DOI: 10.3897/zoologia.37.e46441

Authors: Paulo Vitor Alves Ribeiro, Camilla Queiroz Baesse, Márcia Cristina Cury, Celine de Melo

Abstract: Changes in the amounts and proportions of leukocytes, known as leucocyte profiles, have been documented for several bird species and have been used to measure stress levels in these animals. The present work ascertained the biological and ecological attributes that influence the leukocyte profile of Antilophia galeata (Lichtenstein, 1823), the helmeted manakin. This species has been deemed useful in ecological studies because it responds to environmental changes. Blood samples drawn from 89 individuals of A. galeata captured in a Cerrado forest fragment were subjected to analysis under optical microscopy to identify and quantify leukocytes and micronuclei. The number of lymphocytes was greater for males, non-reproductive individuals and individuals infected with ticks. None of the leukocyte components differed in relation to age, molting or body condition index. The amount of micronuclei was correlated with values for total leukocytes, H/L ratio, heterophils, basophils and monocytes. The results suggest that reproduction may be an immunosuppressive factor for the species, producing sexual differences in lymphocyte availability. In addition, biomarkers of genotoxic damage (micronuclei) were related to the amount of leukocytes, indicating that individuals may be sensitive to environmental disturbances. Leukocyte profiles can be considered a useful tool for addressing ecological questions that are relevant to the conservation of species in degraded environments.

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DOI: 10.3897/zoologia.37.e55615

Authors: Andrés Muñoz-Pedreros, Heraldo V. Norambuena, Claudia Gil, Jaime Rau

Abstract: Geranoaetus polyosoma (Quoy & Gaimard, 1824) is a diurnal raptor widely distributed in South America. Although the trophic ecology of this bird has been more studied in the southern extreme of its range, little information is available on its dietary response to prey supply in desert environments. In the present study, we report on the trophic ecology of G. polyosoma in a sub-urban desert zone in northern Chile, with the following objectives: (1) to quantitatively describe its diet and (2) to determine its dietary selectivity in response to prey supply in the study area. The diet of G. polyosoma consisted mainly of rodents (97.2%). A greater preference (p < 0.05) was observed for the following large prey items (> 19.5 g): two native rodent species, Phyllotis xanthopygus (Waterhouse, 1837) and Eligmodontia puerulus (Philippi, 1896); and two introduced rodent species: Rattus rattus (Linnaeus, 1769) and R. norvegicus (Berkenhout, 1769).

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DOI: 10.3897/zoologia.37.e37716

Authors: Leonardo Fernandes França, Victória Helen Figueiredo-Paixão, Thales Afonso Duarte-Silva, Kamila Barbosa dos Santos

Abstract: Rainfall in tropical semi-arid areas may act as a reliable cue for timing bird reproduction, since it precedes future food supply. With this in mind, we set-up a study to test the reproductive response of insectivorous bird to arthropod abundance and rainfall patterns. Sampling occurred in a seasonally dry Neotropical forest, in north-eastern Brazil, between October, 2015 and October 2016, at 14-day intervals. We used brood patch to assess reproductive periodicity of insectivorous birds (eight species, 475 captures, 121 patch records). We sampled arthropods to quantify abundance, using biomass and number of individuals (1755 individuals, 15 Orders). Rainfall temporal distribution was analyzed using daily precipitation data. We used a cross-correlation function to test for correlation and time-lags between the covariates under study. Both the number of reproductively-active birds and arthropod abundance were higher in time periods close to the rainy season. Increase in arthropod biomass in the aerial stratum preceded the period of greatest rainfall by one (14 days, r = 0.44) to three sampling periods (0.47). In contrast, the highest proportion of individuals with brood patches occurred after the main rainfall peak, with the strongest relationship occurring after two (0.52) to four (0.50) time lags. Finally, the proportion of individuals with brood patches was positively correlated with aerial stratum arthropod biomass when five time lags were considered (0.55). Our results support the hypothesis of a temporal process involving rainfall, arthropods and reproduction of insectivorous birds in the wet/dry tropics. However, rainfall did not appear to act as a cue for the timing of reproduction, since records indicated higher arthropod biomass before the main rainfall peak. At least occasionally in the study area, insectivorous bird reproduction peaks after food abundance.

