Geographic Range Fragmentation and Abundance in Neotropical Migratory Birds

Populations of neotropical migrant landbirds have experienced significant declines in recent years. We investigated potential consequences of these declines by examining the relationship between abundance and fragmentation of geographic ranges of species on the North American breeding grounds. We estimated areograpbic fragmentation using the box dimension of a species' geographic range and demographic fragmentation using the fractal dimension of the semivariance function calculated from samples of population abundance across species' geographic ranges. We found a negative relationship between average abundance and demographic fragmentation for neotropical migrants, but not for residents. We also showed that demographic fragmentation and areographic fragmentation are inversely related for residents, but not for neotropical migrants. These results imply that neotropical migrants may be more sensitive to extinction than are residents.     

Testosterone treatment suppresses paternal care in superb fairy-wrens, Malurus cyaneus, despite their concurrent investment in courtship

Courtship displays and paternal care in male birds are generally thought to be mutually exclusive, because testosterone, necessary for stimulation of sexual behaviours, suppresses paternal behaviours. Superb fairy-wrens, Malurus cyaneus, are unusual in that males concurrently engage in courtship and paternal care. Fairy-wrens live in stable socially monogamous pairs with 0-4 subordinate male helpers. Both helper and dominant males provide care whenever it is required but continue courtship throughout the period of care as most fertilisations are extra-group and females are multi-brooded. To examine the role of testosterone in this trade-off, we compared testosterone levels in males of different social status, while they had dependent nestlings, and determined the effect of testosterone treatment on provisioning rates of pairs. Testosterone levels were lower in subordinate helpers, although these do not provide more paternal care than dominant males. Conversely, testosterone levels were similar in dominant males with or without helpers, although as the number of helpers increases males invest substantially less in nestling care and more in extra-group courtship. Although testosterone levels are high, irrespective of paternal duties, experimental testosterone treatment of males resulted in a large (65%) reduction in nestling feeding rates. Surprisingly, there was no indication that females compensated for this reduction in provisioning, suggesting that females might assume a constant male contribution to offspring care. We conclude that during nestling provisioning, male fairy-wrens maintain testosterone at an individual level that does not interfere with parental duties, while allowing high investment in extra-group courtship.     

Brood sex ratio and male UV ornamentation in blue tits (<Emphasis Type="Italic">Cyanistes caeruleus</Emphasis>): correlational evidence and an experimental test

Sex-allocation theory predicts that females paired to attractive males should bias the brood sex ratio towards male offspring, as these would inherit the attractiveness of their father. We studied sex allocation based on male ornamentation in blue tits. Brood sex ratios varied with male UV coloration in an age-dependent manner. For juvenile males, the proportion of sons increased with increasing UV ornamentation, which is in agreement with previous findings from a Swedish population. However, the relationship between UV ornamentation and brood sex ratio was reversed for adult males, with females paired to less UV-ornamented adult males producing more sons. This pattern fits with the observation that, in our population, less UV-ornamented adult males sire the majority of extra-pair young. To test the causality of the association between brood sex ratio and male coloration, we experimentally manipulated crown colour largely within the natural range. We created two groups of males: one with higher and one with lower UV reflectance, UV(+) and UV(−), respectively. Contrary to our expectations, there was no significant treatment effect. However, in UV(−), but not UV(+) males, the proportion of sons was negatively correlated with male coloration before manipulation. This suggests that the UV(−) treatment caused males that were more UV ornamented to decline more in attractiveness, as shown in a similar experiment in Sweden. However, given that correlational patterns differ between these populations, similarities in experimental results should not be taken as evidence for consistent patterns of adaptive sex allocation in this species.     

Evaluation of multisectional and two-section particulate matter photochemical grid models in the Western United States

Version 4.10s of the comprehensive air-quality model with extensions (CAMx) photochemical grid model has been developed, which includes two options for representing particulate matter (PM) size distribution: (1) a two-section representation that consists of fine (PM2.5) and coarse (PM2.5-10) modes that has no interactions between the sections and assumes all of the secondary PM is fine; and (2) a multisectional representation that divides the PM size distribution into N sections (e.g., N = 10) and simulates the mass transfer between sections because of coagulation, accumulation, evaporation, and other processes. The model was applied to Southern California using the two-section and multisection representation of PM size distribution, and we found that allowing secondary PM to grow into the coarse mode had a substantial effect on PM concentration estimates. CAMx was then applied to the Western United States for the 1996 annual period with a 36-km grid resolution using both the two-section and multisection PM representation. The Community Multiscale Air Quality (CMAQ) and Regional Modeling for Aerosol and Deposition (REMSAD) models were also applied to the 1996 annual period. Similar model performance was exhibited by the four models across the Interagency Monitoring of Protected Visual Environments (IMPROVE) and Clean Air Status and Trends Network monitoring networks. All four of the models exhibited fairly low annual bias for secondary PM sulfate and nitrate but with a winter overestimation and summer underestimation bias. The CAMx multisectional model estimated that coarse mode secondary sulfate and nitrate typically contribute <10% of the total sulfate and nitrate when averaged across the more rural IMPROVE monitoring network.     

Perspectives of a large scale environmental survey for chlorinated dioiins: water analyses

During 1983 and 1984, The Dow Chemical Company conducted a study to determine the extent of dioxin contamination at its Midland, Michigan plant and the surrounding area. The primary objectives of this study were to identify, rank order, and when possible quantify potential sources of dioxins to the environment and also to determine the extent of contamination in areas affected by the Dow facility. Early in the study, it was estimated that approximately 0.6g/year of 2378-TCDD was being emitted in 2.5 × 10¹⁰L of wastewater effluent. Data will describe observed sources of TCDD (both current and historical), environmental levels, existing water treatment methods, control measures taken, and future improvements on the water system to reduce TCDD in the effluent.     

Geometric variability and surface finish of weld zones in Yb:YAG laser welded advanced high strength steels

Laser welding is used for joining advanced high strength steels (AHSS) to improve formability and performance. In this paper, the geometric variability observed in the fusion zones and heat affected zones of several combinations of AHSS (different types, coatings and thicknesses), which were butt welded using a Trumpf TRUDISK 6000^® Yb:YAG laser beam, is presented. The surface texture parameters such as roughness and waviness of laser welds were also measured and correlated with geometric variability. Results indicate that although high quality welds with minimal defects can be obtained using the Yb:YAG laser welding process, there is considerable variation in both the shape and the dimensions of weld zones. The variability increased with an increase in thickness differentials between the sheets being welded. Analysis of the top of the weld surfaces also suggested that aluminum coating on USIBOR samples contributes significantly to increased roughness. An increase in laser power coupled with corresponding increase in welding speed did not impact variability. A fair correlation between the surface roughness and weld region variability exists, although this needs further study.