Bird diversity and selection of protected areas in a large neotropical forest tract

The unbroken primary rain forest currently covering the interior ofFrench Guiana still offers a unique opportunity to establish a network of largeprotected areas. Bird species richness was surveyed within 20 study areasspreadover the country to assess the relative abundance and frequency of occurrenceofforest interior and natural gap taxa (391 species, excluding raptors andnon-resident birds). Richness, rarity, restricted range, hot spot andconservation value algorithms were used to rank sites in decreasing orders ofimportance and draw sets of survey sites likely to maximize bird diversity. Inmost sets from different methodological approaches, the southern regionconsistently emerged as a priority area for conservation, with the centralmountain range contributing some specialized taxa and the northern regionincorporating additional species, mostly from marginal habitats and moretypicalof the nearby coastal zone. Estimates of areas likely to preserve an almostcomplete sample of the regional biodiversity amounted to about 1–2millionhectares, either in one large area (national park) or divided into 2–3reserves overlapping regional hot spots. However, representation of all speciesand habitats in a protected area system is not an assurance of long-termviability when minimum viable population sizes and demographic patterns arelittle known, and when the risks and impacts of persistent human disturbancessuch as mining, logging and hunting are growing.     

The influence of soil cover organization on the floristic and structural heterogeneity of a Guianan rain forest

The impact of soil cover organization on the forest community has been studied in a 19-ha tract at Piste de St Elie station in French Guiana. 195 species each represented by at least 10 individuals were chosen from records of the position, diameter at breast height (dbh) and precise identification by botanical sampling of 12104 ligneous plants (dbh 10 cm).Spatial variations in the soil were mapped using the method proposed by Boulet et al. (1982). The soil mapping units correspond to the successive stages of evolution of a currently unbalanced ferralitic cover. These stages describe firstly the thinning by erosion of the microaggregated upper horizon and secondly the mineralogical changes under more or less extended hydromorphic conditions. The degree of evolution of ferralitic cover is also related to the hydrodynamic functioning and chemical properties of the soil. Geological substrate, topography and slope have also been taken into account.Analysis of the influence of environmental variables on plant cover has been performed using the Ecological Profiles method and Correspondence Analysis (CA) of the table of ecological profiles.The forest community seems to be dependent on the soil and the topographical features that govern it. There are significant, exclusive soil-species links for each soil functioning mapping unit. However, the highest proportion of significant positive links is connected with a thick microaggregated horizon (25%). Several species are of real value as indicators and more particularly enable differentiation between the forest stands of typical ferralitic soil and the ones of thinned out, transformed and hydromorphic soils. The CA of the species by environmental variables matrices reveals two significant factorial axes. The first can be associated with the drainage mainly related to the thinning of the soil and the second with the hydromorphic conditions related to the topography. The vegetation ordination of the stands ( 0.25 ha) delimited in the various soil domains clearly shows that changes in ferralitic cover and in particular the transition from soil with deep vertical drainage to soil with superficial lateral drainage is accompanied by substantial changes in the forest community.     

The influence of epiphyte cover on branch temperature in a tropical tree

The air temperature around three branches loaded with epiphytes in a tropical lowland rain forest in French Guiana was measured from mid-June to mid-July 1997. These data represent the first direct measurements of temperature close to epiphyte-loaded branches in a tropical lowland forest. The epiphytic biomass of one of the branches was removed after two weeks of measurements. These differences in stripped versus unstripped branch temperatures were positive during day time. A maximum difference of 4.8 °C was measured on a single sunny day; the maximum of four mid-day hours averaged over all days was 2.3 °C. Maxima were determined at locations close to the branch, representing high accumulations of humus, while nearly no differences were detected 75 cm away from the branch. At night, the temperature was cooler after epiphyte biomass removal; differences were up to –0.5 °C. Close to the branch, evaporation of stored water in humus cools the environment while latent heat transformation on epiphyte surfaces raises temperature. Shading under a branch prevents heating. Epiphytes reduce air circulation, keeping unheated air on branch undersides. At night, auto-heating of humus may occur through increased rates of respiration.     