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DOI: 10.3897/zoologia.37.e36026

Authors: Mariellen C. Costa, César A.B. Medolago, Amanda Murcia, Mercival R. Francisco

Abstract: The Chestnut-capped Blackbird, Chrysomus ruficapilus (Vieillot, 1819), is a common bird species in flooded areas of South America. Data on its reproductive parameters have been reported mainly for rice paddies from Uruguay and southern Brazil, where reproductive phenology might have been influenced by the chronology of agricultural activities. Here we provide reproductive data for a population in a natural marshland from São Paulo state, southeastern Brazil. A total of 45 active nests were monitored between December 2017 and April 2018. Clutch size was 2.8 ± 0.44. Incubation and nestling periods were respectively 11.8 ± 0.39, and 12.3 ± 0.75 days, and overall nesting success was 65%. The reproductive season lasted about five months, which is longer than that observed in rice paddies from southern Brazil. This suggests that the reproductive phenology has been underestimated before. Although clutch sizes were bigger in our study population than that from rice paddies from southern Brazil, nest survival was higher in the artificial habitat, suggesting that the Chestnut-capped Blackbird can obtain benefits from nesting in artificial habitats.

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DOI: 10.3897/zoologia.36.e32138

Authors: Cristiane Apolinario, Luis Fabio Silveira

Abstract: Cyanocorax chrysops (Vieillot, 1818) and Cyanocorax cyanopogon (Wied, 1821) are widespread jays. They are considered sister species according to recent molecular phylogenies. When analyzing museum specimens of both species, we found two individuals with intermediate plumage characteristics. They were collected near the range limits of both species, and we classified them as hybrids. Based on the sites where these specimens were found, we discuss the possible factors leading the interbreeding and compare our findings with information available in the literature. This is the first documented case of natural hybridization in jays in Brazil and the second case involving sister species within the New World jays.

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DOI: 10.3897/zoologia.36.e29719

Authors: Daniel Fernandes Perrella, Vitor Q. Piacentini, Paulo V.Q. Zima, Carlos Biagolini-Jr, Lais Ribeiro-Silva, Mercival R. Francisco

Abstract: Even though nest architecture has been useful for phylogenetic inferences among the Thamnophilidae (Aves: Passeriformes), the nests of only three out of five species of Myrmoderus (Ridgway, 1909) are known to science. Here we describe the nests, eggs, and nestling of the Squamate Antbird Myrmoderus squamosus (Pelzeln, 1868). Two nests were bulky bottom-supported cups, measuring 7.3 and 12 cm in maximum outside diameter, with a noticeably smaller egg cup, and they were placed within the crown of short, broad-leafed plants. Eggs were short-oval, with chalky white background color, and purple blotches and streaks more concentrated in the large end. One nestling was dark reddish grey, with bluish white feet, pinkish gray tarsi, and a blackish bill with bright yellow rictal flanges. In face of the great diversity of nest types found among the Thamnophilidae, we concluded that the nest of M. squamosus was similar to those of other congeners, giving support to this currently phylogenetically-defined genus.

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DOI: 10.3897/zoologia.36.e30475

Authors: Giulianne Sampaio Ferreira, Danilo Augusto Almeida dos Santos, Edson Varga Lopes

Abstract: The Amazon floodplains become periodically submerged as result of seasonal changes in the water levels throughout the year. These changes influence the availability of microhabitats and consequently the abundance of organisms in these ecosystems. In this study we investigated 1) how changes in the water level affect the richness and abundance of ardeid birds in the lowland floodplain lakes of the lower Amazon River, and 2) the microhabitats used by these birds throughout the seasonal cycle. Ten lakes were surveyed at each of the four phases of the seasonal cycle. In total, 3,280 individuals of 11 species were recorded. Of these, eight species occurred in the four phases, and three were observed in one or two phases. In the analysis including the entire family, there were more individuals in the phase with waters at lowest level and less in the phase that the water level was lowering. Many species were present throughout the seasonal cycle, suggesting that they might be resident species. However, their abundance varied throughut the cycle, suggesting that parts of their populations temporarily migrate elsewhere. The microhabitat that was most commonly used by most species at all phases of the seasonal cycle, with the excetions noted below, was “aquatic macrophytes", suggesting that ardeid birds have a strong preperence for this kind of habitat. Three species – Egretta caerulea (Linnaeus, 1758), Nycticorax nycticorax (Linnaeus, 1758) and Bubulcus ibis (Linnaeus, 1758) – preferred other microhabitats at some phase of their seasonal cycle. The present study shows that the floodplain lakes of the lower Amazon River are richer in ardeid bird species than other areas of the Amazon biome and other biomes in Brazil. The fact that we found rare species in our study and that they depend on aquatic macrophytes demonstrates the importance of conserving the floodplain lakes of the lower Amazon River.

