Rains In April Research Articles

Seasonal and diel patterns of total gaseous mercury concentration in the atmosphere of the Central Valley of Costa Rica

Abstract Monitoring of Hg in the atmosphere near volcanoes is limited with no previous data for Costa Rica. Seasonal and daily patterns of total gaseous mercury (TGM) were observed at the main sampling location at the Universidad Nacional, Heredia, Costa Rica. The area (lat. 10.000230 long. −84.109499) is located in the Central Valley of Costa Rica and is 27 km SE of the Poas volcano (lat. 10.199486 long. −84.231388). Measurements were made from May 2008 to May 2009 at this location with some additional values obtained at other sites near the Poas volcano including San Luis and Grecia as well as near, Turrialba and Irazu volcanoes. Total gaseous Hg was determined in samples collected at a height of 2 m using the Tekran 2537A (Tekran Inc.) gas-phase Hg vapor analyzer. Meteorological data (temperature, relative humidity, wind speed, wind direction, radiation and precipitation) were obtained from the airport weather station located at Alajuela. Monthly precipitation is typically 85 mm during the dry season (December to April) with winds from the west. The wet season begins in late April and continues to December with monthly rainfall of 328 mm and winds from the NE. The annual mean temperature is 20 °C. With the onset of the wet season TGM increased from typical values near 10 to 905 ng m −3 . Measurements made within 5 km of the Poas volcano were higher than at Heredia at that time. Diel values measured at the university site increased until midday along with temperature and radiation. Relative humidity showed a reciprocal pattern. It was found that high values of TGM were not related to wind velocity or direction. The strong diel pattern increased with sunrise, peaked at midday and was lowest during the night time. It would seem that Hg 0 from the volcano is oxidized and is deposited to the soils during the dry season when winds are blowing from the volcano. With the onset of heavy rains in April, Hg in the soil is reduced and re-volatilized resulting in the high levels in the atmosphere. Values at other volcano sites were provided. The role of atmospheric pollutants such as H 2 O 2 and O 3 should be included in future studies as they may result in oxidation of reduced Hg. The instability in the air masses may also be a factor and local pollution sources may result in high levels that is emitted from the volcanoes of Hg being circulated to ground level as radiation intensity increases.

Spatial and seasonal variations of fish assemblages in mangrove creek systems in Zanzibar (Tanzania)

Spatial and seasonal variations of fish assemblage composition were studied in three non-estuarine mangrove creeks of Zanzibar (Tanzania). Fish were collected monthly for one year at three sites (lower, intermediate and upper reaches) in each creek using a seine net (each haul covering 170 m 2). Density, species number and diversity of fish were all higher at sites with dense cover of macrophytes (seagrass and macroalgae) than over unvegetated sandy sites. In general, fish assemblages mainly comprised juveniles of a few abundant taxa, e.g. Mugil cephalus, Mugilidae spp. and Leiognathus equulus at sites with mud substratum and Gerres oyena, Lethrinus harak and Sillago sihama at sites dominated by macrophytes. Multivariate analyses revealed significant separations in fish assemblage composition within the two creeks where the bottom substratum differed among sites. Overall, season seemed to have little effect on density, species number, diversity index ( H′) and assemblage structure of fish. Water condition variables were also relatively stable across the season, although a short-term fluctuation primarily induced by decreased salinity, occurred during the heavy rains in April and May. Fish assemblage structure was not significantly affected by any of the abiotic factors tested. However, significant regressions were found between the other fish variables and environmental variables, but since these associations were mostly species-specific and generally inconsistent, we suggest that the overall distribution patterns of fish were mainly an effect of particular substrate preferences of fish species rather than contemporary water conditions.

