Turdus Rufiventris Research Articles

Los parásitos como archivos secretos en las interacciones tróficas con sus hospederos: el caso del Zorzal Colorado

Helminths with heteroxenous cycles provide clues for the trophic relationships of definitive hosts, representing important sources of information for assessing niche overlap between males and females of non-dimorphic species. We necropsied 151 rufous bellied thrushes (Turdus rufiventris) captured in a metropolitan region in southern Brazil to analyze whether the structure of parasite communities is influenced by host sex or age. Most thrushes (93%) were parasitized by at least 1 species. The helminth community of Turdus rufiventris was composed of 15 species with prevalences from <1% to 60%. Although the prevalence of Conspicuum conspicuum, Microtetrameres pusilla and Aproctella stoddardi was higher in adults, Syngamus trachea was more prevalent in juveniles. Adults showed greater species richness of parasites than juveniles, probably as a consequence of an increase in the opportunities of infection with a larger set of parasites with aging. Adult males and females presented similar species richness of helminths and quite similar communities, allowing us to conclude that they prey upon the same invertebrates, including earthworms, snails, isopods, millipedes, cockroaches and grasshoppers. Therefore, trophic niche overlap between adult males and females is greater than between adults and juveniles.

Genotyping of Cryptosporidium spp. from free-living wild birds from Brazil

In wild and domestic birds, cryptosporidiosis is often associated with infections by Cryptosporidium galli, Cryptosporidium baileyi and Cryptosporidium meleagridis. In addition to these species, a number of avian Cryptosporidium species yet to be fully characterized are commonly found among exotic and wild avian isolates. The present study aimed to detect and identify samples of Cryptosporidium spp. from free-living wild birds, in order to contribute to the knowledge of the variability of this parasite in the free-living population of Brazil. Stool samples were collected from 242 birds, with the following proportions of individuals: 50 Emberizidae (20.7%), 112 Psittacidae (46.3%), 44 Cardinalidae (18.2%), 12 Turdidae (5.0%), eight Ramphastidae (3.3%), seven Icteridae (2.9%), three Estrilididae (1.2%), two Contigidae (0.8%), two Thraupidae (0.8%) and two Fringilidae (0.8%). Among the 242 fecal samples from wild birds, 16 (6.6%) were positive for the presence of oocysts of Cryptosporidium. Molecular characterization of the 16 samples of Cryptosporidium, were performed with phylogenetic reconstructions employing 292 positions of 18S rDNA. None of the samples of birds was characterized as C. meleagridis. C. galli was identified in one rufous-bellied thrush (Turdus rufiventris), five green-winged saltators (Saltator similis), one slate-coloured seedeater (Sporophila schistacea), one goldfinch (Carduelis carduelis) and three saffron finches (Sicalis flaveola). One goldfinch isolate, one buffy-fronted seedeater (Sporophila frontalis), one red-cowled cardinal (Paroaria dominicana) and one other saffron finch (S. flaveola) were identified as C. baileyi. Avian genotype II was found in an isolate from a white-eyed parakeet (Aratinga leucophthalma). Clinical symptoms of cryptosporidiosis in birds have already been described and the number of wild birds which were shedding parasites was high. Therefore, further epidemiological research and disease surveillance of birds in the wild is warranted.

Flexibility in Nest-Site Choice and Nesting Success of Turdus rufiventris (Turdidae) in a Montane Forest in Northwestern Argentina

We studied the consequences of nest-site choice on nesting success under differing disturbance levels for the Rufous-bellied Thrush (Turdus rufiventris). We compared nest-site choice and nest success between a disturbed site and an undisturbed site in a montane subtropical forest in northwestern Argentina. We found no overall difference in daily predation rate (DPR) between the disturbed and undisturbed sites. However, DPR of nests on bromeliads was significantly lower at the microhabitat level than on other types of subtrates at the disturbed site. T. rufiventris used bromeliads for nesting more often than expected by chance at the disturbed site. DPR did not differ between substrates at the undisturbed site and T. rufiventris used all substrates according to their availability. Nests had higher predation at the disturbed site when DPR on non-bromeliad substrates was compared between disturbed and undisturbed sites. Nest fate was independent of nest height. Our results suggest T. rufiventris' flexibility in nest-site choice, as reflected by increased use of the safest sites, i.e., bromeliads, in the disturbed site compared to the undisturbed site, may allow this species to survive in an otherwise much riskier habitat. Our results illustrate how microhabitat-scale effects can mediate landscape scale effects.