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DOI: 10.3897/zoologia.36.e25717

Authors: Rodrigo Morais, Luiz Carlos Araújo, Gleidson Ramos Silva, Charles Duca

Abstract: This study describes aspects of the life history of the Tropical Mockingbird Mimus gilvus (Vieillot, 1808), including the breeding period, clutch size, nestlings and a list of plants used for nesting. Nests were monitored in an area of Restinga (sand-coastal plain) habitat in a protected area in southeastern Brazil. The data from 181 nests during five breeding seasons (2010-2014) showed that the Tropical Mockingbird has a long breeding season (26.1 ± 2.6 weeks) with up to two peaks of active nests from August to March. The breeding pairs made up to four nesting attempts in the same breeding season. The mean (± SD) clutch size was 2.4 ± 0.6 eggs (n = 169). The mean (± SD) incubation period was 14 ± 0.6 days, and the nestling remained in the nest for 14.5 ± 2.2 days. The nests were built on thirty plant species, and Protium icicariba (DC.) Marchand. was the plant species most commonly used for nesting. The breeding parameters of the Tropical Mockingbird are similar to those of other Mimidae species. The knowledge gained from this study makes the Tropical Mockingbird a good choice for future studies, particularly for testing ecological and evolutionary hypotheses regarding life history attributes, habitat selection and parental investment.

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DOI: 10.3897/zoologia.35.e14664

Authors: Carla Gheler-Costa, Fabio Henrique Comin, Letícia C. Gilli, Luciano M. Verdade

Abstract: Although the concept of optimal foraging has been extensively discussed, foraging efficiency is difficult to assess in vertebrates. In this study, we determined the foraging efficiency of the Brazilian cormorant, Nannopterum brasilianus Gmelin, 1789, by the direct, ad libitum observation of a group of four to thirteen individuals in an artificial pond at the University of São Paulo, Piracicaba, state of São Paulo, southeastern Brazil. Although this study was carried out in a highly anthropic environment, we can still conclude that the Brazilian cormorant is a relatively efficient browser and short-term diver. In anthropic environments, foraging success depends on the amount of time these birds spend diving, and stealing food is less common. Stealing occurs at relatively low rates but tends to be an efficient way to get food.

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DOI: 10.3897/zoologia.35.e14678

Authors: Laís Ribeiro-Silva, Daniel Fernandes Perrella, Carlos H. Biagolini-Jr, Paulo V.Q. Zima, Augusto J. Piratelli, Marcelo N. Schlindwein, Pedro M. Galetti-Jr, Mercival R. Francisco

Abstract: Identification of the predators of bird nests is essential to test ecological and evolutionary hypotheses and to make practical management decisions. A variety of nest monitoring devices have been proposed but many remain difficult to set up in the field. The aim of this study was to test camera traps as a potential tool to study predation of natural nests in a tropical rainforest environment. Specifically, we registered the predators, assessed their size range, and we compared the use of one and two cameras per nest. Of 122 nests from 24 bird species, 45 (37%) were depredated, and the cameras recorded the predator species in 29 of the total of depredated nests (64%). We identified predators in eight of 16 depredated nests (50%) in which we used one camera trap per nest, and we identified predators in 21 of 29 depredated nests (72%) when we used two camera traps per nest. The predators included six species of birds and six species of mammals, with body masses varying from 20 g to 16.5 kg. Causes for 10 of the 16 detection failures were identified and are discussed. These results suggest that camera traps are viable tools to investigate nest predation in a tropical rainforest area.