Report on wind dispersal in a lowland moist forest in central French Guiana

An analysis of the flowering plant flora of a lowland moist forest in central French Guiana reveals 298 species with adaptations for wind dispersal. This represents 16.2% of the flowering plant flora and 9.8% of the class Magnoliopsida (dicotyledons). The most diverse wind-dispersed families are the Orchidaceae in the Liliopsida (monocotyledons) with 135 species and the Bignoniaceae in the Magnoliopsida with 37 species. The wind-dispersed species of central French Guiana have evolved either small, dust-like seeds, fruits or seeds with various kinds of wings, fruits or seeds with tufts of hairs, or expanded wing- or parachute-like persistent calyces. Most wind-dispersed species, among the liliopsids, are epiphytes and, among the magnoliopsids, trees or lianas. In central French Guiana, collections of these species with mature diaspores have been gathered most often in October and March, the months with peak wind velocities. In contrast, collections from June and July, when wind velocities are at a minimum, are rare.     

Trophic partitioning in tropical rain forest birds: insights from stable isotope analysis

Bird communities reach their highest taxonomic and trophic diversity in tropical rain forest, but the use of different foraging strategies to meet food requirements in such competitive environments is poorly understood. Conventional dietary analyses are poorly suited to investigate dietary patterns in complex systems. We used stable carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N) isotope analysis of whole blood to examine avian trophic patterns and sources of diet in the tropical rain forest of Los Tuxtlas, Veracruz, Mexico. We used stable nitrogen isotope analysis to delineate trophic levels, and stable carbon isotope analysis to distinguish the relative contribution of C-3 and CAM/C-4 ultimate sources of proteins to diets. There was large inter- and intraspecific variation in whole blood ¹³C and ¹⁵N values in 23 species of birds. Stable nitrogen isotope analysis separated birds into several trophic levels, including species that obtained their dietary protein mostly from plants, insects or a combination of both food sources. Stable carbon isotope analysis showed that most birds fed on C3-based foods but Stub-tailed Spadebills (Platyrinchus cancrominus) included C-3- and C-4/CAM-specialist individuals. Our analyses provided insights into the nutritional contribution of plant and animal sources of protein and distinguish their photosynthetic origin over relatively long average time periods.     

Microbiological condition and shelf life of meat from hunted game birds

Hunted game birds (eight partridges, nine wood pigeons, 25 quails, 16 chilled and 16 frozen–thawed pheasants) were processed according to “Good Manufacturing Practice” rules. Microflora of skin, intestinal content and meat cuts (breast and thigh, both fresh and stored in vacuum package) was analysed. Listeria monocytogenes, Salmonella sp. and Campylobacter sp. were not recovered from any sample. Log microbial numbers on skin or in intestines were not significantly related to those on meat cuts. With the exception of pigeons, microbial numbers of the two meat cuts did not differ significantly (p > 0.05), and no significant increase in microbial numbers in vacuum-stored meat was found; the same applied to frozen–thawed compared to chilled pheasants. On meat, average total viable counts were <4.00 log cfu/cm² with a maximum of 6.48 log cfu/cm². Median Escherichia coli numbers were <2.00 log cfu/cm², maximum was 4.48 log cfu/cm². Meat cuts obtained from partridges, quails and pheasants demonstrated a shelf life of 1 week, provided they were kept vacuum-packaged at 0°C to 1°C.     

Epizoochorous dispersal by barbs, hooks, and spines in a lowland moist forest in central French Guiana

An analysis of the flowering plant flora of a lowland moist forest in central French Guiana reveals 25 species with adaptations for epizoochorous dispersal by barbs, hooks, or spines (stick-tights). This represents 1.5% of the flowering plant flora. Stick-tights are represented among the monocotyledons of the flora of central French Guiana by five species of Poaceae. The Fabaceae and Asteraceae, each with six species with stick-tight dispersal, are the richest families of flowering plants in terms of stick-tight dispersal in central French Guiana. This region possesses numerous potential mammal and bird dispersal agents, therefore it is a puzzle why stick-tight dispersal, especially among species of the canopy, is not more frequent.     