Bird-keeping in the Caatinga, NE Brazil

Brazil has one of the greatest bird diversities in the world, with around 1,800 species. However, many species are now threatened by illegal capture and trade that is largely driven by the culture of keeping wild birds as pets. This study documents the nature and purpose of bird capture and trade in the semi-arid Caatinga biome in northeastern Brazil, which has around 510 bird species and a population of around 25 million people. Data were obtained through observation in the homes of bird keepers and at open air markets, as well as through semi-structured and open-ended interviews and informal conversations with 52 wild bird keepers. We recorded 38 species of birds kept as pets in this study. The family with the largest number of species recorded was the Emberizidae (29%), followed by the Columbidae (16%) and the Psittacidae (16%). The most frequently kept species were: Paroaria dominicana, Aratinga cactorum, Icterus jamacaii, Sporophila albogularis, Turdus rufiventris and Cyanocompsa brissonii, which are all native to this region. Among the recorded species, only Pintassilgo (Carduelis yarrellii) is listed as an endangered species in Brazil. Of the people interviewed, 32% observed a reduction in abundance, or disappearance, of several bird species in the region. The need for measures aimed at the sustainability of wild avifauna use is therefore evident. These include law enforcement, commercial breeding and environmental education, of which the last is considered the most likely to be effective.

Linking frugivore activity to early recruitment of a bird dispersed tree, Eugenia umbelliflora (Myrtaceae) in the Atlantic rainforest

AbstractSeed dispersal by animals is a complex process involving several distinct stages: fruit removal by frugivores, seed delivery in different microhabitats, seed germination, seedling establishment, and adult recruitment. Nevertheless, studies conducted until now have provided scarce information concerning the sequence of stages in a plant's life cycle in its entirety. The main objective of this study was to evaluate the immediate consequences of frugivore activity for Eugenia umbelliflora (Myrtaceae) early recruitment by measuring the relative importance of each fruit‐eating bird species on the establishment of new seedlings in scrub and low restinga vegetation in the Atlantic rainforest, Brazil. We conducted focal tree observations on E. umbelliflora trees recording birds' feeding behaviour and post‐feeding movements. We also recorded the fate of dispersed seeds in scrub and low restinga vegetation. We recorded 17 bird species interacting with fruits in 55 h of observation. Only 30% of the handled fruits were successfully removed. From 108 post flight movements of exit from the fruiting trees, 30.6% were to scrub and 69.4% to low restinga forest. Proportion of seed germination was higher in low restinga than in the scrub vegetation. Incorporating the probabilities of seeds' removal, deposition, and germination in both sites, we found that the relative importance of each frugivorous bird as seed dispersers varies largely among species. Turdus amaurochalinus and Turdus rufiventris were the best dispersers, together representing almost 12% probability of seed germination following removal. Our results show the importance of assessing the overall consequence of seed dispersal within the framework of disperser effectiveness, providing a more comprehensive and realistic evaluation of the relative importance of different seed dispersers on plant population dynamics.

Frugivory and habitat use by thrushes (Turdus spp.) in a suburban area in south Brazil

Thrushes (Turdus spp., Turdidae) are among the most common frugivorous birds in urban areas around the world, where they disperse the seeds of a variety of plant species. We studied the abundance, habitat use, foraging behavior and diet of four thrush species (Turdus rufiventris, T. amaurochalinus, T. leucomelas, and T. albicollis) in a suburban area in south Brazil. Abundance, habitat use and foraging behavior were based on birds surveyed along a 3,240 m transect crossing open (formed by lawns, streets, and buildings) and forested areas. Diet was based on fecal samples collected from mist-netted birds. Turdus rufiventris was the most abundant species, followed by T. amaurochalinus, T. leucomelas, and T. albicollis. All species used forest fragments more frequently than expected by chance. A total of 91.8% (n = 147) of the fecal samples contained fruit remains, while 42.2% contained only animal matter. Most of the foraging records were on the ground, where birds got mainly invertebrates. Fruits and invertebrates were eaten more frequently in open than in forested areas. A total of 25 seed morfospecies were found in the droppings, including five exotic plant species. Thrushes overlapped widely in the fruit composition of their diets. The high abundance and degree of frugivory, coupled with the frequent use of forest patches, indicate that thrushes are among the great bird contributors to the seed dispersal occurring in urban forest patches, potentially influencing the vegetation dynamics of such habitats so important for the maintenance of the biodiversity in urban areas.