Seasonal and diurnal variability in sap flow intensity of mature sessile oak (Quercus petraea(Matt.) Liebl.) trees in relation to microclimatic conditions

In this study sap flow dynamics of mature sessile oak trees (Quercus petraea) in a marginal sessile oak-turkey oak forest was investigated in 2009. That year spring was dry without significant rain in April and May and the driest month was August. Due to the extreme weather conditions the volumetric soil water content (SWC) of upper 30 cm was low on experimental days in May (0.13-0.14 cm3 cm-3) but it reached the lowest value in August (0.08 cm3 cm-3). Sap flow was measured in a dominant and a co-dominant tree by heat dissipation method from 26 March till 30 October. In the present paper several three-day long periods of the continuous seasonal recordings were chosen to represent the effects of typical weather conditions and different stages of canopy development on sap flow dynamics. The daily maximum sap flow density values of dominant and co-dominant trees were similar (0.30-0.32 cm3 cm-2 min-1) in moist period (July). Rains and transient increase of SWC after proceeding drought resulted in change of diurnal course of sap flow in experimental days of July. In this period dominant trees also showed considerable sap flow (0.19 cm3 cm-2 min-1) during night hours and short sap flow peaks in early morning (6:00 to 8:00 a.m.) indicating the refilling of desiccated tissues. After the progressive drought in August the daily maximum sap flow density decreased to 0.07 cm3 cm-2 min-1 in dominant tree and to 0.12 cm3 cm-2 min-1 in the co-dominant. Both trees exhibited gradual stomatal closure from morning hours.

Which Is to Say, and: This Life

Which Is to Say, and: This Life David Graham (bio) Which Is to Say I’m nostalgic for my thirties, which is to say, it’s all a little fuzz-edged now, where we lived, how it felt, what we said to our thirty-something pals at those long parties we’d throw, everyone all glistening, getting gin-and-tonic’d out on the unburned lawn, maybe some sweaty volleyball or Frisbee, for we were quite young, which is to say, we felt old. We’d stock each other’s fridges with Carlo Rossi and Old Milwaukee. We’d live on nuts and chips. Sure, we’d wake all cottony and throbbing, but that was a sign of intensity. Our bones were strong. Which is to say, they were not. We maybe guzzled too much too often for clearly remembering how great it was to be thirty-something, with, yes, the yearning urgent flesh, and of course some major flirtation, not all of it harmless. Which is to say, there were long, loud, torn-scab breakups, there was shrieking in [End Page 95] backseats and bedrooms, which is to say, we mostly lost one half of each breaking-up couple, you had to choose, you needed to say wise and sympathetic things, but only to her, or only to him. You had to vote. And once you’ve sat handing tissues to a grown man who hasn’t left your sofa for ten days straight, and heard of every kinky regrettable thing, well, you get a bit weary, which is to say, you remember all this imperfectly at best, this rosy amorphous feeling now being a vast oversimplification based on the inscrutable holy mystery of time, and yes, perhaps a tad more vodka than was strictly helpful. So those were not simpler times, not happier, they were just twenty-something years ago, which is to say, precious as any lost gem or bent key. [End Page 96] This Life Somewhere in daydreamery I’m pedaling my furious bike down a street that isn’t as steep as I think it is, pedaling toward nothing as big or fascinating as I hope it might be, and don’t you dare smile at that, or understand. I don’t yet fathom it myself, see? And I was there. The grit of last winter’s road sand washes down in April rains, forms street-corner deltas for a boy to sideswipe at full tilt, then wipe out spectacularly. What he was pedaling toward turns out to involve a hip cast, bandages, and lots of morphine. Bad caseof road rash, he’ll call it in his later, cool phase, but then it was apocalypse now, bombs reducing daydream-land to smoking rubble. There is no self-pity like his. Or maybe there is, but he’ll never know, locked as he is in his cowboy bedroom with Get Wells tacked to the cork board and a mess of comic books splashed across the bedclothes. [End Page 97] He’ll remember it all, but vaguely, quite possibly wrongly, those being the days before sex, before Thoreau, before roach clips, before Hendrix and The Doors of Perception creaking wide. Long before his glee that Hot Tuna is really Hot Shit, and that Steely Dan’s a dildo. It was all quite previous and hitherto, yet also shifty as to tense, as you’ve seen: akin to dream or daydream in that regard, yet otherwise brutal and gritty as no dream can be, this ongoing vanishment, this once-only show, this life. David Graham David Graham is the author of six collections of poems, most recently Stutter Monk (Flume P), and an essay anthology coedited with Kate Sontag, After Confessions: Poetry as Autobiography (Graywolf P). “If literature is news that stays news, what will remain of the Boomer generation, after all the dust settles, are the aches, complaints, joys, hopes, vanities, and uncertainties of any generation. I don’t think we’re special at all, just numerous.” Copyright © 2009 University of Nebraska Press

