil (
Information about the breeding biology of C. campanisona is scarce (
We present our results on the breeding biology and nest characteristics of C. antthrushes, collected over a time span of 30 years in a forest known as Pedra Talhada. We also present the results of the nest success of this species and the relationship between nest characteristics and nest fate.
Observations on the bird C. campanisona were conducted at Pedra Talhada forest (09°14.00’S; 36°25.00’W), located 90 km from the Atlantic coast, on the border between the states of Alagoas and Pernambuco, northeastern Brazil (Fig.
Pedra Talhada forest is an Atlantic rainforest biome enclave and is considered as a submontane and montane semi-evergreen seasonal forest, regionally called “brejo de altitude”, far more humid than the surrounding lowland areas. These favorable climatic conditions are a consequence of the Borborema Plateau, which sweeps the oceanic winds and captures, by condensation, the humidity of the air that returns in form of rainfall. It is believed that, due to their particular climate, the altitude forest enclaves of the Brazilian Northeast can cope with the dry season (
The vegetation of Pedra Talhada forest includes rupicolous forests, slope forests and plain forests with sempervirens and deciduous trees up to 35 m high, as well as open vegetation areas such as rocky outcrops, clearings and marshes (
We observed the nests of C. campanisona birds for 30-years from April 1986 to April 2016, with the exception of 2010–2013, totaling 26 years of fieldwork. Nest search was carried out on an irregular day-schedule from one to four times a month, throughout each year. The nests were located either by observing conspicuous adult behavior (
Several parameters of the cavity and nest were recorded. We measured the height from the ground (FG) to the entrance of the cavity, and the following cavity dimensions: diameter of entrance, total size (width x height), and depth from the entrance to the nest located at the bottom of the cavity. We measured the height FG, diameter and weight of the nest.
We also identified the host tree species. Other variables such as egg dimensions, clutch size, breeding season and reproductive success were also documented. Egg shape was determined as suggested by
A nest was considered successful when at least one nestling fledged, and nest success was calculated using two different approaches: the
The nest-survival model in the MARK program is based on five assumptions for each nest: 1) the age of the nests were correctly estimated when they were discovered; 2) the fate of the nests were correctly determined; 3) discovering and checking the nests did not influence survival; 4) nest fates are independent; 5) daily nest-survival rates are homogenous (
Both the incubation (19 days) and nestling (20.75 days) periods were determined for C. campanisona during the study. This helped us to correctly determine the nest age for the model in the MARK program (assumption 1). When we encountered nests with eggs already being incubated, we determined the age of the nest by back-aging the mean incubation period from the hatching date. For example if a nest hatched 5 days after discovery, it meant it was 14 days old when we first encountered it. When nests were found during the nestling stage, we back-aged the mean breeding period from the fledging date. In the remaining cases, when nests were unsuccessful before hatching, we estimated the date when incubation began using the following equation: First day of incubation = date found – (incubation period – number of days observed/2) (equation C,
Nests with unknown fate were not included in the analysis with the MARK program.
Nest characteristics (cavity entrance height FG, nest height FG, cavity entrance size and cavity depth) were compared with the multivariate Hotelling’s T2 test to determine whether successful and failed nests were structurally different. Afterwards, we conducted univariate comparisons (t-tests) in order to detect which nest characteristics were remarkably different between successful and failed nests. Bonferroni corrections were applied to prevent type I error.
Finally, assuming that the daily survival rate (DSR) remains constant throughout the year, we investigated the effects of the above-mentioned nest characteristics on nest fate. We created a set of linear models combining the different explanatory variables and a stepwise model selection was carried out by calculating Akaike’s information criterion (AIC). ΔAICi and AIC weight were taken into account for model selection (
A total of 38 nests were observed in Pedra Talhada between 1986 and 2016. All nests were found in the more conserved patches of the forest, in places where the ground was covered by a thick layer of foliage and tree trunks were rather spaced apart (Fig.