Comunidade de aves de sub-bosque em uma área de entorno do Parque Nacional do Itatiaia, Rio de Janeiro, Brasil

Este trabalho foi realizado em mata secundária no Município de Itatiaia, Estado do Rio de Janeiro (22º30'S e 44º30'W) próximo ao Parque Nacional do Itatiaia, com o objeitvo de descrever a comunidade de aves ali presente. Foram amostrados três tipos vegetacionais distintos: reflorestamento, bosque e pomar, tendo sido realizadas 19 excursões entre 1984 e 1999. As aves foram amostradas através de capturas com redes de neblina e anilhamento, tendo sido utilizadas de 15 a 31 redes de 12 x 2 m e malha 36 mm. Foram também obtidas medidas morfométricas (comprimento total, asa, bico, cauda e tarso) e dados biológicos (sexo, idade reprodução e muda). Depois de 5.621,79 horas-rede, foi registrado um total de 553 capturas, com 71 recapturas (12,84%); 417 indivíduos foram anilhados, e 65 beija-flores deixaram de ser marcados por falta de anilhas específicas. A comunidade estudada esteve representada por 77 espécies e 18 famílias, apresentando índice de diversidade H' = -1,594 e a curva do coletor com tendência à estabilização. As famílias com maior número de espécies foram Emberizidae (n = 21; 27,27%) e Tyrannidae (n = 15; 19,48%). As espécies com maior abundância relativa foram Turdus leucomelas (n = 40; 9,59%) e Turdus rufiventris (n = 36; 8,63%). Seis das espécies amostradas (7,8%) são endêmicas do bioma Mata Atlântica. Na estação chuvosa foram amostradas 68 espécies, e na estação seca, 42; e as capturas estiveram relacionadas com as chuvas (rs = -0,6778; p = 0,05). O período reprodutivo ocorreu de outubro a março estando correlacionado com o início da estação chuvosa (rs = -0,702; p = 0,052).

A Collection of Ticks (Ixodidae) from Wild Birds in Uruguay

Thirty nine wild birds from seven families (Alcedinidae, Emberizidae, Furnariidae, Parulidae, Trochilidae, Turdidae and Tyrannidae) were caught from 4 to 7 of February, 2004 at Rincón da Vassoura (31 degrees 15' S 56 degrees 03' W) Department of Tacuarembó, Uruguay. Ninety one nymphs and forty one larvae of Ixodidae were recovered from them. The majority of ticks were conventionally identified but 16S mitochondrial rDNA sequences were obtained for larvae and nymphs of Amblyomma with uncertain specific status to be compared with sequences of species from this genus. The 16S rDNA of Haemaphysalis juxtakochi Cooley was also obtained. Most ticks, 1 nymph of Amblyomma longirostre (Koch), 5 larvae of Amblyomma aureolatum (Pallas) and 3 nymphs of Amblyomma spp., 10 nymphs and 71 larvae of H. juxtakochi, 23 nymphs and 12 larvae of Ixodes pararicinus Keirans and Clifford, were found on the 5 Turdus albicollis Vieillot and 6 Turdus rufiventris Vieillot (Turdidae) caught. One nymph of A. longirostre and 2 nymphs of I. pararicinus were collected from the only Syndactyla rufosuperciliata (Lafresnaye) (Furnariidae) captured; 1 larva of I. pararicinus was collected on one of two Basileuterus leucoblepharus (Vieillot) (Parulidae) trapped and 1 nymph of A. longirostre was found on one of nine Elaenia parvirostris Pelzeln (Tyrannidae) captured. All these findings constitute new host records with the exception of I. pararicinus on S. rufosuperciliata, and stress the importance of Turdus as hosts for I. pararicinus, H. juxtakochi and A. aureolatum. Nymphs of H. juxtakochi and Amblyomma spp. were also found on man and vegetation.