Population dynamics of white grubs (Coleoptera: Scarabaeidae) in the rose environment of Northern Bangalore, India

Faunal composition of scarabaeids associated with rose cultivation in Bangalore districts of Karnataka (India) was investigated. During the field survey, thirteen species of scarabaeid beetles belonging to nine genera representing three sub families: Melolonthinae, Rutelinae, and Cetoniinae were recorded. Maximum of five species belong to subfamily Melolonthinae and each three species belong to Rutelinae, and Cetoniinae. Among the identified species, Holotrichia seerata, Schizonycha ruficollis, Anomala bengalensis, and Adoretus versutus were found to be the most dominant leaf feeders and Maladera sp. and Apogonia ferruginea was found to be infesting more on flowers on rose. The scarabaeids adults’ emergence began after the 1st rain in April and it was continued up to the last week of September in Bangalore condition. Maximum numbers of adults were recorded between 19.00 and 19.30 hrs and thereafter no emergence/ a little emergence was noticed from each species of scarabaeids. The degree of leaf damage caused by H. seerata, S. ruficollis, and A. versutus were significantly more on rose leaf irrespective of presence or absence of flowers. The outcome of the study may be helpful in pest management especially of rose plantation. Keywords: Beetles, rose, floriculture, pest management.

Disease–Weather Relationships for Powdery Mildew and Yellow Rust on Winter Wheat

Key weather factors determining the occurrence and severity of powdery mildew and yellow rust epidemics on winter wheat were identified. Empirical models were formulated to qualitatively predict a damaging epidemic (>5% severity) and quantitatively predict the disease severity given a damaging epidemic occurred. The disease data used was from field experiments at 12 locations in the UK covering the period from 1994 to 2002 with matching data from weather stations within a 5 km range. Wind in December to February was the most influential factor for a damaging epidemic of powdery mildew. Disease severity was best identified by a model with temperature, humidity, and rain in April to June. For yellow rust, the temperature in February to June was the most influential factor for a damaging epidemic as well as for disease severity. The qualitative models identified favorable circumstances for damaging epidemics, but damaging epidemics did not always occur in such circumstances, probably due to other factors such as the availability of initial inoculum and cultivar resistance.

Composition, Abundance and Seasonality of Zooplankton in Mida Creek, Kenya

Keywords: zooplankton, phytoplankton, composition, abundance, diversity, Mida creek, Kenya. Samples were collected monthly at four fixed stations in Mida creek from May 1996 to April 1997, in order to determine the species composition, abundance and diversity of phytoplankton and zooplankton collected with 20- and 332-mm mesh size plankton nets respectively. Sampling also included measurement of salinity and temperature. Peaks in phytoplankton abundance occurred in May and January, following the long rains in April–May and the short rains in November–December. Zooplankton densities followed the phytoplankton peaks with the main peak occurring in February after the major phytoplankton bloom. Similarly, smaller peaks occurred in May and March. Copepods dominated the zooplankton forming up to 60% of total species composition. High zooplankton diversity occurred in June–July when zooplankton abundance was lowest as compared to February–March. Spatially, the highest diversity was recorded at station 1 located towards the open sea as compared to the other stations located farther inshore. Western Indian Ocean Journal of Marine Sciences Vol.2(2) 2003: 147-155

Implications of Warm Temperatures and an Unusual Rain Event for the Survival of Ringed Seals on the Coast of Southeastern Baffin Island

