Common goldeneyes adjust maternal effort in relation to prior brood success and not current brood size

Parental investment theory predicts that parental effort should be related to the reproductive value of the current brood. This depends on both the number of young and the survival prospects of each of them. Thus parents may provide more care to larger broods either because of (1) the direct effect of brood size per se on reproductive value (the “brood size” hypothesis) or because (2) past mortality, reflected in current brood size, predicts future mortality of the brood and hence its reproductive value (the “brood success” hypothesis). Earlier studies have not attempted to distinguish between these alternatives. We tested the hypotheses in the precocial, nidifugous common goldeneye Bucephala clangula, a species with uniparental female care. Maternal effort was measured as the time spent by the female in rearing the brood. We found that brood size itself is not associated with maternal effort, but that females modify their maternal effort according to the mortality already experienced by the brood, supporting the prediction of the brood success hypothesis. We also found that brood mortality varied considerably between broods and that previous mortality predicts future mortality within broods, basic assumptions of the brood success hypothesis. Received: 30 January 1996 / Accepted after revision: 27 October 1996     

Genetic mating system and timing of extra-pair fertilizations in the Kentish plover

It is still unclear why females in many bird species pursue extra-pair copulations. Current hypotheses focus mainly on indirect benefits such as obtaining particular good genes for their offspring or maximizing genetic compatibility between themselves and the father of their offspring. Supporting the latter, a recent study of shorebirds suggests that extra-pair matings may function to avoid the negative effects of genetic similarity between mates. Here, we further investigate genetic parentage in the Kentish plover, Charadrius alexandrinus, a shorebird with a highly variable social mating system. DNA fingerprinting revealed that most pairs were genetically monogamous: 7.9% of the broods (7/89) contained extra-pair young, comprising 3.9% of all chicks (9/229). These cases represented, however, three alternative reproductive behaviors: extra-pair paternity, quasi-parasitism (extra-pair maternity) and intraspecific brood parasitism. This is the first study showing the occurrence of all three behaviors in one shorebird species. We also found that extra-pair fertilizations (extra-pair paternity and quasi-parasitism) were more frequent later in the breeding season. There was no consistent relationship between genetic similarity of mates and laying date; the pattern, as well as the degree of genetic similarity, differed among breeding sites within the study population.Communicated by M. Webster     

Food access, brood size and filial cannibalism in the fantail darter, Etheostoma flabellare

We compared the occurrence of filial cannibalism in fed and starved male fantail darters (Etheostoma flabellare). All males in the experiment consumed eggs, and 56% ate all of their eggs. A male's initial body condition did not explain the number of eggs that he ate. Neither did non-fed males eat more eggs than fed males. Fed males were able to maintain better body condition during the experiment, but the change in body condition also depended on the number of eggs eaten. Thus, males who ate more eggs were able to maintain better body condition.The most important determinant of whether or not a male ate all of his eggs was his initial egg number. Males with small egg masses ate all of their eggs whereas males with large egg masses were only partial cannibals. There was, however, no difference in the total number of eggs eaten by total and partial cannibals. We conclude that eggs are only partially eaten for energetic reasons. We also suggest that small egg masses are completely consumed because the costs of caring for a small egg mass may exceed the expected reproductive benefits of a small egg mass. Received: 26 January 1996 / Accepted after revision: 2 November 1996     

Does the great spotted cuckoo choose magpie hosts according to their parenting ability?

When brood parasites are about to lay an egg, they have to decide which nest to parasitize. The best nest in which to lay will depend on the parenting ability of the host. We have studied selection of magpie (Pica pica) hosts by great spotted cuckoos (Clamator glandarius). Great spotted cuckoos preferentially parasitize large host nests. Nest volume in magpies is a good indicator of territory quality, since there is a negative relationship between magpie nest size and breeding date, and timing of breeding in magpies is known to be positively related to territory quality. Moreover, magpies occupying high-quality territories have high breeding success. Therefore, nest size is positively related to the quality of magpies. Parasitized magpie nests were of greater volume than the nearest neighbouring nest not parasitized by the great spotted cuckoo. In order to test whether the great spotted cuckoos might select high-quality magpie hosts, we manipulated pairs of parasitized and non-parasitized nests with identical laying dates and habitats, introducing into each of the nests the same number of parasitic and non-parasitic eggs. The number of fledglings reared (magpie plus great spotted cuckoo chicks) in naturally parasitized nests was higher than in experimentally parasitized nests. Thus, the probability of survival of the parasite chicks increased if cuckoo eggs were laid in the nests of high-quality hosts originally chosen by the parasite.     