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DOI: 10.3897/zoologia.35.e13673

Authors: Daiane Ouvernay, Ildemar Ferreira, Juan J. Morrone

Abstract: Using track analysis and cladistic biogeography, we identified areas of endemism of hummingbirds in the Andean and Neotropical regions. Our results point out that the current areas of endemism of hummingbirds occur in the Andes, Guiana Shield, the Lesser Antilles, western Central and North America and the Chiapas Highlands. The cladistic biogeographic analysis suggests a hummingbird distribution shaped mainly by dispersal events.

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DOI: 10.3897/zoologia.35.e12993

Authors: Oscar Diego Evangelista-Vargas, Luis Fabio Silveira

Abstract: Penelope obscura Temminck, 1815 is a forest guan found in Brazil, Paraguay, Uruguay, Argentina and Bolivia. Three subspecies are currently recognized: Penelope o. obscura Temminck, 1815, P. o. bridgesi Gray, 1860, and P. o. bronzina Hellmayr, 1914. The limits between Penelope taxa are poorly understood since few studies have evaluated their differences in plumage, distribution and taxonomy. Based on 104 specimens deposited in ornithological collections we studied the variations in the plumage of P. obscura, including all characters that have been used to describe the included subspecies. Our results show that the plumage of these birds is extremely variable in southern and southeastern Brazil. Without any morphological and morphometric characters to support P. o. bronzina as a valid taxon, we synonymized it with P. obscura. Conversely, P. o. bridgesi, which occurs in the Yungas and the Chaco, is a distinct taxon and should be treated as a separate species from P. obscura.

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DOI: 10.3897/zoologia.35.e24569

Authors: Hermes Daros, William Barbosa Dutra, Charles Duca

Abstract: Existing knowledge of the breeding success and life history characteristics of most Neotropical bird species is scarce. Here, we help fill this gap by analyzing aspects of the breeding biology of the Tropical Kingbird Tyrannus melancholicus (Vieillot, 1819), which is a good model for this kind of study as it is a common species occurring in various environments, including urban areas, but little is known about its life history. We provide results concerning the breeding period, clutch size, incubation and nestling periods, description of nests, eggs and nestlings, and the plants used for nest sites by this species. Fifty-four nests were monitored over two seasons (2012–2014) in a protected area in southeastern Brazil. Nesting began at the end of the dry season and the beginning of the rainy season. The frequency of active nests varied according to variations in rainfall for each breeding season analyzed. The means and standard deviations of the incubation period (14.2 ± 1.9 days), nestling period (15.1 ± 0.8 days) and clutch size (2.5 ± 0.7 eggs) were similar to values reported for other Neotropical passerines. Twenty-one plant species used as nest trees and for the construction of the nests were identified. The results show that T. melancholicus is not highly selective when choosing plant species used for nest construction.

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DOI: 10.3897/zoologia.35.e12906

Authors: Anita Studer, Marcelo Cardoso de Sousa, Begoña Barcena Goyena

Abstract: 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. Mayfield (1975) showed a survival rate of 31.87% and MARK 24.09%. Hotelling’s T2 revealed no differences in nest characteristics between successful and failed nests (p-value > 0.05). Linear models showed that the size of the entrance of the cavity and its height from ground are the main nest characteristics influencing the nesting success of C. campanisona.

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DOI: 10.3897/zoologia.34.e20783

Authors: Luciane R. da Silva Mohr, Eduardo Périco, Vanda S. da Silva Fonseca, Alexsandro R. Mohr

Abstract: The Saffron-cowled Blackbird, Xanthopsar flavus (Gmelin, 1788), is a globally vulnerable icterid endemic to grasslands and open areas, and a priority species for research and conservation programs. This contribution provides information on the population size, habitat, behavior, breeding biology and nest success of X. flavus in two conservation units (CUs) in Viamão, state of Rio Grande do Sul, Brazil: the Environmental Protection Area Banhado Grande, and the Wildlife Refuge Banhado dos Pachecos, classified as an “Important Bird Area”. Searches for X. flavus were carried out mainly in open areas, the type of habitat favored by the species. Outside the breeding season individual behavior was recorded by the ad libitum method; during the breeding season, selected X. flavus pairs were observed following the sequence sampling method. The research areas were visited once a month, totaling approximately 530 hours of observations (September 2014 to June 2016) over 84 days, which included two breeding seasons. The species was observed across all months (not necessarily within the same year) and several X. flavus flocks were encountered, some with more than one hundred individuals (range = 2-137). Additionally, the behavior and feeding aspects, habitat use and breeding information on X. flavus were recorded. Two breeding colonies were found, and eleven nests were monitored. The estimated nesting success was 10% in Colony 1, but zero in Colony 2, where all eggs and nestlings were predated. Saffron-cowled Blackbirds were recorded in mixed flocks, mostly with Pseudoleistes guirahuro (Vieillot, 1819), P. virescens (Vieillot, 1819) and Xolmis dominicanus (Vieillot, 1823), the last also a globally endangered species. The collected information highlights the importance of CUs for the maintenance of X. flavus populations in the region. Maintenance of proper areas for feeding and breeding is necessary and urgent. Information from current research is being employed in the management plan of the Wildlife Refuge Banhado dos Pachecos in which X. flavus is one of the conservation target-species.

