Sex-role reversal in willow tit nest defence

Summary The roles of sexes in the nest defence behavior of monogamous willow tit (Parus montanus) were studied near Oulu, northern Finland, in 1988–1990. The relative roles of the sexes changed during the breeding cycle: females defended their nests more vigorously before hatching and males defended more after hatching. This sexual asymmetry was studied by means of the cost/benefit model of optimal parental investment (PI). Because of the monogamous breeding system, sexual differences in future benefits were not a likely explanation for the asymmetry. This was also supported by preliminary results of DNA-fingerprinting analyses. Behavioral observations — sex-role reversal, high correlation between the mates, and equal variations in male and female behavior — indicated the same. In the beginning of the breeding cycle, higher female defence was related to renesting potential. The extra costs of renesting are considerably higher for females than for males, and therefore, females appeared to benefit more than males in keeping the first clutch alive while renesting was still possible. Such a female strategy was possible in this northern population, since the time for renesting was rather short and never lasted beyond the hatching of the first nests. After this point, the male can only invest in the present clutch. By the end of the breeding cycle, increased defence of the nest by males may be a consequence of males being larger and/or in better condition than females. Therefore, in the latter half of the breeding cycle, the sexual differences in nest defence did not indicate any sexual difference in PI. The asynchronous arrival of the parents at the nest also affected individual responses, indicating that defending the nest is a dynamic process.     

Analysis of radiation hazards to personnel on marine platforms

The large number of radio frequency (RF) transmitters employed in modern marine platforms requires that they operate in mutual coexistence while posing no danger to operators and equipment despite the limited available physical space. A key to the successful system integration is the control of the electromagnetic environment on the ships’ topsides, which might pose radiation hazards (RADHAZ) to personnel (HERP). HERP are caused by transmitter antenna installations that generate intentional EM radiation in excess of the safe levels in zones of personnel activity. Radiation safety to personnel is achieved when the average radiation power density is below the permissible exposure limits (PEL) for HERP at locations of personnel activity and medical equipment operation. This paper describes the analysis tools and techniques for the evaluation of HERP on marine platforms. The same approaches could be employed in the analysis of land site antenna deployment scenarios.     

Sex-specific nest defense in house sparrows (Passer domesticus) varies with badge size of males

According to indicator models of sexual selection, females can benefit from choosing males with above average epigamic traits, but empirical evidence for such benefits is scarce. Here, we report results from an experiment with 29 pairs of house sparrows (Passer domesticus) where the intensity of nest defense against a mounted mustelid predator was related to the size of the black throat and breast patch (“badge”) in males. Using principal components analysis (PCA), original response variables of both sexes were reduced to two factors: “Approach” to the predator and “Distant warning”. “Approach”, the more risky behavior, increased from small- through medium- to large-badged males and decreased in their females. Since large-badged males have a higher certainty of paternity (i.e. greater benefits from defense) and may be older and more experienced (i.e. incur lower costs), the most likely explanation for male defense intensity increasing with badge size is an improving benefit/cost ratio. The resulting optimal response of their females and evolutionarily stable participation in joint parental care is illustrated by a graphical model. It shows that females would, indeed, benefit directly from choosing large-badged males. This, however, is no proof of a direct evolutionary tie between badge size and paternal behavior, as assumed by indicator models of sexual selection. It may simply represent a spurious relationship, originating from the correlation of badge size and defense with confidence of paternity. Received: 22 September 1997 / Accepted after revision: 3 November 1997     

环境类高职院校工学结合人才培养模式构建

立足当前环境类高等职业教育人才培养中存在的突出问题,以＂以人为本＂、＂需求导向＂、＂特色品牌＂、＂工学结合＂为原则,提出了环境类高职院校应在构建人才培养＂三个平台、四个模块＂的基础上,突出实践能力培养,实施工学结合的人才培养模式。     

The Benefits of Nest Relocation Extend Far Beyond Recruitment: A Rejoinder to Mrosovsky

Individual sea turtle nests have an extremely low probability of producting adult turtles; thus the practice of moving nests away from the ocean (where they will not be inundated by seawater) is a questionable conservation strategy. Recently in Environmental Management, Mrosovosky used the repeatability of nesting female turtles to place their eggs in certain locations to infer that some females may consistently nest in areas which will be flooded, lowering the chance that any eggs will hatch. This information was used to hypothesize that saving “doomed” sea turtle nests may then alter the genetic composition of the population, ultimately resulting in turtles that nest in poor habitats. Here I question Mrosovosky’s argument by focusing on several weaknesses inherent in the original article, namely that at present there is no evidence to suggest that nest-site selection is a heritable trait with an underlying genetic basis.     

