Compensating for the costs of polygyny in hen harriers Circus cyaneus

In polygynous species, the adults are faced with a dilemma during chick rearing. Males must decide how to distribute food between their females and food allocation patterns are often highly unequal. In turn, the females that receive less food from males have to decide how much time to invest in additional hunting. If they spend more time hunting, then they leave their young exposed to weather and predators. However, if they stay at the nest, they increase the risk of their chicks starving. One way that birds may compensate for reduced provisioning is by increasing the size of prey caught. We tested this hypothesis by comparing prey deliveries to nests of hen harriers, Circus cyaneus, with females of different breeding status. As expected, male harriers delivered less food items to the nests of polygynous females, and especially their secondary, or β females. However, both sexes were able to compensate by delivering larger items and there was no difference in the overall mass of food delivered to nests. Moreover, females spent a similar amount of time at the nest, irrespective of status, and there were no overall differences in breeding success. Our results show that polygynous female harriers can compensate for the costs of polygyny, but we suggest that their ability to do so will vary according to the abundance of both large prey and predators.     

Fledgling sex ratio variation and future reproduction probability in Montagu's harrier, Circus pygargus

I studied patterns of sex ratio variation in 543 fledglings from 192 broods of Montagu's harriers Circus pygargus (1992-1998) in Madrid, central Spain, to determine whether offspring sex ratio was adjusted according to variables influencing future reproduction. Fledgling sex ratio variation was related to estimates of food availability during the pre-laying period, with more females produced in years of higher food availability. This variation was related to the probability that females, but not males, were recruited to the breeding population and were recruited at younger ages, if fledged in good food years. Furthermore, the relationship between food and sex ratio was only significant for the first two nestlings in each brood, and only nestlings from first and second ranks benefited from good breeding conditions to advance their age of first breeding. Results presented here differ from other published data for the same species. Geographical variation in observed sex ratio might be explained by differences between populations in factors influencing age of first breeding or other demographic variables.     

Conversion of LDPE into transportation fuels by a two-stage process using Ni/Al-SBA-15 as catalyst

Ni/Al-SBA-15 catalysts with Si/Al atomic ratios within the 20–135 range were prepared by a post synthesis grafting procedure, having nickel contents between 6 and 11 %. The addition of Ni to the Al-SBA-15 support caused a decrease of the BET surface area and pore volume. Additionally, larger Ni particles were attained over the catalysts with higher Si/Al atomic ratios, indicating the existence of some interaction between aluminium species and nickel particles. Ni/Al-SBA-15 catalysts displayed remarkable properties for the preparation of diesel fuels in the hydroreforming of the oils obtained from the LDPE thermal cracking. On increasing the Si/Al atomic ratios of the Ni/Al-SBA-15 catalysts, higher share of light and heavy diesel were attained, the sum reaching a maximum (67.3 %) for Ni/Al-SBA-15(70). This was caused by the higher extent of oligomerization reactions on enhancing the Si/Al atomic ratio. Additionally, around 85–90 % of the starting olefins were successfully hydrogenated and the aromatic content was rather low (below 5 %), without almost any polyaromatic compound (<0.1 %).     

Distributional analysis of regional benefits and cost of air quality control

The methodology and results of an analysis of benefits and costs of air quality control for an urban region in Florida are given. The machinery used considers the spatial distribution of (a) emission sources, (b) the ambient levels resulting from local meteorological conditions and geographic features, and (c) the socioeconomic characteristics of the impacted population groups. This facilitates an examination of the distributional aspects of costs and benefits associated with various control scenarios. With appropriate adaptation and inputs the steps in our analysis should apply to a distributional benefit/cost analyses for any region.     

Selenium volatilization in vegetated agricultural drainage sediment from the San Luis Drain, Central California

The presence of large amounts of Se-laden agricultural drainage sediment in the San Luis Drain, Central California, poses a serious toxic threat to wildlife in the surrounding environment. Effective management of the drainage sediment becomes a practical challenge because the sediment is polluted with high levels of Se, B, and salts. This two-year field study was conducted to identify the best plant species that are salt and B tolerant and that have a superior ability of volatilizing Se from drainage sediment. The drainage sediment was mixed with clean soil, and vegetated with salado alfalfa (Medicago sativa 'salado'), salado grass (Sporobulus airoides 'salado'), saltgrass-turf (Distichlis spp. 'NYPA Turf'), saltgrass-forage (Distichlis spicata (L.) Greene), cordgrass (Spartina patens 'Flageo'), Leucaenia (Leucaena leucocephola), elephant grass (Pennistum purpureum), or wild type-Brassica (Brassica spp.). Results show that elephant grass produced the greatest amount of biomass and accumulated highest concentrations of B. Highest concentrations of Se, S, and Cl were observed in wild-type Brassica. Biogenic volatilization of Se by plants and soil microbes was greater in summer. Among the treatments, the mean daily rates of Se volatilization (microg Se m(-2)d(-1)) were wild-type Brassica (39) > saltgrass-turf (31) > cordgrass (27) > saltgrass forage (24) > elephant grass (22) > salado grass (21) > leucaenia (19) > salado alfalfa (14) > irrigated bare soil (11) > non-irrigated bare soil (6). Overall, rates of Se volatilization in drainage sediment were relatively low due to high levels of sulfate. To manage Se in drainage sediment by phytoremediation, the biological volatilization process needs to be enhanced substantially under field conditions.     

A novel statistical method for classifying habitat generalists and specialists

We develop a novel statistical approach for classifying generalists and specialists in two distinct habitats. Using a multinomial model based on estimated species relative abundance in two habitats, our method minimizes bias due to differences in sampling intensities between two habitat types as well as bias due to insufficient sampling within each habitat. The method permits a robust statistical classification of habitat specialists and generalists, without excluding rare species a priori. Based on a user-defined specialization threshold, the model classifies species into one of four groups: (1) generalist; (2) habitat A specialist; (3) habitat B specialist; and (4) too rare to classify with confidence. We illustrate our multinomial classification method using two contrasting data sets: (1) bird abundance in woodland and heath habitats in southeastern Australia and (2) tree abundance in second-growth (SG) and old-growth (OG) rain forests in the Caribbean lowlands of northeastern Costa Rica. We evaluate the multinomial model in detail for the tree data set. Our results for birds were highly concordant with a previous nonstatistical classification, but our method classified a higher fraction (57.7%) of bird species with statistical confidence. Based on a conservative specialization threshold and adjustment for multiple comparisons, 64.4% of tree species in the full sample were too rare to classify with confidence. Among the species classified, OG specialists constituted the largest class (40.6%), followed by generalist tree species (36.7%) and SG specialists (22.7%). The multinomial model was more sensitive than indicator value analysis or abundance-based phi coefficient indices in detecting habitat specialists and also detects generalists statistically. Classification of specialists and generalists based on rarefied subsamples was highly consistent with classification based on the full sample, even for sampling percentages as low as 20%. Major advantages of the new method are (1) its ability to distinguish habitat generalists (species with no significant habitat affinity) from species that are simply too rare to classify and (2) applicability to a single representative sample or a single pooled set of representative samples from each of two habitat types. The method as currently developed can be applied to no more than two habitats at a time.