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Northern Brazil (northern + brazil)
Selected AbstractsArchaeological mounds in Marajó Island in northern Brazil: A geological perspective integrating remote sensing and sedimentologyGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 1 2009Dilce de Fátima Rossetti Earthen mounds with archaeological artifacts have been well known in Marajó Island since the 19th century. Their documented dimensions are impressive, e.g., up to 20 m high, and with areas as large as 90 ha. The mounds, locally known as tesos, impose a significant relief on the very low-lying landscape of this region, which averages 4 to 6m above present sea level. These features have been traditionally interpreted as artificial constructions of the Marajoara culture, designed for defense, cemetery purposes, or escape from flooding. Here, we provide sedimentological and geomorphological data that suggest an alternative origin for these structures that is more consistent with their monumental sizes. Rather than artificial, the Marajoara tesos seem to consist of natural morphological features related to late Pleistocene and Holocene fluvial, and possibly tidal-influenced, paleochannels and paleobars that became abandoned as depositional conditions changed through time. Although utilized and modified by the Marajoara since at least 2000 years ago, these earthen mounds contain a significant non-anthropogenically modified sedimentary substratum. Therefore, the large Marajoara tesos are not entirely artificial. Ancient Marajoara cultures took advantage of these natural, preexisting elevated surfaces to base their communities and develop their activities, locally increasing the sizes of these fluvial landforms. This alternative interpretation suggests less cumulative labor investment in the construction of the mounds and might have significant implications for reconstructing the organization of the Marajoara culture. © 2009 Wiley Periodicals, Inc. [source] Two-step vegetation response to enhanced precipitation in Northeast Brazil during Heinrich event 1GLOBAL CHANGE BIOLOGY, Issue 6 2010LYDIE M. DUPONT Abstract High resolution palynological and geochemical data of sediment core GeoB 3910-2 (located offshore Northeast Brazil) spanning the period between 19 600 and 14 500 calibrated year bp (19.6,14.5 ka) show a land-cover change in the catchment area of local rivers in two steps related to changes in precipitation associated with Heinrich Event 1 (H1 stadial). At the end of the last glacial maximum, the landscape in semi-arid Northeast Brazil was dominated by a very dry type of caatinga vegetation, mainly composed of grasslands with some herbs and shrubs. After 18 ka, considerably more humid conditions are suggested by changes in the vegetation and by Corg and C/N data indicative of fluvial erosion. The caatinga became wetter and along lakes and rivers, sedges and gallery forest expanded. The most humid period was recorded between 16.5 and 15 ka, when humid gallery (and floodplain) forest and even small patches of mountainous Atlantic rain forest occurred together with dry forest, the latter being considered as a rather lush type of caatinga vegetation. During this humid phase erosion decreased as less lithogenic material and more organic terrestrial material were deposited on the continental slope of northern Brazil. After 15 ka arid conditions returned. During the humid second phase of the H1 stadial, a rich variety of landscapes existed in Northeast Brazil and during the drier periods small pockets of forest could probably survive in favorable spots, which would have increased the resilience of the forest to climate change. [source] Breeding biology of White-rumped Tanagers in central BrazilJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2010Luane R. Dos Santos ABSTRACT White-rumped Tanagers (Cypsnagra hirundinacea) are widely distributed in northern Brazil, Bolivia, and Paraguay, and are classified as vulnerable in the state of Paraná and as endangered in the state of São Paulo, Brazil. Little is currently known about their breeding biology. We studied the breeding behavior of White-rumped Tanagers in the Cerrado (Neotropical savanna) in central Brazil from 2002 to 2007. The breeding period extended from mid-August to mid-December. Nests were cup-shaped and located mainly in trees of the genus Kielmeyera at a mean height of 3.7 ± 0.3 m (SE). Clutch sizes varied from one to three