Begging and short-term need in cowbird nestlings: how different are brood parasites?

Because brood parasitic nestlings are usually unrelated to their nestmates and to the provisioning adult, they are free from indirect costs of begging. Consequently, they are predicted to beg more intensely than host nestlings, and some models predict they will beg at an invariantly high level, regardless of short-term need. Previous work has shown intense begging by parasitic cowbirds, but short-term need was not controlled. In this study, we manipulated short-term need and measured begging intensity in two species pairs of host and parasitic nestlings: shiny cowbirds (Molothrus bonariensis) parasitizing larger hosts than themselves (rufous-bellied thrushes, Turdus rufiventris), and brown-headed cowbirds (M. ater) parasitizing smaller hosts than themselves (yellow warblers, Dendroica petechia). All four species increased their begging intensity with short-term need, though the change was much less pronounced between food-deprived and control treatments than between control and hand-feeding treatments. Shiny cowbirds begged more intensely than rufous-bellied thrushes following each treatment. In contrast, brown-headed cowbirds did not beg significantly more intensely than yellow warblers under any of the treatments. Intense begging by both species of parasites was as effective as host begging in stimulating the adults to make provisioning visits, but shiny cowbirds were less successful at acquiring food from adult thrushes. A wide array of factors may underlie the apparent differences in the begging behavior and success of brown-headed and shiny cowbirds, including relative size, experience, and local risk of nest predation. Our experiments clearly demonstrate, however, that these two species of parasitic cowbirds adjust their begging intensity based on short-term need.

A Comparative Study of Shiny Cowbird Parasitism of Two Large Hosts, the Chalk-Browed Mockingbird and the Rufous-Bellied Thrush

AbstractIt is usually accepted that generalist brood parasites should avoid using hosts larger than themselves because host chicks may outcompete parasite chicks for food. We studied the interactions between the Shiny Cowbird (Molothrus bonariensis) and two common hosts larger than the parasite, the Chalk-browed Mockingbird (Mimus saturninus) and the Rufous-bellied Thrush (Turdus rufiventris). For each host we determined (1) frequency and intensity of parasitism during the breeding season, (2) nesting success, egg survival, hatching success, and chick survival in unparasitized and parasitized nests, and (3) antiparasitic defenses. We also determined Shiny Cowbird egg survival, hatching success, and chick survival in both hosts. Parasitism reached 50% in mockingbirds and 66% in thrushes. In both species the main cost of parasitism was egg destruction through punctures. Hatching success, survival of host chicks, and nest survival did not differ between unparasitized and parasitized nests. Both hosts rejected parasitic white-morph eggs but accepted spotted-morph ones, even though they were significantly smaller than host eggs. The proportion of cowbirds fledged per egg laid in successful mockingbird and thrush nests was 0.4 and 0.6, respectively. Considering nest survival, reproductive success of Shiny Cowbirds was 0.15 in mockingbird nests and 0.17 in thrush nests. These values are similar to or higher than cowbird success with smaller hosts. Our results indicate that host quality is not only determined by host-parasite differences in body size, and that other factors, such as host defenses and nest survivorship, should be considered.Un Estudio Comparado del Parasitismo de Molothrus bonariensis en dos Hospedadores de Gran Tamaño, Mimus saturninus y Turdus rufiventrisResumen. Es aceptado generalmente que los parásitos de cría generalistas deberían evitar utilizar hospedadores de mayor tamaño corporal porque los pichones del hospedador podrían desplazar a sus pichones en la competencia por alimento. Se estudiaron las interacciones entre Molothrus bonariensis y dos hospedadores frecuentes de mayor tamaño que el parásito, Mimus saturninus y Turdus rufiventris. Para cada hospedador se determinó (1) frecuencia e intensidad de parasitismo durante la temporada reproductiva, (2) éxito de nidificación, supervivencia de huevos, éxito de eclosión y supervivencia de pichones en nidos no parasitados y parasitados, y (3) defensas antiparasitarias. También se determinó el éxito reproductivo del parásito en ambos hospedadores. El porcentaje de nidos parasitados fue 50% en Mimus saturninus y 66% en Turdus rufiventris. En ambas especies, el principal costo del parasitismo fue la destrucción de huevos por picaduras. El éxito de eclosión, la supervivencia de pichones y el éxito de nidificación fueron semejantes entre nidos no parasitados y parasitados. Ambos hospedadores rechazaron los huevos parásitos del morfo blanco pero aceptaron los del morfo manchado, si bien éstos fueron de menor tamaño que los del hospedador. La proporción de volantones de Molothrus bonariensis por huevo puesto en nidos exitosos de Mimus saturninus y Turdus rufiventris fue 0.4 y 0.6, respectivamente. Considerando la supervivencia de los nidos, el éxito reproductivo fue 0.15 en Mimus saturninus y 0.17 en Turdus rufiventris. Estos valores son similares o mayores que los reportados para hospedadores de menor tamaño que el parásito. Nuestros resultados indican que la calidad del hospedador no está sólo determinada por las diferencias en tamaño corporal entre el hospedador y el parásito y que otros factores, como defensas del hospedador y supervivencia de los nidos, deberían ser considerados.