Optimal timing of comb construction by honeybee (Apis mellifera) colonies: a dynamic programming model and experimental tests

Honeybee colonies, like organisms, should exhibit optimal design in their temporal pattern of resource allocation to somatic structures. A vital colony structure is the comb which stores honey for overwinter survival. However, the timing of comb construction poses a dilemma to a colony attempting to maximize its honey reserves. On the one hand, plenty of empty comb is needed for efficient exploitation of temporally unpredictable flower blooms. On the other hand, because comb is made from energetically expensive wax, its construction too early or in excessive amounts will reduce the amount of honey available for winter thermoregulation and brood-rearing. A dynamic optimization model concludes that colonies should add new comb only when they have filled their old comb with food and brood above a threshold level. The threshold increases with time until, at the end of the season, building is never an optimal behavior. The temporal pattern of construction predicted by the model – pulses of building coincident with periods of nectar intake and comb fullness – matches that seen in an actual colony observed over the course of an entire foraging season. When nectar sources are rich but temporally clumped, the model also predicts that bees should be sensitive to nectar intake, employing much higher thresholds on days when nectar is not available than on days when it is. Even under poorer and more dispersed nectar regimes, little fitness cost is paid by colonies replacing the optimal strategy with a simpler rule of thumb calling for new construction only when two conditions are met: (1) a fullness threshold has been exceeded, and (2) nectar is currently being collected. Experiments demonstrate that colonies do in fact use such a rule of thumb to control the onset of construction. However, once they have begun building, the bees continue as long as nectar collection persists, regardless of changes in comb fullness. Thus the onset and duration of comb-building bouts appear to be under partially independent control. Received: 30 October 1998 / Received in revised form: 14 December 1998 / Accepted: 16 January 1999     

A nesting association between semi-colonial Bullock's orioles and yellow-billed magpies: evidence for the predator protection hypothesis

Mixed-species nesting associations have been reported for many birds. However, few studies have shown that one species specifically chooses to nest close to another in order to obtain a direct benefit and only two studies have managed to adequately test the predator protection hypothesis for such associations. Here we demonstrate a nesting association between Bullock's orioles (Icterus galbula bullockii) and yellow-billed magpies (Pica nuttalli). The evidence indicates that this is an active association in which, given a choice of suitable habitat areas in which to nest, orioles choose those areas that contain magpie nests. Oriole nests associated with magpie nests have a significantly reduced predation rate compared to those without associated magpie nests. This suggests that orioles prefer to nest near to magpies and that this preference has evolved due to the protection provided by neighbouring magpies. The nesting association results in the clumping of oriole nests around magpie nests, and therefore provides a possible explanation for the semi-colonial nature of Bullock's orioles. Received: 23 November 1998 / Received in revised form: 25 May 1999 / Accepted: 30 May 1999     

Air Emissions Assessment from Offshore Oil Activities in Sonda de Campeche, Mexico

Air emission data from offshore oil platforms, gas and oil processing installations and contribution of marine activities at the Sonda de Campeche, located at the Gulf of Mexico, were compiled and integrated to facilitate the study of long range transport of pollutants into the region. From this important region, roughly 76% of the total Mexican oil and gas production is obtained. It was estimated that the total air emissions of all contaminants are approximately 821,000 tons per year. Hydrocarbons are the largest pollutant emissions with 277,590 tons per year, generated during flaring activities, and SOx in second place with 185,907 tons per year. Marine and aviation activities contribute with less than 2% of total emissions. Mass of pollutants emitted per barrel of petroleum produced calculated in this work, are in the range reported by similar oil companies.     

Development of an integrated chemical,biological and ecological approach for impact assessment of Mediterranean offshore gas platforms

The pressure for more energy demand is a strong driver for the construction of offshore oil and gas platforms. This also applies to the Adriatic Sea where, since 1960, several gas fields have been commissioned. The continuous expansion of the gas industry may potentially have detrimental effects on marine communities. This may become particularly clear in such a peculiar semi-enclosed basin as the Adriatic Sea, which contains ecosystems that are subject to intensive anthropic pressures, such as unsustainable fishing and inputs of environmental pollutants. To date, still scant information is available on the environmental effects of gas platforms. Thus, to comply with the national Italian legislation and to support the development of protocols for the monitoring of offshore activities, multidisciplinary studies have been conducted and performed by CNR-ISMAR in cooperation with some private and public research institutes. A multidisciplinary approach based on chemical, biological and ecological investigations was performed to evaluate both the water column and the sediment quality near a gas platform. The overall results indicate moderate effects of platform-related environmental stress.     

Efficiency and regulation of recruitment during colony emigration by the ant Temnothorax curvispinosus

Recruitment helps insect societies by bringing individuals to places where work needs to be done, but it also imposes energetic and opportunity costs. The net effect depends both on recruitment efficiency and on the ease with which insects can find work sites on their own. This study examined both of these factors for colony emigration by the ant Temnothorax curvispinosus. Emigrations were organized by a corps of active ants who transported the rest of the colony. These active ants either found new sites independently or followed tandem runs led by successful scouts. Although most tandem runs broke apart before reaching their target, even lost followers found the new site faster than did unguided searchers. When the new site was near the old nest, tandem runs were rare and summoned only a small proportion of the transporter corps. When the new site was instead distant and inconspicuous, tandem runs were common and brought roughly one third of the transporters. This pattern likely results from the quorum rule used by individual scouts to decide when to switch from tandem runs to transports. By monitoring how many nestmates have already found the nest, the ants ensure that the costs of recruitment are born only when necessary.