Polygyny and male parental care in Savannah sparrows: effects on female fitness

Summary To determine the effects of male mating status on female fitness, we compared the reproductive success, survival, and future fecundity of female Savannah sparrows (Passerculus sandwichensis) mated to monogamous vs. polygynous males in a 5-year study on Kent Island, New Brunswick, Canada. The proportion of males with more than one mate varied from 15 to 43% between years and sites. Polygynous and monogamous males fledged young of equal size in every year of the study. Females who shared paternal care with other females laid as many eggs per clutch and clutches per season as monogamously mated females. In most years polygynously mated females showed no delay in laying a second clutch, and they suffered no reduction in fecundity the following year. Recruitment of a female's offspring into the breeding population was generally independent of her mating status. Fitness costs of being mated to a polygynous male were only apparent in one year of the study, during which females mated to polygynous males had higher over-winter mortality than those mated to monogamous males. That same year, young raised by polygynous males were only one-third as likely to survive to reproductive maturity (as inferred by returns) as those raised by monogamous males. A male's mating status had no effect on his own survivorship. A male's mating status did not necessarily reflect his contributions to raising nestlings, which may partially explain why monogamously and polygynously mated females had equal fitness. At 35 nests the proportion of food deliveries brought by individual males varied from 0 to 75%; on average, males brought fewer than 30% of all food deliveries. Yet parental care by polygynous males was no less than that of monogamous males, at least at the nests of their primary females. Secondary females tended to receive less male assistance during the nestling stage, but their reproductive success was indistinguishable from that of primary females. Females feeding young without male assistance made as many food deliveries/h as did pairs in which males brought at least 30% of all food deliveries. Unassisted females did not suffer diminished fledging success or produce smaller fledglings. The benefits of polygyny for male Savannah sparrows are clear: polygynous males recruit more surviving offspring into the breeding population than monogamous males. The fitness of females, on the other hand, appears to be unaffected by whether their mate was monogamous or polygynous except in occasional years. Polygyny may be maintained in this population by the constraints of a female-biased sex ratio, the inability of females to predict a male's paternal care based on his morphology or behavior, the poor correlation between a male's mating status and his assistance at the nest, and inconsistent natural selection against mating with a polygynous male. Correspondence to: N.T. Wheelwright     

A Multi‐Agency Nutrient Dataset Used to Estimate Loads,Improve Monitoring Design,and Calibrate Regional Nutrient SPARROW Models1

Saad, David A., Gregory E. Schwarz, Dale M. Robertson, and Nathaniel L. Booth, 2011. A Multi‐Agency Nutrient Dataset Used to Estimate Loads, Improve Monitoring Design, and Calibrate Regional Nutrient SPARROW Models. Journal of the American Water Resources Association (JAWRA) 47(5):933‐949. DOI: 10.1111/j.1752‐1688. 2011.00575.x Abstract: Stream‐loading information was compiled from federal, state, and local agencies, and selected universities as part of an effort to develop regional SPAtially Referenced Regressions On Watershed attributes (SPARROW) models to help describe the distribution, sources, and transport of nutrients in streams throughout much of the United States. After screening, 2,739 sites, sampled by 73 agencies, were identified as having suitable data for calculating long‐term mean annual nutrient loads required for SPARROW model calibration. These sites had a wide range in nutrient concentrations, loads, and yields, and environmental characteristics in their basins. An analysis of the accuracy in load estimates relative to site attributes indicated that accuracy in loads improve with increases in the number of observations, the proportion of uncensored data, and the variability in flow on observation days, whereas accuracy declines with increases in the root mean square error of the water‐quality model, the flow‐bias ratio, the number of days between samples, the variability in daily streamflow for the prediction period, and if the load estimate has been detrended. Based on compiled data, all areas of the country had recent declines in the number of sites with sufficient water‐quality data to compute accurate annual loads and support regional modeling analyses. These declines were caused by decreases in the number of sites being sampled and data not being entered in readily accessible databases.     

Mitigating energy production-based carbon dioxide emissions in Argentina: the roles of renewable energy and economic globalization

Environmental Science and Pollution Research - The energy sector of Argentina is predominantly reliant on fossil fuels. Consequently, such fossil fuel dependency within the nation’s power...     