A COMPARATIVE STUDY OF SHINY COWBIRD PARASITISM OF TWO LARGE HOSTS, THE CHALK-BROWED MOCKINGBIRD AND THE RUFOUS-BELLIED THRUSH

Abstract It is usually accepted that generalist brood parasites should avoid using hosts larger than themselves because host chicks may outcompete parasite chicks for food. We studied the interactions between the Shiny Cowbird (Molothrus bonariensis) and two common hosts larger than the parasite, the Chalk-browed Mockingbird (Mimus saturninus) and the Rufous-bellied Thrush (Turdus rufiventris). For each host we determined (1) frequency and intensity of parasitism during the breeding season, (2) nesting success, egg survival, hatching success, and chick survival in unparasitized and parasitized nests, and (3) antiparasitic defenses. We also determined Shiny Cowbird egg survival, hatching success, and chick survival in both hosts. Parasitism reached 50% in mockingbirds and 66% in thrushes. In both species the main cost of parasitism was egg destruction through punctures. Hatching success, survival of host chicks, and nest survival did not differ between unparasitized and parasitized nests. Both hosts reject...

Amblyomma aureolatum and Ixodes auritulus (Acari: Ixodidae) on birds in southern Brazil, with notes on their ecology.

Between January 1999 and December 2000, 876 bird specimens were captured in three different ecological environments from the Reinhard Maack Park, Curitiba, State of Paraná, southern Brazil. A total of 142 birds (16.2%) were infested with Amblyomma aureolatum (Pallas 1772) (N=699) and/or Ixodes auritulus Neumann, 1904 (N=18) ticks. Questing A. aureolatum nymphs (N=2) and adults (N=5) were also collected from the soil and the vegetation. None of the I. auritulus were collected off-host. We collected only immatures of A. aureolatum on birds, but all life stages of I. auritulus. The latter species was collected on Turdus rufiventris and on Synallaxis ruficapilla, which is herein recognized as a host of I. auritulus for the first time. Moreover, this is also the first report of A. aureolatum infesting birds, and 16 different bird species were found infested. It was observed that larval infestation was positively correlated with the dry and cold season, while nymphal infestation was positively correlated with the warm and rainy season. Although only 2-years worth of data is provided, our results suggest the infestation of birds by ticks was significantly higher at the biotopes formed by forest at its first stage of regeneration 'capoeira' and the original Araucaria forest habitat 'mata' than the ecotone between forest and urban areas 'peripheral area'.

Aves como potenciais dispersoras de sementes de Ocotea pulchella Mart. (Lauraceae) numa área de vegetação de cerrado do sudeste brasileiro

