Comparative responses of ovipositing Anopheles gambiae and Culex quinquefasciatus females to the presence of Culex egg rafts and larvae

Field observations have demonstrated that gravid Anopheles gambiae Giles s.s. (Diptera: Culicidae) are selective in their choice of oviposition sites. For example, immature stages of An. gambiae s.s. are rarely found in water that contains Culex quinquefasciatus Say immatures. The possibility that this may, in part at least, reflect a response by ovipositing An. gambiae s.s. females to volatile signals associated with Culex juveniles was evaluated by testing the response of An. gambiae s.s. females to varying densities of Cx. quinquefasciatus egg rafts and/or larvae in oviposition choice assays. For comparison, the oviposition choices of Cx. quinquefasciatus to conspecific egg rafts and/or larvae were similarly assayed. At a low density of Cx. quinquefasciatus egg rafts (1-15 egg rafts/100 mL water), An. gambiae s.s. females laid more eggs in the treatment water than in the control, with a maximum of twice as many in the treatment water at 5 egg rafts/100 mL water. At higher egg raft densities and in all treatments that included Cx. quinquefasciatus larvae, oviposition decreased significantly in the treatment dishes in a density-dependent manner. As previous studies have indicated, ovipositing Cx. quinquefasciatus females were attracted to and laid egg rafts in dishes containing conspecific egg rafts and, interestingly, also in dishes containing larvae.     

Eavesdropping in crabs: an agency for lady detection

Although conspicuous courtship displays are an effective way of attracting the attention of receptive females, they could provide valuable information to rival males on the location of these females. In fiddler crabs, males that see a receptive female wave their single, greatly enlarged claw in a highly conspicuous courtship display. We test whether other males use this courtship display to alert them to the presence of receptive females that they cannot directly see. We show that male fiddler crabs (Uca mjoebergi) eavesdrop on the courtship displays of nearby males to detect mate-searching females. This allows males to begin waving before a female becomes visible. Furthermore, males appear to adjust their waving according to the information available: eavesdropping males wave 12 times faster than non-courting males but only 1.7 times slower than males in full visual contact with the female.     

Modeling Harvest Intensity of Sooty Shearwater Chicks by Rakiura Māori in New Zealand

Abstract: Cultural evidence suggests that sooty shearwater (Puffinus griseus) chicks have been harvested by Rakiura Māori on islands in southern New Zealand since prehistoric times. Concerns exist that modern harvests may be impacting sooty shearwater abundance. We modeled human-related and ecological determinants of harvest (total no. of individuals harvested) of sooty shearwater chicks on 11 islands and examined the relationship between shearwater abundance and harvesting rates (chicks/hr) and harvester behavior throughout the harvesting season. Models best explaining variation in harvest between harvesting areas (manu), for both the early and late parts of the harvesting season, included harvester-days (included in all models with change in deviance information criteria [ΔDIC], ΔDIC < 8.36 and ΔDIC < 11.5, for the early and late periods, respectively). Other harvest determinants included shearwater density, size of the manu, and number of people helping harvesters (all included in the top 5 models within ΔDIC = 2.25 for the late period). Areas harvested by several families under a common-property harvesting system had higher harvest intensity for their size (24% points higher, 95% credible interval 11–36%) than those managed as an exclusive resource for one family. The slowest harvesters spent more time harvesting but on average only harvested 36% (95% credible interval 15–65%) and 34% (95% credible interval 12–63%) of the harvest taken by the fastest harvesters during the early and late periods, respectively. Our results highlight the possibility of elevated harvest intensity as the population of harvesters increases. However, our models suggested that a corresponding reduction in harvesting rate at low prey densities during the most productive period could potentially regulate harvest intensity. Future research will integrate these results into prospective shearwater demographic models to assess the utility of a range of harvesting strategies in ensuring harvest sustainability.     