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DOI: 10.3897/zoologia.34.e19989

Authors: Daniel Fernandes Perrella, Paulo V. Davanço, Leonardo S. Oliveira, Livia M.S. Sousa, Mercival R. Francisco

Abstract: Despite the fact that E. chlorotica (Linnaeus, 1766) is common and widely distributed in South America, the reproductive aspects of the species are poorly documented. Here we present data on 18 active nests found from August to February, between 2007 and 2012. Nests were globular with a lateral entrance, and measured 97.9 ± 14.4 mm in outside height, 110.6 ± 11.6 mm in outside diameter, and were 4.88 ± 2.09 m above ground. They were often supported from bellow and were composed mainly of tiny dry leafs and leaflets, fine petioles, and plumed seeds, all compacted with spider web silk. Eggs were laid on consecutive days or with one day interval, and clutch size varied from 1–3 eggs (2.1 ± 0.6, n = 9 nests). Only females incubated the eggs, but both sexes were involved in nest construction and nestling attendance at similar rates. Incubation and nestling periods were 14 and 21 days, respectively, and overall nest survival probability was 5%. A vespiary used for nesting was not occupied by wasps and nest material was deposited only to form the incubatory chamber. Although nesting near wasps or bees is a widespread strategy among birds in general, nesting inside the nests of social insects is a poorly documented behavior.

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DOI: 10.3897/zoologia.34.e14882

Authors: Kei K. Suzuki, Tomoya Yoshida, Yutaka Yamane, Tatsuki Shimamoto, Ryuji G. Furukawa, Hisashi Yanagawa

Abstract: Describing the interactions among cavity breeders is key to understanding their breeding ecology. In this study the temporal difference in cavity use between the great tit, Parus major (Linnaeus, 1758) and the small Japanese field mice, Apodemus argenteus (Temminck, 1845) is investigated, as a first step for clarifying the interaction between bird and mammal cavity breeders. Forty-seven nest boxes were installed on tree trunks in two urban forests of Hokkaido Island, Japan, and the breeding nests of tits and mice were found in 34 and 11 boxes, respectively. The tits used the nest boxes throughout the breeding season, from May to July. In contrast, mice breeding nests were found in the last half of the breeding season, from July to October. Our results showed that field mice rarely used boxes during the tits’ breeding season. This study provides important information, such as temporal differences in breeding site use between tits and mice.

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DOI: 10.3897/zoologia.34.e13728

Authors: Vinicius R. Tonetti, Marco A. Rego, André C. De Luca, Pedro F. Develey, Fábio Schunck, Luís F. Silveira

Abstract: Stretching for more than 10,000 ha in the Metropolitan Area of São Paulo, southeastern Brazil, Serra da Cantareira comprises the largest native urban rainforest in the World, harboring a rich and diverse Atlantic Forest avifauna. Despite its closeness to major urban areas, few bird surveys have been conducted there. In this article we present an updated compilation of all bird species recorded for Serra da Cantareira, including personal records from the authors. A total of 326 species have been recorded for Serra da Cantareira since 1901; of these, nine have not been sighted there for the last two decades. The number of bird species endemic to the Atlantic Forest is high (80), and seven of its species are globally threatened. According to multivariate analyses the species diversity at Serra da Cantareira is similar to other regions of the Atlantic Forest, such as Carlos Botelho and Intervales state parks, where the vegetation is also ombrophilous dense forest. We discuss local changes in the avifaunal composition over the last decades and suggest the incorporation of large forest remnants to the Cantareira State Park to mitigate the impact of the northern section of Rodoanel Mário Covas, a highway (SP-21) that will soon be operational and will negatively impact the biodiversity of Serra da Cantareira.

