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151.
Ultraviolet (UV) reflectance of the plumage is common in birds and plays an important role in sexual signalling. Recently,
it has been proposed that birds are able to modify plumage UV reflectance by the application of uropygial gland secretion.
Based on a survey of the optical properties of this secretion from 51 species belonging to 12 avian orders, we show that two
main types of uropygial secretions exist, one predominantly found in passerines and one in non-passerines, both reducing relative
UV reflectance of a white background (Teflon™ tape). We quantified how each type of secretion (exemplified by blue tit and
mallard) affected feather UV reflectance. Both secretions reduced overall brightness and relative UV reflectance of white
mallard feathers but hardly affected the reflectance of UV/blue blue tit crown feathers. According to models of avian colour
vision, changes in reflectance due to application of the secretion were at or below the discrimination threshold of most birds.
We conclude that the uropygial secretion is unlikely to play a major role in modifying plumage UV reflectance. However, the
optical properties of the uropygial secretion may have been selected to interfere as little as possible with visual signaling
through plumage reflectance.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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A. Peters K. Delhey W. Goymann B. Kempenaers 《Behavioral ecology and sociobiology》2006,59(5):666-673
The proximate basis of sexual traits can suggest mechanisms maintaining honesty in signalling. A central role hereby has been
attributed to testosterone, although its importance for brightly coloured plumage has been questioned. We determined circulating
testosterone levels in male blue tits captured at the start of breeding and demonstrated an age-dependent relationship between
testosterone and male crown UV/blue coloration. In yearling males, testosterone increases with increasing ornamentation (higher
UV chroma, higher chroma, more UV-shifted hue), whereas in older males, this relationship is negative, with less UV-ornamented
males having higher testosterone. This pattern is robust since it occurred in 2 years, before and after egg laying, and in
males sampled during the day and during the night, despite a tenfold difference in testosterone levels. Since more UV-ornamented
young males gain higher within-pair paternity, while less UV-ornamented older males achieve more extra-pair matings, the results
imply that higher testosterone is associated with reproductive success and attractiveness in both age classes. We hypothesise
that this relationship could result from causal effects of testosterone on coloration or through associations with behaviour
and suggest ways to test these hypotheses. Our results caution against premature dismissal of a potential role for testosterone
in maintaining honesty of plumage signals. 相似文献
156.
Brominated dibenzo-p-dioxin and dibenzofuran (BDD/BDF) isomers, specifically having from one to three halogens located in the 2,3,7,8-substituent positions, that are [13C]-labeled for use as analytical internal standards in mass spectrometric methods are not yet commercially available. Based upon the current availability of [13C]-labeled dibenzo-p-dioxin and dibenzofuran (DD/DF) precursors, we have developed a simple and efficient synthetic procedure which produces brominated congeners that are predominantly substituted in the 2,3,7, and 8-positions. The gas/solid reaction of vaporized precursor and surface-supported iron (III) bromide occurs rapidly (seconds) at temperatures ≥ 240°C and can provide total product yields in the range of 30 to 50 mole % for initial precursor amounts between 1 μg and 10 mg. In this paper we shall describe the utility of this approach to produce 5 μg quantities of [13C12]-2,7-dibromodibenzo-p-dioxin (27-DBDD) and [13C12]-2,8-dibromodibenzo-p-dioxin (28-DBDD). 相似文献
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Jenkins RA Ilgner RH Tomkins BA Peters DW 《Journal of the Air & Waste Management Association (1995)》2004,54(2):229-241
Protocols have been developed and applied for the generation of aerosols that are likely to be comparable to those encountered in field settings for the calibration of easily transportable/portable real-time particle monitors. Aerosols generated were simulated environmental tobacco smoke, cedar wood smoke, cooking oil fumes, and propane stove particles. The time-integrated responses of three nephelometers and a monitor for particle-bound polynuclear aromatic hydrocarbons (PAH) were compared with gravimetric respirable suspended particulate matter (RSP) in a controlled-atmosphere chamber. In general, the monitor responses increased linearly with increasing mass concentration. However, the two monitors that reported mass per volume concentrations tended to overreport the actual RSP concentrations by factors up to 4.4. The real-time PAH monitor did not respond to cooking oil fumes, indicative of little PAH being present in the aerosol. One of the monitors that has been used in a variety of studies reported in the literature (DustTrak) was collocated with gravimetric RSP samplers in several hospitality venues in the Louisville, KY, area. Field studies indicated that the units overreported actual RSP concentrations by factors of 2.6-3.1, depending on whether the sampling was conducted in the nonsmoking or smoking sections of the facilities. 相似文献
158.
Connectivity of Streams and Wetlands to Downstream Waters: An Integrated Systems Framework 总被引:1,自引:0,他引:1
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Scott G. Leibowitz Parker J. Wigington Jr. Kate A. Schofield Laurie C. Alexander Melanie K. Vanderhoof Heather E. Golden 《Journal of the American Water Resources Association》2018,54(2):298-322
Interest in connectivity has increased in the aquatic sciences, partly because of its relevance to the Clean Water Act. This paper has two objectives: (1) provide a framework to understand hydrological, chemical, and biological connectivity, focusing on how headwater streams and wetlands connect to and contribute to rivers; and (2) briefly review methods to quantify hydrological and chemical connectivity. Streams and wetlands affect river structure and function by altering material and biological fluxes to the river; this depends on two factors: (1) functions within streams and wetlands that affect material fluxes; and (2) connectivity (or isolation) from streams and wetlands to rivers that allows (or prevents) material transport between systems. Connectivity can be described in terms of frequency, magnitude, duration, timing, and rate of change. It results from physical characteristics of a system, e.g., climate, soils, geology, topography, and the spatial distribution of aquatic components. Biological connectivity is also affected by traits and behavior of the biota. Connectivity can be altered by human impacts, often in complex ways. Because of variability in these factors, connectivity is not constant but varies over time and space. Connectivity can be quantified with field‐based methods, modeling, and remote sensing. Further studies using these methods are needed to classify and quantify connectivity of aquatic ecosystems and to understand how impacts affect connectivity. 相似文献
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