Papers by Enrique H. Weir L.
Memorias Do Instituto Oswaldo Cruz, 2023
BACKGROUND Physical factors can determine the level of triatomine abundance, but do not regulate ... more BACKGROUND Physical factors can determine the level of triatomine abundance, but do not regulate their population densities, and neither do natural enemies. OBJECTIVES To identify the processes associated with density-dependent triatomine population regulation. METHODS We setup a laboratory experiment with four interconnected boxes; the central box harbored Rhodnius prolixus bugs and one hamster. Stage 5 and adult densities of 10, 20, 30, 40, and 60 bugs per hamster, were replicated four times (except the density of 60 bugs). Hamster's irritability and several triatomine responses were measured: feeding, development time and longevity, mortality, fecundity, dispersal, and the net reproductive value (R o). FINDINGS Density had a statistically significant effect on irritability, but not on the percent of bugs feeding. Density was significant on blood meal size ingested in bugs that did not move between boxes, but not significant when the bugs moved. Density and irritability affected the proportion of stage 5 nymphs molting, and the proportion of adult bugs dying per day and over a three-week period. There was a highly significant effect of density and irritability on R o. MAIN CONCLUSIONS We showed that a density-dependent mechanism, acting through the irritability of the host, seems the most plausible process regulating populations in triatomines.
Revista de Biología Tropical/International Journal of Tropical Biology and Conservation; Vol. 46 (4) December 1998; 1135-1139, May 3, 2016
We evalualed the effect of interspecific competition between M. minense and C. flavipes larvae on... more We evalualed the effect of interspecific competition between M. minense and C. flavipes larvae on survival in both species and on the growth of M. minense. Interspecific competition was evaluated by the inoculation of M. minense larvae (l or 2 per host larvae: D. sachara lis) I to 5 days before or 3 to 8 days after the inoculatíon of C.flavipes eggs (one inoculation = 45 -50 eggs). AH experiments were done with ten replicas. We found a significant effect of ínterspecific competition on larval and pupal survival in both parasitoids and body weight in M. minense. M. minense dominated over C. flavipes, except when M. minense was inoculated 5 or more days after C. flavipes.
Ecological functions and economic value of the Neotropic Cormorant (Phalacrocorax brasilianus) in Los Olivitos Estuary, Venezuela
Environment and Development Economics, 2011
ABSTRACTWe present the ecological functions of cormorants and estimate the economic value of thes... more ABSTRACTWe present the ecological functions of cormorants and estimate the economic value of these functions to artisanal fishermen, as a valuation exercise for Neotropic Cormorants at Los Olivitos Estuary, Lake Maracaibo, Venezuela. Ecological functions were based on estimating the abundance, distribution and diet of cormorants; economic values were attached to a selection of goods, services and attributes. Based on available information, we selected four ecological–economic functions of cormorants: harvesting for food; contributors to fish diversity; indicators of fish schools; and contributors to fish biomass, due to guano production. Cormorants consumed nine commercial fish species. Mean consumption was 225 g/ind/day. All ecological–economic functions were positive except for the role as contributors to fish biomass. Total value of the cormorant population to fishermen was $5,429,703/year. Unlike many studies, our results show that Neotropic Cormorants have a negligible impact o...
Spatial Relations of Aquatic Bird Species and Water Management in the Lower Rio Grande Valley
... Laguna Atascosa, (2) Harlingen Sanctuary, (3) Sabal Palm Audubon Sanctuary, (4) Llano Grande ... more ... Laguna Atascosa, (2) Harlingen Sanctuary, (3) Sabal Palm Audubon Sanctuary, (4) Llano Grande Lake, (5) Santa Ana National Wildlife Refuge, (6) Bentsen Río Grande State ... To relate aquatic bird abundance and species richness to surface area of water, we drew upon ...
