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121.
Manipulation of sex differences in parental care 总被引:11,自引:0,他引:11
Summary In a species with biparental care two parents cooperate to provide the appropriate amount of care for the young. Recent theoretical treatments consider the evolutionarily stable investment strategy. Under most conditions, the parental investment of the two partners should be negatively correlated, with the shortfall of one partner being partially compensated for by the other. Previous experimental manipulations of biparental care have involved removal of one partner, yet the response of a widowed bird may differ from that of a mated bird whose partner is doing less than its fair share of parental care. We present the first data involving subtle manipulations of sex differences in parental care where both partners continue to care for the young. This study involves pairs in a nestbox colony of european starlings (Sturnus vulgaris L.) with all brood sizes manipulated to five chicks. Pairs were randomly assigned to three groups: (i) male parental care reduced; (ii) female parental care reduce; and (iii) control pairs. Parental care was manipulated by attaching small weights to the base of a bird's tail feathers. Regardless of sex, nest visitation rate was reduced in the weighted birds with an incomplete compensatory increase by their unweighted partner. Additional parental duties were also considered, including shifts in prey type delivered to the nest, in both weighted birds and their partners. The shift in diet and the overall lower total visitation rate in experimental nests contributed to slower chick growth and lower chick weights than in control nests. The data accord with models suggesting that equality of invesment in biparental species is evolutionarily stable, but reveal new dimensions of parental response that need to be taken into account in theoretical treatments. 相似文献
122.
Populations of Fundulus heteroclitus (L.) at the beginning of a growth season in a New England salt marsh consist of 3 yearly age classes, with the 1-year-old class contributing most of the biomass. Calculation of production rates revealed that the young fish were the most active part of the population and that females were more productive than males. The entire population spent equal amounts of energy in growth and in metabolism. Including the young of the year, we obtained total production of 160 kg dry weight/ha, a value among the highest obtained for natural fish populations. About 5 to 15% of the production is available to predators. Rates of food consumption by F. heteroclitus are high enough to turn over the population of prey relatively often. Popululations of F. heteroclitus are thus capable of exerting an important influence on the abundance and distribution of their prey.Contribution No. 3721 from the Woods Hole Oceanographic Institution. 相似文献
123.
Karl Oliver Kagan Harald Abele Britta Yazdi Bettina Böer Klaus Pintoffl Dave Wright Markus Hoopmann 《黑龙江环境通报》2011,31(13):1229-1233
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125.
University research is pivotal for sustainable development, but to succeed, new ways of conducting research are needed. Only recently has the field of “sustainability and higher education” (SHE) started to deal with the issue. In this paper we define “university research for sustainable development” comprehensively as “all research conducted within the institutional context of a university that contributes to sustainable development”, and propose a set of twenty two preliminary characteristics of this concept. We provide foundational information in particular for various university stakeholders, and those of higher education in general, considering the (re)orientation of research towards sustainable development and offer a beginning of dialogue on the subject, within SHE. 相似文献
126.
R. B. Leidy C. G. Wright H. E. Dupree Jr. 《Journal of environmental science and health. Part. B》2013,48(4):311-319
Abstract Airborne concentrations of diazinon were measured in rooms for 21 days after crack and crevice application. Residue levels were largest in treated rooms (38 μg/m3 ) after application, followed by adjacent (1 μg/m3 ) and upper and lower rooms (ca. 0.4 μg/m ). Low levels of diazinon were detected in all rooms 21 days after application. Small amounts of diazinon (corrected to an 8 min application period) were detected on respirator pads ( 2.6 μg) and waist pads (2.3 μg) worn by the applicator. 相似文献
127.
Contemporary maturation schedules of North Sea haddock, Melanogrammus aeglefinus, differ between spawning centres east and west of the Greenwich meridian. In this study, young-of-the-year haddock from these two sub-stocks were raised under a common environment in order to test whether this sub-stock difference reflected temperature exposure during maturation or an intrinsic (presumed genetic) effect. Maturity–size relationships differed between sub-stocks for the same temperature, indicating an intrinsic component to the contemporary differences now found in the wild. Relative liver mass additionally explained some variation in the maturity–length relationships. Despite inhabiting a thermal regime more favourable for early maturation, west North Sea haddock had the lowest body size and liver mass at maturity for a given temperature. However, historic fishing effort was much higher in the west North Sea, suggesting that contemporary differences may reflect long-term differences in sub-stock mortality. 相似文献
128.
Elizabeth A. Mack Sarah Wrase Joanne Dahme Susan M. Crosby Martha Davis Melody Wright Ravonne Muhammad 《Journal of the American Water Resources Association》2020,56(3):431-449
The ability to pay for water and wastewater services is a growing issue in the developed world. To this point in time, utilities have helped customers grappling with affordability issues using different types of customer assistance programs (CAPs). Income‐based billing approaches differ from CAPs in that bills are structured so as to be affordable for customers at the outset. Recently, the City of Philadelphia implemented an innovative program to work towards resolving the affordability problem in their city using income‐based billing. This tiered assistance program or TAP structures bills for water, wastewater, and stormwater services to program enrollees’ income. Given the innovative nature of the program, this paper describes the rollout of TAP and assesses the impact of the program on customers and utility revenues. The paper closes with a critical assessment of TAP and considerations for utilities evaluating the implementation of similar programs. 相似文献
129.
Sample size planning is one of the most important issues in the design of a study. Simple and accurate sample size formulas for a desired confidence interval width have been developed for many statistical procedures, but a simple and accurate sample size formula for the squared multiple correlation has been a notable exception. Several rule‐of‐thumb sample size recommendations for a multiple regression analysis have been proposed over the years but none are satisfactory. Other approaches have focused on the construction of elaborate tables of sample size requirements, but these tables are both unwieldy and inadequate. We present a simple, accurate, and general method of approximating the sample size requirement for obtaining a squared multiple correlation confidence interval with desired precision. We also present a simple method for approximating the sample size needed to estimate unstandardized regression coefficients with desired precision. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
130.
R.B. Leidy C.G. Wright K. E. MacLeod H.E. Dupree Jr. 《Journal of environmental science and health. Part. B》2013,48(8-9):747-757
Abstract The vertical distribution of diazinon in air was measured for 35 days after a label‐prescribed crack and crevice application. Residue levels were higher at floor level than at chest and ceiling heights on day 0, but levels tended to equalize by 7 days. Concentrations were greater at chest and ceiling levels on days 14 and 21, but were equivalent on days 28 and 35. Residues in the adjacent, upper and lower rooms generally were equivalent at all sampling positions and maximum residues occurred in these rooms, and in three other rooms on the same floor level as the treated room, 3 days after application. Low but measurable residues were found in air samples 35 days after application, which indicates that low concentrations of relatively nonpersistent diazinon will remain within structures protected from direct sunlight and ventilation for several weeks. 相似文献