We recorded an unusually warm period in early April 1979 along the coastline at the end of the Hall Peninsula on southeastern Baffin Island, Nunavut. Maximum temperatures remained at or above freezing for almost a week, and rain fell on our field camp on three consecutive days. In contrast, meteorological data collected from three nearby coastal stations (Brevoort Island, Cape Dyer, and Resolution Island) between 1950 and 1992 indicated that the mean minimum and maximum air temperatures for the month of April are normally 10-20°C cooler than the averages we recorded at our camp. Periodic warming to near freezing, probably due to the maritime influence of nearby open water in Davis Strait, occurs in this area in late March and early April, but not usually to the degree we observed. Between 1950 and 1992, additional similar rain events were recorded only twice at the coastal weather stations. In late March, we found slumped roofs over some ringed seal (Phoca hispida) birth lairs and others that had collapsed, probably because of four days of weather only slightly below freezing and heat generated by seals within the lairs. After the rain in April, we found subnivean lairs with melted roofs, and several snowdrifts that had previously contained lairs were completely washed away. Newborn pups were left lying on the bare ice, subject to thermoregulatory stress and vulnerable to significantly increased predation by polar bears (Ursus maritimus) and arctic foxes (Alopex lagopus). If the climate continues to warm in the Arctic, as is predicted, it is likely that rain will be more widespread during early spring. If that occurs, the premature removal of protection offered by subnivean birth lairs may expose young ringed seal pups to high levels of predation, which may negatively affect populations of ringed seals and the polar bears that depend on them for food.

Dynamic cropping strategies for risk management in dry-land farming systems

Low rainfall and soils with low water holding capacity are major features of the Mallee region of south-eastern Australia. To reduce risk related to likely water deficits, many growers adopt a conservative cropping strategy based on low-input cereal crops. This approach has, however, a substantial opportunity cost by missing the potential profit from more intense cereal cropping and high yielding oilseed crops in more favourable seasons. We tested the hypothesis that whole-farm profitability could be enhanced by the adoption of a dynamic cropping strategy shifting from a cereal-only, conservative strategy in dry years, to a more risky strategy involving both cereals and canola in wet years. To test this hypothesis, we used 40-years rainfall series to (1) investigate rainfall features in 11 locations in the Mallee, (2) test the skill of simple rules to predict seasonal rainfall, as developed by local farmers, and (3) calculate whole-farm profit for conservative, risky and dynamic cropping strategies. Rainfall and profit were linked with a whole-farm model that estimates crop yield as a function of seasonal rainfall (i.e. rainfall from April to October) and water-use efficiency. Among locations, annual rainfall ranged from 259 to 358 mm. For each location, two types of seasons were defined: likely wet, when April rain was above the median, and likely dry otherwise. The strength of the association between April and seasonal rain varied widely among sites; it was stronger in locations with more marked rainfall seasonality. Contrasting whole-farm profit responses to cropping strategies were found in locations with annual rainfall below or above a threshold around 300 mm. For wetter locations (annual rain above the threshold), the more risky cropping strategy including canola was generally more profitable than the more conservative strategy. For farms in drier areas, the cereal-based conservative strategy outperformed the more risky strategy in seasons predicted to be dry, but was less profitable in wet seasons. The dynamic cropping strategy had a substantial effect on extreme years, alleviating economic losses associated with the risky strategy in dry seasons, while being able to capture the benefits of more favourable seasons. Analysis of rainfall patterns, development of a rainfall forecasting procedure, and quantification of whole-farm profit in response to cropping strategies, all highlighted the need for decision support tools that account for small-scale variation in rainfall characteristics.

Rain in April

Rain in April

Prediction of SST anomalies of east Pacific Ocean (Nino 3 region) using a statistical model

Average SST anomalies of OCT-DEC months for Nino-3 region are predicted using the following parameters – (i) April rain over Himachal Pradesh, (ii) Darwin pressure change (January–April), (iii) Southern Oscillation Index (Tahiti–Darwin) and (iv) SST anomalies of Nino-3 region in the month of May. Principal component analysis is used to orthogonalise the predictors before using them in the regression equation. The first two principal components, which explain nearly 73% of the variance, are used to fit a regression line. The period 1951–1985 is used as the calibration period for the model and the period 1986–1997 as the verification period for the forecast.