Embora os estudos de frugivoria e dispersao de sementes sejam importantes para a realizacao de planos de manejo e recuperacao de ambientes degradados, pouco tem sido pesquisado sobre o assunto no cerrado brasileiro. Neste trabalho sao apresentados aspectos da frugivoria e dispersao das sementes de Ocotea pulchella Mart. (Lauraceae) por aves. Treze especies de aves foram registradas consumindo os frutos de O. pulchella em 72 horas de observacao focal, entre os meses de agosto e outubro de 1999, numa area de cerrado da regiao central do estado de Sao Paulo (21o58' S, 47o52' W), Brasil. As principais especies potencialmente dispersoras foram o sabia-pardao, Turdus leucomelas (Muscicapidae), o sabia-docampo, Mimus saturninus (Mimidae), o bem-te-vi, Pitangus sulphuratus (Tyrannidae) e as guaracavas, Elaenia spp. (Tyrannidae). Nao foram encontradas variacoes significativas no numero de visitas nos diferentes intervalos de hora quando todas as especies foram analisadas em conjunto e quando cada especie foi analisada separadamente. Nao houve variacao significativa tambem no tempo de permanencia sobre as plantas entre as diferentes especies de aves. A taxa de consumo diferiu significativamente entre elas, tendo sido encontrada correlacao positiva significativa entre o peso das diferentes especies e o numero medio de frutos consumidos por visita. O tempo de permanencia sobre a planta e o numero de frutos consumidos foram positivamente correlacionados para Elaenia spp., para a maria-cavaleira, Myiarchus tyrannulus (Tyrannidae) e para o sabia-laranjeira, Turdus rufiventris (Muscicapidae). Embora especies primariamente frugivoras nao tenham sido observadas consumindo os frutos de O. pulchella, as especies oportunistas pareceram favorecer a eficiencia da dispersao, mantendo altas frequencias de visitas, altas taxas de consumo e permanecendo por curtos periodos de tempo sobre as plantas.

Bird Community of Inner La Plata City, Argentina

During the years 1991–2000,101 bird species were recorded in the city of La Plata, Argentina, 47 of which were breeding ones. The most abundant species were: Zenaida auriculata, Columba livia, Funarius rufus, Pitangus sulphuratus, Zonotrichia capensis and Passer domesticus. Columba maculosa, C. picazuro, Furnarius rufus, Turdus rufiventris and Molothrus bonariensis have increased in number, while Passer domesticus has decreased. Zonotrichia capensis may successfully compete for food with Passer domesticus. Sturnus vulgaris and Acridotheres cristatellus are new species in the breeding avifauna of La Plata city.

Low success of shiny cowbird chicks parasitizing rufous-bellied thrushes: chick–chick competition or parental discrimination?

The interaction between parasitic chicks and their hosts can have three outcomes: parasitic chicks might be favoured over the host young, disfavoured, or hosts might behave towards the parasitic chicks as towards their own young. I tested these hypotheses in a study of shiny cowbirds, Molothrus bonariensis, parasitizing rufous-bellied thrushes,Turdus rufiventris . Parasitic chicks were fed significantly less than the host young. I tested whether this was because parasitic chicks were outcompeted by the larger host young, or were disfavoured by the host adults. I videotaped parasitized broods containing a shiny cowbird raised with one host chick and nonparasitized broods containing a large and a small thrush that matched the size difference between the host and the parasitic chick. Parents used different rules for feeding chicks in the parasitized and nonparasitized nests. In nonparasitized nests, parents fed the chick that was positioned highest in the nest. However, in the parasitized nests, host chicks had a significantly greater chance of getting fed if they were higher or at the same height as the cowbird. When the cowbird chick was positioned higher than the thrush chicks, there was no difference between the chicks in the probabilities of their being fed. In addition, even when parents offered food to the cowbird chick, they then removed it from the cowbird's gape to feed their own chick as soon as it started begging. These results suggest that the poor success of shiny cowbird nestlings at nests of rufous-bellied thrushes is not simply due to competition with their larger nestmates, but may also involve parental discrimination. I discuss why hosts with chicks larger than the parasitic chicks may be more likely to evolve discrimination against parasitic chicks.

Seasonal Fluctuations of Birds, Fruits, and Flowers in a Subtropical Forest of Argentina

AbstractI quantified monthly variation in species composition and captures of birds in a premontane forest of northwestern Argentina. Seasonal patterns of frugivore-insectivores and nectarivores were compared with fruit and flower abundances, respectively. The composition of the entire bird community fluctuated seasonally; frugivore-insectivores showed a peak in captures during the wet season, insectivores peaked at the end of the dry season, and nectarivores peaked during the dry season. At a local scale (∼50 ha), captures of frugivore-insectivores were not correlated with number of plant species with ripe fruits for any vegetation stratum considered, but were correlated with a fruit phenology index that considers crop size. At a plot scale (∼7.5 ha), only understory flower abundance and captures of nectarivores were correlated, but only in the plot where both were more abundant. At a net-site scale (50 m2), captures of the Rufous-bellied Thrush (Turdus rufiventris) were correlated with understory fruit abundance, but only in the plot where fruits were more abundant. These results suggest that seasonal fluctuations in birds may be driven to some extent by their food resources. Premontane forest provides habitat for many migrants and also presumably acts as a source of birds that emigrate to disturbed areas. Although premontane forests should be a conservation priority for the region, they are poorly protected and suffering high deforestation.