We evalualed the effect of interspecific competition between M. minense and C. flavipes larvae on... more We evalualed the effect of interspecific competition between M. minense and C. flavipes larvae on survival in both species and on the growth of M. minense . Interspecific competition was evaluated by the inoculation of M. minense larvae (l or 2 per host larvae: D. sachara lis) I to 5 days before or 3 to 8 days after the inoculation of C.flavipes eggs (one inoculation = 45 - 50 eggs). AH experiments were done with ten replicas. We found a significant effect of interspecific competition on larval and pupal survival in both parasitoids and body weight in M. minense . M. minense dominated over C. flavipes, except when M. minense was inoculated 5 or more days after C. flavipes .
Revista de Biología Tropical, 2007
In 1990-1996, we evaluated the relative importance of the Amazonian fly (Metagonystilum minense) ... more In 1990-1996, we evaluated the relative importance of the Amazonian fly (Metagonystilum minense) and the wasp (Cotesiaflavipes), in sugarcane crops, in Central Venezuela. We observed a significant decrease in relative abundance of Diatraea spp. when the Amazon fly abundance increased but not with the wasp abundance. Diatraea spp. abundance in presence of both parasitoids was similar to its abundance throughout the last 45 years, when only inundations of M. minense occurred. However a net effect by using both parasitoids was not evident. M. minense is probably the stronger pest control, because its more efficient in its host searching than C. flavipes and is better as competitor than the wasp.
Part of the Ornithology Commons, Population Biology Commons, and the Terrestrial and Aquatic Ecology Commons
Música de las Grullas: Una historia natural de las grullas de América
Boletin Del Centro De Investigaciones Biologicas, 2000
This paper reports for the first time the presence of Li roneca tenuistylis (Richardson, 1912), a... more This paper reports for the first time the presence of Li roneca tenuistylis (Richardson, 1912), a parasitic isopod of fish, in es tuarine waters ofthe Ciénaga de Los Olivitos, Zulia State, Venezuela. Specimens were captured in gill chambers on Anchovia clupeoides (Pisces: Engraulidae), feeding on the epithelium of the inner surface ofthe operculum. The presence of Lironeca tenuistylis in Venezuelan waters reinforces the knowledge ofthe estuarine isopod fauna in the country and extends the limits ofdistriburion in South America. A de scription ofthe species, an iIIustration, morfPhometric measures, geo graphical distribution and biogeographical comments are included.
International Journal of Tropical Biology and Conservation, Dec 1, 2001
Four pairs of the poorly understood tropical mockingbird Mimus gilvus were captured and color ban... more Four pairs of the poorly understood tropical mockingbird Mimus gilvus were captured and color banded at a grassland in Maracaibo, Venezuela in June 1997. Throughout the following 8 months, individuals were observed two days per week for 4 hours each. We recorded courtship behaviour, nest construction, incubation, parental care, territory defense and timing of reproductive cycle. Pairs lived in defined territories defended primarily by the male. Both sexes participated in nest building which began at the start of two rainy seasons: April and October. Between April and June, 80 % of nests were parasited by the shiny cowbird (Molothrus bonariensis). No parasitism was recorded in the later nesting season. Consequently, breeding success for the April and October seasons was 20 % and 83 % respectively. Only the female incubated and the mean clutch size was 2.2 eggs.