インド域の循環パターンによるエルニーニョ期間中の赤道東太平洋

This study investigates the relationship between circulation anomalies over India during the month of April, and sea surface temperature (SST) anomalies of the eastern Pacific Ocean (Niño 3 region). It is found that rain over northern parts of India and position of 500hPa ridge at 75°E, respectively, have significant correlation coefficients with subsequent SST anomalies of eastern Pacific Ocean (Niño 3 region). Moreover, these relationships are stronger during El Niño years. Since, during El Niño years, peak warming in SST occurs during October-December months, it could well be assessed with the help of these two parameters with the lead time of six months, once occurrence of an El Niño event is indicated by already existing dynamical models. To predict the peak warming during the El Niño years, data of April rain and position of 500hPa April ridge for eleven El Niño years, (1951, 1953, 1957, 1965, 1969, 1972, 1976, 1982, 1987, 1992, 1997) were subjected to the principal component analysis. First principal component was used to predict the average SST anomalies of October-December months through a simple regression equation using cross validation method. The standard deviation of average SST anomalies of October-December months for these eleven years is 0.96, while the root mean square error of the predicted value is 0.52, which is indicative of the good skill of prediction.

The Quezungual System: an indigenous agroforestry system from western Honduras

Information about traditional and unreported agroforestry systems could be useful as a basis for developing adoptable innovations. The Quezungual System, found in the department of Lempira in western Honduras near the border with El Salvador, is one such indigenous system. The distinctive feature of the system is the existence of various naturally-regenerated trees and shrubs that are pollared to a height of approximately 1.5 metres. Farmers also leave taller trees in the fields and these include Cordia alliodora (laurel) and various fruit trees such as Psidium guajava (guayabo). A variety of crops is grown within the System including Zea mays (maize), Sorghum bicolor (sorghum) and Phaseolus vulgaris (beans). Advantages of the System, identified by farmers, include retention of soil moisture, production of fruits and timber, and the fact that plots can be cultivated for longer periods than is normal practice before being left in fallow. One of the prerequisites for the establishment of the System is that farmers abandon the practice of burning their fields prior to the beginning of the rains in April. Those practising the Quezungual System are smallholder farmers living in areas with a scarcity of land. Farmers have customary but not legally- recognised title to their land and many of them have fewer than 2.5 ha of land, much of it on slopes from 5% to 50%. There is growing adoption of the System because of the direct benefits to the smallholder farmer.

Seasonal prevalence of gastrointestinal nematodes in communal land goats from the highveld of Zimbabwe

On six occasions during a 1 year period, goats run on communal pastures by small-scale farmers, were purchased, housed indoors for 3 weeks and autopsied for examination of their gastrointestinal nematode burden. All of the 32 goats examined were infected. The four dominant species, Haemonchus contortus, Trichostrongylus axei, Trichostrongylus colubriformis and Oesophagostomum columbianum, were present in 88–97% of the animals. Three other nematodes, Strongyloides papillosus, Bunostomum spp. and Trichuris spp. occurred respectively in 9%, 3% and 21% of the goats. The total nematode burden was least at the end of the dry season in November and increased gradually through the rainy season to reach a peak at the end of the rains in April. The population of H. contortus followed the same trend as that of the total worm burden. Trichostrongylus colubriformis showed a peak in April and T. axei in June. The fourth stage larvae (L 4) of H. contortus accounted for 0–6.8% of the total H. contortus population during most of the year except in August, when they comprised 46.1% of the burden. It can be concluded that there is a direct relationship between rainfall and intensity of infection with gastrointestinal nematodes.

Rainfall and temperature effects on lentil (Lens culinaris) seed yield in Mediterranean environments

SUMMARYLentil (Lens culinaris Medikus) is a rain-fed crop in North Africa and West Asia whose yields are limited by the amount and distribution of rainfall and winter cold. This study aimed to quantify the effects of climatic variables on lentil seed yields through the fitting of simple empirical models to trial data of two cultivars sown at six sites, 1983–89, representing 31 environments in Syria. The ranges over environments were 152–527 mm for total season rainfall and 1–52 for the number of frost nights. Overall, the total seasonal rainfall accounted for 40·8% of the variance in mean seed yield (1·27 t//ha, S.D. 0·82) with a response of 5·68 kg/ha/mm. A multiple regression model with monthly rainfall from November to May explained 67·6;0% of the variance in mean seed yield. From November to February the response of seed yield to rain was < 10 kg/ha/mm; rain in March, the period of late vegetative growth, made the most important contribution to seed yield. The response to April rain was negative. At Tel Hadya (the most frequently used site), the total seasonal rainfall accounted for 79·8% of the variance in mean seed yield, and the addition of the number of frost nights to the model improved the fit to 92·7%. Winter cold had a smaller effect on yield than rainfall, with no consistent overall effect, but differences over regions. The cultivars contrasted in their responses to drought (78S26002 was superior to ILL4400 at seasonal rainfall levels down to 134 mm) and the number of frost nights at Breda and Tel Hadya (78S26002 was more susceptible to cold than ILL4400). Thus, despite the predominant influence of rainfall on yield, the genetic variability in response to moisture and cold shows the scope for selection under rainfed Mediterranean environments.