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DOI: 10.3897/zoologia.34.e13729

Authors: Thaís Brisque, Lucas Andrei Campos-Silva, Augusto João Piratelli

Abstract: Bird-window collisions are a dramatic cause of bird mortality globally. In Latin America, statistics are generally very scarce and/or inaccessible so the frequency of such incidents is still poorly understood. Nevertheless, civilians have applied preventive methods (e.g. adhesive bird-of-prey decals) sparsely but, to our knowledge, no study has evaluated their effectiveness in Brazil. Here, we estimated the mortality rate of bird-window collisions and tested the effectiveness of bird-of-prey decals at preventing such accidents. We undertook daily searches for bird carcasses, presumably resulting from window collisions, near all buildings on a university campus over seven months. Adhesive bird-of-prey decals were then applied to the two buildings with the highest mortality rates and surveys continued for over 12 more months. The mortality rates before and after the application of decals and between seasons were then compared using Friedman test. We recorded 36 collisions, 29 around the two buildings with the highest collision rates 19 prior and 10 after our intervention with associated collision rates of 0.08 and 0.04 collisions/day. Although mortality was reduced by almost half, this difference was not statistically significant. The Blue-black grassquit, Volatinia jacarina (Linnaeus, 1766), and Ruddy ground dove, Columbina talpacoti (Temminck, 1810) suffered the highest number of collisions, followed by the Rufous-collared sparrow, Zonotrichia capensis (P. L. Statius Müller, 1776). Our bird-of-prey decals and efforts were insufficient to prevent or dramatically reduce the number of bird-window collisions. Therefore, we recommend that different interventions be used and additional long-term studies undertaken on their efficacy.

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DOI: 10.3897/zoologia.34.e13228

Authors: Lucas L. Lanna, Cristiano S. de Azevedo, Ricardo M. Claudino, Reisla Oliveira, Yasmine Antonini

Abstract: During flight, hummingbirds achieve the maximum aerobic metabolism rates within vertebrates. To meet such demands, these birds have to take in as much energy as possible, using strategies such as selecting the best food resources and adopting behaviors that allow the greatest energy gains. We tested whether hummingbirds choose sources that have higher sugar concentrations, and investigated their behaviors near and at food resources. The study was conducted at Atlantic forest remnant in Brazil, between June and December 2012. Four patches were provided with artificial feeders, containing sucrose solutions at concentrations of 5%, 15%, 25% and 35% weight/volume. Hummingbird behaviors were recorded using the ad libitum method with continuous recording of behaviors. The following species were observed: the Brazilian ruby Clytolaema rubricauda (Boddaert, 1783), Violet-capped woodnymph Thalurania glaucopis (Gmelin, 1788), Scale-throated hermit Phaethornis eurynome (Lesson, 1832), White-throated hummingbird Leucochloris albicollis (Vieillot, 1818), Versicoloured emerald Amazilia versicolor (Vieillot, 1818), Glittering-bellied emerald Chlorostilbon lucidus (Shaw, 1812) and other Phaethornis spp. C. rubricauda, P. eurynome and Phaethornis spp. visited the 35%-sucrose feeders more often, while the T. glaucopis visited the 25%-sucrose feeders more often. L. albicollis and A. versicolor visited more often solutions with sugar concentration of 15%. C. lucidus visited all patches equally. Three behavioral strategies were observed: 1) C. rubricauda and T. glaucopis exhibited interspecific and intraspecific dominance; 2) the remaining species exhibited subordinance to the dominant hummingbirds, and 3) P. eurynome and Phaethornis spp. adopted a hide-and-wait strategy to the dominant hummingbird species. The frequency of aggressive behaviors was correlated with the time the hummingbird spent feeding, and bird size. Our results showed that hummingbirds can adopt different strategies to enhance food acquisition; that more aggressive species feeding more than less aggressive species; and that the birds, especially if they were dominant species, visited high quality food resources more often.

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