Chamaeza campanisona is a non-excavator bird. Consistent with that, all nests observed by us were located inside natural tree cavities resulting from broken branches or trunks (Fig.
In some cases, we observed that certain cavities had been reoccupied for a subsequent breeding attempt. For example, the cavity of nest #2 in Psidium guineense tree was reoccupied four years later (nest #9); the cavity of nest 3, in a Byrsonima sericea tree, was reoccupied three years later (nest #7) and the cavity of nest #13 also in Byrsonima sericea tree was reoccupied six months later (nest #15). We were not able to verify if the same breeding pair had reoccupied the cavities.
Birds flew to the entrance of the cavity and stepped down to reach the nest that was placed at the bottom of it. Cavity entrance size was on average 144.95 cm2 ± 20.54 Standard Error (SE, extremes 48–360 cm2). Cavity entrances were placed at an average height from ground of 235.08 cm ± 16.48 SE (extremes 80–436 cm) and nests were located at an average height from ground of 134.89 cm ± 15.19 SE (extremes 15–380 cm). Cavity depth was on average 93.87 cm ± 6.18 SE (extremes 25–190 cm; Suppl. material
Eggs are white and short-oval according to
When hatched, the nestlings were fully covered with fine grey-violet down feathers and squeezed together forming a dark sphere, so that one could only distinguish the different parts of the bodies when handling the chicks. The bill was light purple with white flanges. The throat was slightly pink with greenish nuances; tibias, tarsus and digits were light violet with tiny white nails. When leaving the nest, even though it had a greenish-brown tone, the fledgling resembled the final adult plumage.
The incubation period lasted 19 days (n = 2) and the nestling period averaged 20.75 days ± 0.49 SE: 19 days (n = 2); 20 days (n = 1); 21 days (n = 3); 22 days (n = 1); 23 days (n = 1). Therefore, we estimated that the total breeding period lasted 39.75 days ± 0.49 SE.
Both parents participated in raising the chicks and their food consisted mostly of insects (crickets, grasshoppers, praying mantis, beetles, ants and caterpillars), several spider species and some unidentified berries. Even though we observed the parents bringing ants to the nest, we rarely saw them following army ants.
When approaching the nest, the adults zigzagged across the floor. Often one or both parents walked around the trunk before reaching the entrance of the cavity with a short flight and usually stopped there for a moment, looking at the surroundings before descending into the nest. The adults came in and out of the nests by climbing the interior walls. In some nests, we noticed that the walls became smooth from the many comings and goings of the birds. After feeding the chicks, the adults usually stopped again for a few seconds at the entrance of the cavity looking in all directions before flying away in a horizontal line. Sometimes the adult flapped its wings two to three times at the nest entrance before flying away. We were not able to determine the reason for this behavior.
During several morning observations of five nests for periods of five hours between 06:30 to 11:30 am, we observed parent-offspring feeding behavior. Our results show that parents fed 5–10 day old chicks 1–2 times/hour. Chicks that were 10 days old or older were fed less frequently (0.5–1 time/hour) and adults brought a greater quantity of food in each visit. In many cases, wings and legs of insects dangled from the parents’ beak (Fig.
The breeding periods were very irregular from one year to another and no nests were found in 2000 and 2001. The presence of most nests coincided with the beginning of the rainy season and most active nests with eggs or young were discovered between March and June, mainly in April, right before the rainy season reaches its peak (Fig.
To calculate the duration of the breeding season all data was pooled together (1986–2016). The first nest was found during incubation on February 17 and the last nest succeeded on December 28, representing a period of 315 days.
Out of the 38 nests, 19 failed, 11 were successful and eight had an unknown fate (Suppl. material
We observed that predators usually arrived at night. However, in most cases, the predation timing could not be determined and therefore no general patterns were identified. In two cases we discovered a White-eared opossum, Didelphis albiventris (Lund, 1840), sleeping in the nest, probably after consuming the eggs which had disappeared the same morning (February 1997).