Round Iron Markers

30 Round Iron Markers Out tramping fall-plowed fields in April rain, I stepped a fence to neighbor's woods, a grove I hadn't walked before, in memory. Leaves and branches kept me from the muddy floor of a path cut clean between two stands— one young trees, one just scrub, and none worth cutting, save in a winter pinch. So the woodsmen left it all—just worth standing. But then an intuition snagged my cap, like the eyes of a cat or a barn owl watching when you come home late and chore in darkness: It was nothing, nothing but the iron face of wagon wheels, standing by the woodlot gate as if some man in overalls had stopped a bit to rest his team, then got bewildered, lost his place, time, maybe his wife. The wagon stood and waited till the wood had burned away, decayed, leaving four iron wheels, still standing. Far more likely, you know, I know, it was junked by someone's son, too old to fix or be of use, left and not remembered, the iron not worth saving, the wheels only marking where the box had been. Every woodlot has its heap of bottles and tobacco tins in some back corner. Such rusted wheels as these are nothing more, but they mark nothing squarely yet. —William Jolliff 31 ...

Effect of soil environment on infection of subterranean clover by Meloidogyne arenaria

The effect of environmental factors on Meloidogyne arenaria and its infectivity on subterranean clover were investigated both in a naturally infested subterranean clover pasture and under controlled conditions in a pot experiment. In the field, the nematode population was altered by seasonal changes during the sampling periods in 1987 and 1988. The hatching of M. arenaria was determined by the germination of subterranean clover brought about by the opening seasonal rains in April or May. The first generation of M. arenaria in subterranean clover roots appeared to develop and reproduce more rapidly while the soil temperature was still relatively high (>15�C) in May-June and the second generation developed as soil temperature increased between September and November. These findings were consistent with observations from the pot experiment, where M. arenaria gall production and its development and reproduction in both the tap and lateral roots were greater at 20/15�C and 25/20�C than at 15/10�C. In 1987, egg masses of M. arenaria were first observed approximately 6 weeks after the commencement of the growing season, while in 1988 they appeared only after about 15 weeks. This may be attributed to a delay in the opening seasonal rains in 1988 compared with 1987, as well as cooler soil temperatures in 1988. The pF values in the field soils sampled in this study ranged from non-inhibitive to inhibitive suction, with values from 1.8 to 4.8. Greater nematode infection in the tap roots at moisture levels of pF 1.28 and 0.97, but not at 0.71, may be related to better nematode mobility at the higher soil moisture content and its preference for tap roots under more favourable conditions.

A nested grid mesoscale atmospheric chemistry model

A nested grid version of the Regional Acid Deposition Model (RADM) has been developed. The horizontal grid interval size of the nested model is 3 times smaller than that of RADM (80/3 km = 26.7 km). Therefore the nested model is better able to simulate mesoscale atmospheric processes while maintaining consistency with larger‐scale features. The nested model uses dynamic boundary conditions along inflow boundaries which are interpolated from coarse grid model (RADM) results. Since the nesting is one‐way, the outflow boundary conditions are specified to minimize numerical reflections. Three‐day wet deposition amounts of sulfate and nitrate simulated by the nested grid version of RADM as well as the coarse grid version were compared to measurements made by the regional scale network during the Oxidizing and Scavenging Characteristics of April Rains (OSCAR) IV experiment. Both models were able to predict wet depositions of sulfate to within a factor of 2 for over 80% of the sampling sites. Nitrate predictions were slightly worse with just over 70% of the pairs within a factor of two for both models. Although the nested grid model showed no improvement over the coarse grid model in terms of point by point comparisons, it did demonstrate the ability to predict a more realistic range and spatial variability of wet deposition amounts. Plots of predicted deposition fields show that the nested model predicted values similar to the observations in their vicinity more often than did the coarse grid model. Nested model simulations of wet deposition were also compared to measurements made by a high density sampling network over a 110×110km area of northeastern Indiana. Most of the spatial features of the observed distribution were well simulated by the model demonstrating the nested model's ability to resolve processes on scales which are subgrid to the coarse grid model. The predictions of wet depositions by both models were in better agreement with observations than were predictions of precipitation. Since the OSCAR IV experiment was characterized by very efficient washout, the rate of wet deposition was often primarily controlled by the rate of supply of airborne material to the precipitating system rather than aqueous oxidation and precipitation processes. Therefore, errors in precipitation rate had little impact on wet deposition predictions.