SEASONAL FLUCTUATIONS OF BIRDS, FRUITS, AND FLOWERS IN A SUBTROPICAL FOREST OF ARGENTINA1

Abstract I quantified monthly variation in species composition and captures of birds in a premontane forest of northwestern Argentina. Seasonal patterns of frugivore-insectivores and nectarivores were compared with fruit and flower abundances, respectively. The composition of the entire bird community fluctuated seasonally; frugivore-insectivores showed a peak in captures during the wet season, insectivores peaked at the end of the dry season, and nectarivores peaked during the dry season. At a local scale (∼50 ha), captures of frugivore-insectivores were not correlated with number of plant species with ripe fruits for any vegetation stratum considered, but were correlated with a fruit phenology index that considers crop size. At a plot scale (∼7.5 ha), only understory flower abundance and captures of nectarivores were correlated, but only in the plot where both were more abundant. At a net-site scale (50 m2), captures of the Rufous-bellied Thrush (Turdus rufiventris) were correlated with understory fruit...

Using Shannon Entropy on Measuring the Individual Variability in the Rufous-bellied Thrush Turdus rufiventris Vocal Communication

We applied the information theory concepts to notes repertoire characteristics combined with temporal parameters of the Rufous-bellied thrush Turdus rufiventris song, using this particular case to test a new method of analysing quantitatively complex animal communication systems. Like most Turdus thrushes, Rufous-bellied thrushes are remarkable for their long, varied and melodious songs. For the analysis of the species repertoire, we used recordings of 44 individuals from 24 localities covering its full geographical range. We measured the repertoire size, note duration and rhythm (frequency of note utterance), and combined these parameters with the Shannon entropy values calculated for each individual. Although individuals maintain species-specific recognition capacity, we find a large variation between their song parameters and show that the information theory can be useful to analyse large and varied animal vocal repertoires. We are introducing two new parameters, temporal average entropy (Et) and utterance frequency average entropy (Ef), for measuring such communication systems.

Parasitism by Shiny Cowbirds of Rufous-Bellied Thrushes

I studied the interaction between a brood parasite, the Shiny Cowbird (Molothrus bonariensis), and a large host, the Rufous-bellied Thrush (Turdus rufiventris), in the Pampas Region of Argentina. Shiny Cowbird eggs were observed in 34 out of 70 (48.6%) thrush nests throughout the host's breeding season. The main damage inflicted by Shiny Cowbirds was the puncture of host eggs, which occurred in 55.9% of the parasitized nests and significantly reduced the host clutch size. Because of the host's short incubation period, cowbird eggs did not hatch more than one day before the host young. This small advantage of earlier hatching was not enough to outweigh the large size difference between the parasitic chicks and the host young. In 68.7% of experimentally-created broods containing one host and one cowbird chick, the cowbird chicks died of starvation. I conclude that the Rufous-bellied Thrush is a particularly poor host for Shiny Cowbirds because of its large size and short incubation period. The high rate of parasitism, even of such a poor host, indicates little selectivity by Shiny Cowbird females.

Toucans and thrushes as potential dispersers of seed-predatory weevil larvae in southeastern Brazil

Only recently have the interrelationships between seed-predatory insects and frugivores (seed dispersers) been considered of interest for evolutionary studies. Within the framework of "evolutionary triads," insect dispersion by frugivores that eat insect-infested fruits has been predicted. Such dispersal requires that insects survive passage through frugivore stomachs. In this paper we document this in the case of a weevil (Revena rubiginosa) infesting the nut of a palm tree (Syagrus romanzoffiana) and an unidentified weevil infesting the seed of a tree belonging to the genus Eugenia (Myrtaceae). The fruits of both trees are eaten by toucans (Ramphastos dicolorus and R. vitellinus) and those of the palm also by thrushes (Turdus rufiventris).