Fruit choice by red howler monkeys (Alouatta seniculus) in a tropical rain forest

This paper presents and discusses aspects of fruit selectivity by red howler monkeys (Alouatta seniculus) in relation with morphological characteristics of fruits. These data are used to provide an answer to the following questions: which are the fruit characteristics that lead fruit choice of howler monkeys and to what extent fruit characteristics play a role in seed dispersal by monkeys? The frugivorous diet of a troop of red howler monkeys was determined during a 2-year field study in French Guiana. The selection of fruit by howler monkeys was analyzed in relation to the fruit availability. Results showed that, although consumption followed availability, fruit species could be classified in three categories according to their selection ratio (percentage of consumption/percentage of abundance) as “high ranking,” “middle ranking,” and “low ranking” species. Also, the 97 species of fruit eaten by the monkeys were grouped according to the morphological characteristics thought to influence the monkeys' choice. This showed that howler monkeys consumed essentially fruits with juicy pulp, bright color, and a small number of well-protected seeds. Most of high ranking species had medium-sized fruits with yellow color, and low ranking species often had small fruits. However, howler monkeys are associated with the dispersal of seeds from fruit with a hard and indehiscent pericarp and/or large seeds, like those of the Sapotaceae family. Consequently, they can be considered as “specialized” frugivores for this fruit syndrome. © l996 Wiley-Liss, Inc.     

Habitat relationships of forest birds on Tutuila Island, American Samoa

Aim Our knowledge of landbirds on tropical Pacific islands is often comprised of brief, one-time surveys. We know little of species’ habitat preferences, and this information is critical for understanding the resource requirements or population status of native species and the impacts of human activity on island birds. Location Tutuila Island, American Samoa. Methods The spatial patterns in forest birds were investigated. This island harbours large tracts of native forest, a variety of disturbed and non-native forests, and some relatively healthy bird populations. The distribution of birds was correlated with forest types using habitat data collected at fifty-seven sites and avian census data collected monthly for 1–4 years at these sites. Results Differences in location and in vegetation structure and composition between native and non-native habitats are important influences on the distribution of birds on Tutuila. Among native species, for example, the purple-capped fruit-dove (Ptilinopus porphyraceus Temminck) is dependent upon native habitat, the Samoan starling (Aplonis atrifusca Peale) occurs in all habitats, and the cardinal honeyeater (Myzomela cardinalis Gmelin) is more abundant in low elevation, non-native habitat. Conclusions This research reinforces the importance of quantitative assessment of habitat relationships in the study and conservation of Pacific birds.     

Seasonality of reproduction in the three largest terrestrial rodents of French Guiana forest

We investigated the main life history of the three largest terrestrial rodents of French Guiana forest: the acouchy (Myoprocta exilis), the agouti (Dasyprocta leporina) and the paca (Agouti paca), using data collected during several years. There were noticeable differences among the species in sexual maturation and degree of seasonality in reproduction. Percentage of pregnant females, births and juveniles, and body weight of juveniles decreased progressively from the acouchy, through the agouti to the paca. The acouchy was by far the most seasonal: no births occur in the period August–October, 56% of births were encountered in November–January; consequently, young form an unique cohort in the population. The agouti was also seasonal, but to a lesser degree. Newborns appeared in every period of the year in paca, without any formation of cohort of young. These differences tended to be linked to the seasonal importance of fruits in diets, the most aseasonal species having the most diversified diet during the poor fruit season.