Comparison of RADM and OSCAR precipitation chemistry data

This study examines the relationships between predictions of the Regional Acid Deposition Model (RADM) and observed precipitation chemistry patterns associated with frontal storm systems. Three episodes, monitored as part of the Oxidation and Scavenging Characteristics of April Rains (OSCAR) program and referred to as OSCAR I, OSCAR II and OSCAR IV, were analyzed. The temporal and spatial variations of chemical concentrations in rainfall and deposition of SO 4 2−, NO 3 −, H + and NH 4 +, as well as rainfall amounts observed, at up to 36 stations, were compared with the corresponding RADM grid-average predictions. The comparison database is limited by incomplete chemical data for all of the events and some ambiguity regarding the station operation during OSCAR II. The analysis is further complicated by the fact that grid averages are not necessarily representative of point measurements when the measurements are strongly influenced by local phenomena. Quantitative comparisons for each grid-point pair were made using average fractional differences, which are defined as the difference in the observations and predictions divided by the sum of the observations and predictions. For OSCAR IV the SO 4 2− and NO − 3 wet deposition generally were within a factor of 1.1-1.6 agreement, with better than a factor of 1.1 agreement for about one-fifth of the pairs compared. For all of the events, agreement of a factor of two or better generally was associated with good agreement for the ion concentrations in rainfall and the rainfall amounts, in regions of high deposition and at locations less influenced by potential errors in initialization of the RADM simulation. The best agreement for all of the cases was found for SO 4 2− deposition. The accuracy of the precipitation predictions was found to be the major determinant of the deposition agreement. Another suspected factor is the degree to which the grid average rainfall patterns are representative of the point measurements, but the importance of this factor is difficult to establish.

A comparison of breeding and moult cycles and life histories in two tropical starling species: the Blue‐eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long‐tailed Glossy Starling L. purpuropterus

The Blue‐eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long‐tailed Glossy Starling Lamprotornis purpuropterus were investigated in the field and in aviaries at Lake Nakuru National Park, Kenya for seasonality in reproductive activity and moult. The former species was found to be a seasonal breeder which nests after the onset of the heavy rains in April. Although some birds had large gonads prior to the rains in the dry season no nesting occurred. The rains were contemporary with increases in gonadal size and the plasma titres of LH, testosterone (T) in males and estradiol (E2) in females. These hormones are associated with the initiation of breeding activity. As breeding ceased in July and the moult began, the plasma titres again decreased. There was a bimodal breeding pattern which paralleled a change in biotope preference for nesting. Early nests, in the heavy rains, were on the open savanna and later nests were in the acacia forest. Late nesting birds also had delayed peaks in gonadal size, plasma titres of LH, T and E2 and a delayed moult onset. Data on individual captive birds demonstrate that these annual cycles have a distinctly individual character superimposed on the seasonal trends.In Rüppell's Long‐tailed Glossy Starlings no seasonality in breeding was found although the flight feather moult commenced and was completed in all individuals at about the same time. The moult extended over about ten months, so a great deal of breeding‐moult overlap was present. The absence of seasonality in field birds was reflected in the aviary birds, which had no pronounced cycles in the reproductive parameters measured (gonadal size, LH, T and E2 plasma titres). Breeding in field birds was regulated on a pair basis and correlated with increases in duetting. The striking differences in the seasonal organization between this species and Blue‐eared Glossy Starlings were presumably due to the different biotope preferences and social behaviour of the two species.