生活垃圾分类处理方式的生态效率评价

中国生活垃圾产量大、增速快，若处理方式不当会给环境和社会带来巨大危害，近年来提倡的垃圾分类处理方式是垃圾减量化的关键一环.综合考虑垃圾处理对环境、能源、经济和社会四方面影响，构建适用于垃圾处理的3E+S生态效率评价模型.将垃圾源头分类、末端分类处理方式纳入垃圾处理生命周期中构建4种生活垃圾处理情景.结果表明，混合收运+末端分类的处理情景具有潜在最优生态效率，分类收运+焚烧的处理情景由于源头分类、收运环节更为复杂导致其总环境影响潜值最大，且生命周期成本最高.对比考虑或不考虑社会成本计算得到的生态效率表明，社会成本的加入显著影响生态效率.源头分类是影响生活垃圾分类处理生态效率的敏感性因素，通过降低垃圾源头分类单元过程多余的环境排放和成本或推广使用以末端机械化分类（PGAS）技术为代表的低污染低成本的垃圾分类新技术，都能够提高垃圾处理的生态效率.     

混合多目标遗传算法求解地下水污染修复管理模型

为了提高多目标遗传算法Pareto解的局部最优性,本文将快速非支配遗传算法(NSGAII)与一种迭代式的局部搜索算法(Hill Climber with Step,HCS)相结合,开发了一种新的混合多目标遗传算法NSGAII-HCS.利用CONV1和ZDT6两个经典的多目标优化函数对NSGAII-HCS的性能进行测试,与传统的多目标算法NSGAII相比,CONV1得到的Pareto锋面与真实Pareto最优解锋面的平均距离由5.49减小到1.74,ZDT6则由0.16减小到0,表明NSGAII-HCS在保证解多样性的前提下,能使解接近或收敛到真实的Pareto最优解锋面.最后,将NSGAII-HCS与地下水流模拟软件MODFLOW和溶质运移模拟软件MT3DMS相耦合,并应用到一个理想的二维地下水污染修复管理模型中,结果分析表明该方法可为地下水污染治理提供多样的和收敛的Pareto管理策略,是一种稳定可靠的多目标优化方法.     

Is asynchronous hatching adaptive in herring gulls (Larus argentatus)?

Hatching asynchrony commonly induces a size hierarchy among siblings and the resultant competition for food between siblings can often lead to starvation of the smallest chicks within a brood. We created herring gull (Larus argentatus) broods with varying degrees of hatching synchrony by manipulating the timing of incubation while maintaining the originally laid eggs. The degree of hatching asynchrony affected sibling size hierarchy at the time of hatching of the last-hatched ”c-chick.” In unmanipulated broods, there was no disadvantage of being a c-chick. However, when asynchrony was experimentally increased, we found reduced survival of the c-chick only in the exaggerated asynchronous experimental group. The effects were observable only during the first 10 days of chick life. We recorded no cases of the chicks dying of starvation. Furthermore, behavioral observations indicated that there was no sibling competition, and no selective feeding of larger sibs in the study colony. We propose that the observed lower survival rates of c-chicks in exaggerated asynchronous broods resulted from their lesser motor abilities, affecting their chances of escaping predators. Fledging success for the whole colony was generally high and almost half of all pairs fledged all three chicks, which is indicative of a good feeding environment. We argue that normal hatching asynchrony is a favorable solution in a good feeding environment, but that increased asynchrony reduces breeding success. We do not view asynchrony in the herring gull as an adaptation for brood reduction and propose instead that it may come about because there has been selection for incubation to start before clutch completion. Received: 14 April 1999 / Received in revised form: 20 October 1999 / Accepted: 23 January 2000     

生活垃圾生物预处理后筛分及分选特性试验研究

堆肥化技术作为垃圾预处理方式在国内外已得到了广泛认可.本文通过现场试验,研究了生物预处理对垃圾筛分和分选特性的影响.结果表明,预处理后垃圾含水率降低了7.69%,堆体的体积从275 m~3减少到183 m~3,垃圾的容重从最初的356 kg·m~(-3)增加到470 kg·m~(-3).经过生物预处理,有机物不断被降解.预处理可以提高筛分后筛下物比例,预处理后的筛下物百分比提高了17%.预处理对可回收成分(金属、塑料、纸张、玻璃和布匹等)分选效率都较新鲜垃圾有不同程度的提高,对金属分选效果提高最显著,达到22.01%.本研究表明,生物预处理对垃圾筛分和分选均具有积极的作用,可以提高后期资源回收利用率.     

Host species affects the growth rate of cuckoo (Cuculus canorus) chicks

The cuckoo (Cuculus canorus) is an obligate interspecific brood parasite. When about to lay an egg, the female must decide which nest to parasitise. A high-quality host species should be preferred, to enhance the possibility of producing a viable offspring. In this study, we investigated the effects of two closely related host species, the great reed warbler (Acrocephalus arundinaceus) and the reed warbler (A. scirpaceus) on the growth rate of cuckoo nestlings. We found that cuckoo nestlings raised by the larger host species, the great reed warbler, grew significantly faster and became statistically significantly larger at fledging than nestlings raised by the smaller host, the reed warbler. Our results indicate a qualitative difference between the two host species. The great reed warbler, considered to be the best host, was parasitised at a higher rate than the reed warbler. Received: 2 February 1999 / Received in revised form: 3 September 1999 / Accepted: 18 September 1999     

聚类问题集合论解法初探

本文主要探讨了应用集合论来解聚类问题的方法即集合聚类法,它是在论域上寻找由等价关系所诱导的划分。