Zusammenfassung

Jahreszeitliche Fortpflanzung von den drei größten terrestrischen Nagern im Regenwald von Französisch GuayanaDie Untersuchungen beziehen sich auf die wichtigsten Merkmale der Lebenszyklen der drei größten terrestrischen Nager, Acouchi, Aguti und Tieflandpaka, im Regenwald von Französisch Guayana, unter Verwendung von über mehrere Jahre währenden Beobachtungen, die beachtenswerte Unterschiede in bezug auf Geschlechtsreife und Fortpflanzung aufzeigen. Fortpflanzung und Populationsstruktur, wie Prozentsatz trächtiger Weibchen, Geburten, Auftreten von Jungen sowie deren Körpergewicht verringern sich kontinuierlich von Acouchis über Agutis hin zu Tieflandpakas. Während Acouchis die bei weitem am stärksten ausgeprägte jahreszeitlich gebundene Fortpflanzung mit 56% der Geburten in den Monaten November bis Januar zeigen, konnten von August bis Oktober keine Geburten beobachtet werden. Demzufolge treten die Jungen in der Population als eine einheitliche Altersklasse auf. Eine periodische Fortpflanzung zeigen auch Agutis, wenn auch weniger ausgeprägt, wohingegen bei Tieflandpakas über das gesamte Jahr hinweg Junge geboren werden, ohne jegliche Bildung von einer Altersklasse. Diese Unterschiede scheinen an die jahreszeitlich bedingte Produktion von für die Ernährung wichtigen Früchten gebunden zu sein, wobei die am wenigsten periodische Art in der früchtearmen Zeit das breiteste Nahrungsspektrum aufweist.     

Effects of Single and Recurrent Wildfires on Fruit Production and Large Vertebrate Abundance in a Central Amazonian Forest

Wildfires are an increasing threat to tropical rainforests, yet little is known about their effects on fruit production and forest wildlife. We examined the effects of both single and recurrent wildfires on fruit production and large vertebrate abundance in a central Amazonian terra firme forest for 3 years following a large fire event. The estimated mortality of 42 and 74% of stems ≥10 cm in once- and twice-burnt forest led to a substantial loss of fruiting tree basal area (29 and 62% were lost in once- and twice-burnt forest, respectively) and crown coverage of fruiting woody lianas (89 and 97% were lost in once- and twice-burnt forest, respectively). Some important tree families producing fleshy fruits were less abundant than expected in once- and twice-burnt forest, suggesting that tree mortality was non-random in terms of species composition. Asynchronous fruit production was affected, and burnt forest transects sustained a much lower fruiting basal area, and fewer fruiting species during the dry season period of fruit scarcity. The number of fruiting trees in once- and twice-burnt forest was higher than the number predicted from actual levels of tree mortality recorded in each fire disturbance treatment, suggesting some surviving trees which may have benefited from higher irradiance levels and lower competition for resources. Many large frugivores and other vertebrate species declined in response to single fires, and most primary forest specialists were extirpated from twice-burnt forest, which sustained a higher number of species associated with second growth and other disturbed habitats.     

Crown typology and the identification of rain forest trees on large-scale aerial photographs

This paper assesses the potential of large-scale aerial photographs for the identification of rain forest trees. Colour slides at 1: 3000 scale were acquired in French Guiana, above the canopy of a 25 ha study site where trees had already been identified. Firstly, the stereoscopic analysis of photographic prints served to establish a typology of the crowns, based on seven main classes of criteria: crown size, crown status, crown contour, crown architecture, foliage cover, foliage texture and colour, completed where possible by information on phenology. The terminology chosen was based on those proposed in previous studies. Secondly, a smaller area of 5 ha was delimited in the field, on which 15 tree categories (vernacular names) represented by 5 crowns or more on the photographs were selected. For each category, a standard crown was described using terminology previously defined. Twelve tree categories, including first and second class commercial timbers, displayed specific characteristics allowing them to be identified on aerial photographs. Further analyses will be undertaken in the future to measure the success of this identification method. This method may be applied for the recognition of particular species of interest: commercial, rare, endemic or key-stone species. Phenological data, as well as information on crown architectural development, can also be retrieved from aerial photographs, bringing new prospects for a better knowledge of crowns biology and their functional role in the forest ecosystem.     

Old growth and secondary forest site occupancy by nocturnal birds in a neotropical landscape