eggs and the incubation period lasted an average of 16.0 ± 0.3 d. Incubation was by females only and started with the laying of the first egg. Mean nest attentiveness (percent time on nests by females) was 64 ± 0.08%. Nestlings were fed by males, females, and, when present, helpers. The mean rate of food delivery rate to nests was 5.2 ± 0.4 items/h, with rates similar for males (mean = 2.7 ± 0.3 items/h) and females (mean = 2.4 ± 0.3 items/h). The mean duration of the nestling period was 12.1 ± 0.5 d. Compared to many temperate species of tanagers, White-rumped Tanagers in our study had relatively small clutches, low nest attentiveness, and long incubation periods. As with other tropical species, such characteristics might be due to food limitation or high rates of nest predation. RESUMEN Cypsnagra hirundinacea está ampliamente distribuida desde el norte de Brasil, Bolivia y Paraguay, y está clasificada como vulnerable en el estado de Paraná y en peligro en el estado de São Paulo, Brasil. Actualmente poco es conocido sobre su biología reproductiva. Estudiamos el comportamiento reproductivo de C. hirundinacea en el cerrado (Sabana Neotropical) en la región central de Brasil desde el 2002 hasta el 2007. El periodo reproductivo se extiende desde mediados de agosto hasta mediados de diciembre. Los nidos en forma de copa estaban localizados principalmente en arboles del genero Kielmeyera a una altura promedio de 3.7 ± 0.3 (ES) m. El tamaño de la nidada vario entre uno y tres huevos y el periodo de incubación duro en promedio 16 ± 0.3 días. La incubación fue realizada exclusivamente por la hembra y comenzó después de la puesta del primer huevo. El promedio de atención al nido (porcentaje del tiempo en el nido por parte de la hembra) fue de 64 ± 0.08%. Los polluelos fueron alimentados por el macho, la hembra y, cuando estaban presentes, ayudantes. El promedio de la tasa de alimentación al nido fue de 5.2 ± 0.4 viajes/hr, con tasas similares entre el macho (promedio = 2.7 ± 0.3 viajes/hr) y la hembra (promedio = 2.4 ± 0.3 viajes/hr). El promedio de duración del periodo de polluelos fue de 12.1 ± 0.5 días. Comparado con muchas especies de tangaras de la zona temperada, C. hirundinacea tiene una nidada relativamente pequeña, baja atención al nido y un periodo largo de incubación. Pero las diferencias con otras especies tropicales en estas variables se pueden deber a variación en la disponibilidad de alimento o altas tasa de depredación. [source] Biogeography of common dolphins (genus Delphinus) in the Southwestern Atlantic OceanMAMMAL REVIEW, Issue 1 2010Maurício TAVARES ABSTRACT 1The common dolphins (genus Delphinus) have one of most problematic taxonomies and complex distribution patterns of all cetaceans. Although the taxonomy and the distribution seem to have been clarified somewhat in the eastern North Pacific and Indo-Pacific Oceans, many questions remain in the Southwestern Atlantic Ocean (SWA). We review the biogeography of Delphinus in the SWA. 2We reviewed data from strandings, incidental catches and sightings since 1922. Systematic surveys were conducted in five major areas. Twenty-one natural history collections were examined, and 135 skulls were measured. 3A total of 184 records of common dolphins were compiled. Delphinus apparently occurs in three stocks in the SWA: one located in northern Brazil and two from southeastern Brazil (,22°S) to central Argentina (,42°S). Two distinct patterns in habitat use were observed by depth: in southeastern Brazil, sightings were restricted to coastal waters with water depths ranging from 18m to 70m. On the other hand, in the area that extends from southern Brazil to Central Argentina (from 28°S to 42°S), sightings were recorded in deeper waters, ranging from 71m to 1435m, with the exception of occasional coastal sightings. The cranial analyses demonstrated that both short-beaked common dolphins Delphinus delphis and long-beaked common dolphins Dephinus capensis occur in the SWA. 4In the SWA, Delphinus seems to occur near areas of high productivity. One stock is associated with the productive waters discharged by the Amazon River and possibily with the coastal upwelling system off the coast of Venezuela, while the other stocks are associated with the Cabo Frio upwelling system and the Subtropical Convergence. Our results indicate that the current taxonomy does not adequately reflect the amount of variation within the genus in the world. [source] | ||||||||||