A SENSITIVITY ANALYSIS OF THE PALMER HYDROLOGIC DROUGHT INDEX1

ABSTRACT: The sensitivity of the Palmer Hydrologic Drought Index to departures from average temperature and precipitation conditions is examined. A time series of zero index values was calculated and then one monthly temperature or precipitation value was perturbed. The resulting time series shows the effects on the index of one anomalous value. Independent series were calculated for temperature anomalies of plus and minus 1, 3, 5, and 10F and for precipitation anomalies of 25, 50, 75, 125, 150, and 200 percent of normal for each calendar month for Colorado, Indiana, Nevada, New York, Oklahoma, South Carolina, South Dakota, Washington, and Wisconsin. Analysis of the time series showed that the period of time required for the index to reflect actual rather than artificial initial conditions could be more than four years. It was also found that the effects of temperature anomalies are insignificant compared to the effects of precipitation anomalies. In some cases, one anomalous precipitation value could result in established wet or dry spells that last for up to two years. Although not examined in detail, the time series suggest that distributions of index values may be asymmetrical and possibly bimodal.     

Influence of soil moisture and land use history on denitrification end-products

We investigated the effects of recent moisture history on the relative production of N2O and N2 during denitrification in soil from cropped and successional ecosystems. The soils were pedogenically identical but had been managed differently for the past decade. Sieved soils were amended with nitrate, glucose, and water. Long-wet and short-wet incubations received 80 and 0%, respectively, of prescribed water 2 d before incubation and the rest just before incubation. The N2O and N2 production and N2O mole fraction (N2O/[N2O + N2]) were measured using acetylene inhibition. The N2 production and soil 15N enrichment were measured by 15N-gas evolution. The response of N2O mole fraction to moisture history differed by ecosystem. Mean N2O mole fraction in the successional system was about the same for long-wet and short-wet treatments (0.34 and 0.33, respectively). For the cropped system, however, the N2O mole fraction was 0.36 for the long-wet and 0.90 for the short-wet treatment. Thus, in the cropped system a much smaller proportion of end product was N2O if soil had been wet for 2 d. For N2 fluxes, the isotope method gave the same pattern (r = 0.92) but only about one-third the magnitude, suggesting that N2 derived from two distinct pools. Differences in response of N2O mole fraction for successional and cropped soils may be due to differences in microbial communities. Further knowledge of ecosystem differences with respect to N2O mole fraction and recent moisture history may improve modeled estimates of local and global N2O fluxes.     

Extreme weather events and related disasters in the Philippines, 2004–08: a sign of what climate change will mean?

Being an archipelagic nation, the Philippines is susceptible and vulnerable to the ill-effects of weather-related hazards. Extreme weather events, which include tropical cyclones, monsoon rains and dry spells, have triggered hazards (such as floods and landslides) that have turned into disasters. Financial resources that were meant for development and social services have had to be diverted in response, addressing the destruction caused by calamities that beset different regions of the country. Changing climatic patterns and weather-related occurrences over the past five years (2004-08) may serve as an indicator of what climate change will mean for the country. Early recognition of this possibility and the implementation of appropriate action and measures, through disaster risk management, are important if loss of life and property is to be minimised, if not totally eradicated. This is a matter of urgent concern given the geographical location and geological characteristics of the Philippines.     

UV light induces Ag nanoparticle formation: roles of natural organic matter,iron, and oxygen

Nanoparticles occurring in the environment originate either from engineered, synthetically produced nanoparticles, or from naturally produced nanoparticles. The latter can be formed in natural media by light-induced reduction of metal ions in presence of natural organic matter, such as humic substances occurring widely in waters, soils and sediments. There is actually few knowledge on the effect of sunlight and of the nature of organic matter on nanoparticle formation. Therefore, we studied here the photoreduction of silver(I) ion to silver nanoparticles with and without ferrous ion under oxic and anoxic conditions, using humic and fulvic acids as proxies of natural organic matter. UV light-induced formation of silver nanoparticles was monitored up to 60 min by measuring surface plasmon resonance in air-saturated mixture and nitrogen-saturated mixture of silver(I) ion–organic matter. Results show that the surface plasmon resonance intensity was about 2.5 times higher in the nitrogen-purged solution mixture than the air-saturated solution. This finding suggests the oxygen-containing species had no major role in forming silver nanoparticles. Therefore, photo-driven formation of silver nanoparticles most likely involved photoactivation of silver(I) ion and natural organic matter complexes. We observed also that both iron(II) and iron(III) ions highly modified the surface plasmon resonance spectra of the particles with broader features. Results also reveal that in the presence of humic acid, the intensity of the surface plasmon resonance peak decreased by at least 50 %, while almost no change in the intensity was seen when fulvic acid was used. Overall, our findings demonstrate that the ligand–metal charge transfer process, affected by the nature of organic matter, i.e., humic acid versus fulvic acid, was influenced by redox iron species.