High rates of old growth (OG) forest destruction and difficult farming conditions result in increasing cover of secondary forests (SF) in the Amazon. In this setting, it is opportune to ask which animals use newly available SF and which stay restricted to OG. This study presents a comparison of SF and OG site occupancy by nocturnal birds in terra firme forests of the Amazon Guianan shield, north of Manaus, Brazil. We tested species-specific occupancy predictions for two owls ( Lophostrix cristata/Glaucidium hardyi ), two potoos ( Nyctibius leucopterus/Nyctibius griseus ) and two nightjars ( Caprimulgus nigrescens/Nyctidromus albicollis ). For each pair, we predicted that one species would have higher occupancy in OG while the other would either be indifferent to forest type or favor SF sites. Data were collected in 30 OG and 24 SF sites with monthly samples from December 2007 to December 2008. Our analytic approach accounts for the possibility of detection failure and for spatial autocorrelation in occupancy, thus leading to strong inferences about changes in occupancy between forest types and between species. Nocturnal bird richness and community composition were indistinguishable between OG and SF sites. Owls were relatively indifferent to forest type. Potoos followed the a priori predictions, and one of the nightjars ( C. nigrescens ) favored SF instead of OG as predicted. Only one species, Nyctib. leucopterus , clearly favored OG. The landscape context of our SF study sites, surrounded by a vast expanse of continuous OG forest, partially explains the resemblance between SF and OG fauna but leaves unexplained the higher occupancy for SF than OG sites for several study species. The causal explanation of high SF occupancy remains an open question, but the result itself motivates further comparisons for other groups, as well as recognition of the conservation potential of SF.     

Seed dispersal by red howling monkeys (Alouatta seniculus) in the tropical rain forest of French Guiana

A 2-year field study of the frugivorous diet of a howling monkey troop, in a tropical rain forest in French Guiana, shows that they disperse by endozoochory ≥95% of plant species from which they eat ripe fruit. Passage through the digestive tract of howlers does not significantly modify the germination success of most plant species samples. Their low digestion rate (X = 20 hr 40 min) is the ultimate cause of a bimodal defecation rhythm that results in the concentration of 60% of defecations being deposited under sleeping sites. The distance of seed dispersal can reach more than 550 m from parent trees,with a mean of 260 m. Although howling monkeys consume fruits differing in morphological characteristics, they are particularly able to disseminate seeds of species whose fruits have a hard and indehiscent external coat or large seeds or both. In French Guiana, they may be especially important dispersers of the Sapotaceae with fruits that simultaneously present both characteristics.     

Population structure and mitochondrial DNA variation in sedentary Neotropical birds isolated by forest fragmentation

The current worldwide concern about tropical deforestation raises questions about the sustainability of avian populations in isolated forest fragments. One of the most important issues concerns the sizes of forest fragments necessary to maintain populations and the genetic variation within them. We address this by: (1) using mtDNA sequence variation to infer aspects of the population structure of four species of understory birds from four sites in southern Costa Rican rainforest; and (2) determining whether forest fragmentation that has occurred in the last 50 years has had an effect on the amount of within-population variation for the species in question. High levels of between-population differentiation (D_xy) were found over a relatively small geographic scale (<130 km) for white-breasted wood-wren (Henicorhina leucosticta), bicolored antbird (Gymnopithys leucaspis), and gray-headed tanager (Eucometis penicillata), suggesting that these species are highly sedentary and exhibit strong female philopatry. No mtDNA variation was found in Plain Antvireo (Dysithamnus mentalis). In all three of the polymorphic species there was a significant decrease in mtDNA nucleotide diversity in populations isolated by forest fragmentation as compared to populations in contiguous primary forest. Even in relatively large (250–1000 ha) forest reserves, sedentary avian species have lost roughly half (range 43–85) of the nucleotide diversity in mtDNA over a relatively short period of time. Our results indicate that sedentary avian species in forest fragments isolated by clearing have undergone severe reductions in effective population size due to population bottlenecks perpetuated by prolonged isolation and potential edge effects.     

Effects of an ENSO-related fire on birds of a lowland tropical forest in Sumatra

Comparisons of bird community composition in burned and unburned areas of a lowland tropical rainforest in Sumatra, Indonesia indicated the following during the first 5 years after burning: (1) original burn severity strongly affected bird community composition at both the genus and family levels; (2) bird community composition continued to change progressively away from immediate post-burn composition in medium and severely burned forest as well as adjacent unburned forest; and (3) the degree of impact was both taxon and guild specific, with understory insectivores most detrimentally affected. Although species richness may temporarily increase in burned areas, this study suggests that multiple wildfires will lead to a decline in diversity over a large scale as birds of open fields replace interior forest specialists.