Following the
Hotelling’s T2 test revealed no differences between successful and failed nests (T2 = 1.8952, p-value: 0.1552). Successful nests appeared to have greater cavity entrance heights FG, deeper cavities, greater nest heights FG and smaller cavity entrances, although based on individual tests these differences were not statistical significant (Table
t-tests between successful and failed nests (mean ± SE), n: number of observations (successful, failed).
Nest variable | n | Successful | Failed | t-test | df | p-value | p-value |
---|---|---|---|---|---|---|---|
EH (cm) | 38 (11, 19) | 301.18 ± 31.31 | 228.98 ± 21.69 | 1.90 | 19.420 | 0.0729 | 0.2916 |
NH (cm) | 38 (11, 19) | 188.64 ± 34.33 | 130.31 ± 18.88 | 1.49 | 16.150 | 0.1559 | 0.6236 |
D (cm) | 38 (11, 19) | 112.55 ± 12.59 | 86.00 ± 8.20 | 1.77 | 18.430 | 0.0938 | 0.3752 |
ES (cm) | 21 (9, 12) | 118.22 ± 19.53 | 178.25 ± 34.07 | -0.62 | 13.298 | 0.5460 | 1.0000 |
Of all candidate models, the model including cavity entrance height and cavity entrance size had the highest explanatory power (Table
Modela | df | p-value | Log-likelihood | AICc | ΔAICi | AICi Weight |
F~EH+ES | 4 | 0.0140 | -15.93 | 41.5 | 0.00 | 0.569 |
F~EH+D+ES | 5 | 0.0204 | -15.12 | 42.7 | 1.27 | 0.302 |
INTERCEPT | 2 | 0.0000 | -20.67 | 45.8 | 4.32 | 0.066 |
F~EH+NH+D+ES | 6 | 0.0471 | -15.10 | 45.9 | 4.39 | 0.063 |
Clutch sizes of three eggs were found by
The eggs of C. campanisona are white, consistent with the color of the eggs of most cavity-nesting birds (
The nest characteristics described here resemble in many ways the descriptions from previous studies of C. campanisona (
Bird breeding seasons vary considerably throughout the different regions of Brazil. It is generally acknowledged that birds depend on food availability to raise their young, which in turn depends on beginning of rainfalls, resulting on larger quantities of food (
The northeastern region has been qualified as one of the most irregular and semiarid regions worldwide (
In other areas within the distribution range of C. campanisona the breeding period of this bird is not as long. One of the few long-term studies published on this subject (
This long-term study of the Short-tailed Antthrush allowed us to evaluate the breeding success of C. campanisona in Pedra Talhada using two different methods. Analyses in the MARK program required that nest fate was known (
According to our analyses, nest success can be predicted by the size of the entrance of the nets’ cavity and height of cavity entrance from the ground. It has been largely established that nest failure due to predation or harsh climatic conditions is closely related to nest location, height, structure, shape and environment (
However, C. campanisona birds may not always be able to choose their cavities due to limited availability (
Predation is usually the primary source of nest mortality for both open- and cavity-nesting birds (
Chamaeza campanisona birds appear to depend on well-preserved forests with old, decaying trees for hosting the bird’s offspring (
We thank Luís Fábio Silveira for his valuable advice in reviewing our paper. We also thank Foundation Nordesta Reforestation & Education for supporting our field work and IBAMA/ICMBio institutes for cooperating with conservation measures. We are thankful to Felino Pedro Celestino, Luis Batista de Freitas and Manoel Nunes de Farias for their long-term assistance and collaboration in locating the nests. We thank Rodolphe Spichiger and Louis Nusbaumer for taxonomic identifications of trees and are grateful to Nicolas Spitznagel for his illustrating work.
Nests of Chamaeza campanisona found during the study period (1986–2016) with their respective characteristics
Data type: species data
Explanation note: Date of encounter could be of nests either with eggs (e) or with nestlings (n). Fate is given as: (F) failed, (S) successful, and (U) unknown. Exposure days refer to the observation period of each nest according to