Boletin Del Centro De Investigaciones Biologicas, 1996
RESUMEN.-En Venezuela, donde los roedores cricéridos son plagas en cultivos de arroz y caña de az... more RESUMEN.-En Venezuela, donde los roedores cricéridos son plagas en cultivos de arroz y caña de azúcar, la madurez reproductiva normalmente se basa en un diagnóstico de la morfología externa. Nosotros realizamos un análisis histológico de las gónadas para obtener información más precisa acerca del grado de madurez sexual en machos de
We analyzed long-term demographic and environmental data to understand the role of large scale cl... more We analyzed long-term demographic and environmental data to understand the role of large scale climatic factors (the Pacific Decadal Oscillations [PDO]) and environmental factors in 3 regions of North America on natality and mortality of the remnant migratory whooping crane (Grus americana) population. This is an endangered species that spends winters at Aransas National Wildlife Refuge (ANWR) in Texas, breeds at Wood Buffalo National Park (WBNP) in Canada and "…uses Nebraska as a primary stopover". Long term data (27 years) of demography and environmental factors (PDO index, temperature and precipitation at WBNP, Nebraska and ANWR, pond water depth at WBNP, freshwater inflow, and net evaporation at wintering ground) were analyzed. Multiple regression analysis (path analysis) and qualitative analysis determined mechanisms (trends and extreme events) affecting whooping crane dynamics. Changes in mortality of eggs, chicks, juveniles during fall migration and at wintering grounds, and adults and subadults at wintering grounds, from April to November and annually, were correlated with environmental factors from the 3 different regions (except net evaporation at ANWR and temperature and precipitation in Nebraska during spring migration). Natality variability (brood failure and clutch size reduction) was explained by PDO, pond water depth in WBNP and environmental factors from the wintering ground that affected pre-breeding conditions and subsequently reproduction. Qualitative analysis showed synchrony of extreme events at ANWR and WBNP and extreme effects on whooping crane demography. Direct and indirect effects of these environmental factors are discussed at the population and individual level.
Abundancia de avifauna en el refugio de fauna silvestre y reserva de pesca Ciénaga de Los Olivitos, Venezuela
Boletin Del Centro De Investigaciones Biologicas, 2010
Preferencia de Metagonystilum minense (Diptera: Tachinidae) entre Diatraea saccharalis y Diatraea rosa (Lepidoptera: Pyralidae)
Boletin Del Centro De Investigaciones Biologicas, 1997
Bird species richness and abundance associated with water availability and climate in south-central Nebraska
The Central Platte River and Rain Water basins at south-central Nebraska, USA, are remarkable hab... more The Central Platte River and Rain Water basins at south-central Nebraska, USA, are remarkable habitats for both aquatic and terrestrial bird throughout the year. Birds use these habitats as stopovers during spring and fall migrations, breeding grounds, and wintering grounds. In this study I ...
[Reproduction of the bird Mimus gilvus (Passeriformes: Mimidae) in Maracaibo, Venezuela]
Revista de biología tropical
Four pairs of the poorly understood tropical mockingbird Mimus gilvus were captured and color ban... more Four pairs of the poorly understood tropical mockingbird Mimus gilvus were captured and color banded at a grassland in Maracaibo, Venezuela in June 1997. Throughout the following 8 months, individuals were observed two days per week for 4 hours each. We recorded courtship behaviour, nest construction, incubation, parental care, territory defense and timing of reproductive cycle. Pairs lived in defined territories defended primarily by the male. Both sexes participated in nest building which began at the start of two rainy seasons: April and October. Between April and June, 80% of nests were parasited by the shiny cowbird (Molothrus bonariensis). No parasitism was recorded in the later nesting season. Consequently, breeding success for the April and October seasons was 20% and 83% respectively. Only the female incubated and the mean clutch size was 2.2 eggs.
CANCELLED - Whooping crane migration and stopover decision, a conceptual model
Background/Question/Methods The endangered Whooping Crane (Grus americana), had increased from 15... more Background/Question/Methods The endangered Whooping Crane (Grus americana), had increased from 15 birds in 1941 to 281 individuals by the winter of 2010-2011. The population that migrates from Canada to Texas, has exhibited exponential growth over the past seven decades, notwithstanding a few short periods of decline. Recent studies have shown that “bad” years have been partially attributed to climatic and abiotic factors in the wintering and breeding grounds (extreme temperature, freshwater inflow, pond water depth, PDO). However, an analysis of all possible variables affecting whooping cranes during migration and along the central flyway has not been developed. We built a conceptual model for the entire life cycle of the whooping crane including migration where we established a hierarchical structure of abiotic and biotic factors that could be correlated to the historical population dynamics and also to their decision on stopover selection. We reviewed all databases and informatio...
Uploads
Papers by Enrique H. Weir L.