Survey Insights into Weighting Environmental Damages: Influence of Context and Group

When one models impact pathways due to stressors that are caused by the provision of product systems, it results in indicators for environmental damages. These indicators are incommensurable and cannot be compared per se. For example, the statistical life years lost for a human population cannot necessarily be compared with the potentially affected fraction of species within an ecosystem. However, some decision makers who use life-cycle assessment (LCA) prefer a single index, because it facilitates interpretation better than a multi-indicator system. This requires a method for aggregating environmental damages of differing types, thereby confronting LCA with a valuation problem.
The article describes a nonmonetary approach to valuation in LCA that incorporates the findings of a survey among LCA practitioners and users. The survey focuses on the weighting of three safeguard subjects for Eco-indicator 99, a damage-oriented impact-assessment method: human health, ecosystem quality, and resources. Of particular interest here is what influence the context provided in the survey (framing) and an individual's characteristics have on his or her weighting of environmental damages. The results indicate that damages on the European level are easier to compare than damages on a micro level. Additionally, although only half of the survey participants could be classified unequivocally into one of three cultural perspectives, each perspective rated the damage categories presented to them significantly differently from the others. Our conclusions were that framing effects need to be more carefully considered in weighting procedures and that weighting preferences vary significantly according to a group's archetypical attitudes.     

Conspecific attraction in a grassland bird, the Baird's Sparrow

ABSTRACT.   Territorial songbirds generally use song to defend territories and attract mates, but conspecific song may also serve as a cue to attract other male songbirds to a breeding site. Although known to occur in some colonial and forest-associated species, only recently have investigators examined conspecific attraction in grassland species. We used a playback experiment to examine the possible role of conspecific attraction for males searching for potentially suitable breeding habitat in a grassland specialist, the Baird's Sparrow ( Ammodramus bairdii ). Experimental playback plots and control plots with similar landscape and vegetation characteristics were established at two sites in North Dakota. Baird's Sparrows colonized three of six experimental plots and none of six control plots. Males on experimental plots established territories adjacent to the playback stations and were sometimes observed counter-singing with the playback of conspecific songs. Vegetation characteristics were similar on all study plots, and did not explain differences in bird density on our treatment plots. Although we found that playback of conspecific songs attracted male Baird's Sparrows to previously unoccupied, potentially suitable habitat, further experiments are needed to examine the importance of conspecific attraction relative to other cues that birds may use, such as vegetation features. The conservation and management implications of conspecific attraction are not completely understood, but the presence of conspecifics should be considered as a potential cue in habitat selection by all species of birds.     

A test of the effect of floral color change on pollination effectiveness using artificial inflorescences visited by bumblebees

Floral color change has been recognized as a pollination strategy, but its relative effectiveness has been evaluated insufficiently with respect to other floral traits. In this study, effects of floral color change on the visitation pattern of bumblebees were empirically assessed using artificial flowers. Four inflorescence types were postulated as strategies of flowering behavior: type 1 has no retention of old flowers, resulting in a small display size; type 2 retains old flowers without nectar production; type 3 retains old flowers with nectar; and type 4 retains color-changed old flowers without nectar. Effects of these treatments varied depending on both the total display size (single versus multiple inflorescences) and the pattern of flower-opening. In the single inflorescence experiment, a large floral display due to the retention of old flowers (types 2–4) enhanced pollinator attraction, and the number of flower visits per stay decreased with color change (type 4), suggesting a decrease in geitonogamous pollination. Type-4 plants also reduced the foraging time of bees in comparison with type-2 plants. In the multiple inflorescence experiment, the retention of old flowers did not contribute to pollinator attraction. When flowering occurred sequentially within inflorescences, type-4 plants successfully decreased the number of visits and the foraging time in comparison with type-2 plants. In contrast, floral color change did not influence the number of visits, and it extended the foraging time when flowering occurred simultaneously within inflorescences but the opening of inflorescences progressed sequentially within a plant. Therefore, the effectiveness of floral color change is highly susceptible to the display size and flowering pattern within plants, and this may limit the versatility of the color change strategy in nature.     

Experimental test on public information use in the colonial Lesser Kestrel

The formation of colonies and the evolution of coloniality have been suggested to be a by-product of the use of public information to select breeding habitats. In this study we performed an experimental test to investigate whether the Lesser Kestrel (Falco naumanni) uses breeding success of conspecifics as a source of public information to select a breeding colony. We considered four potential cues based on reproductive performance of conspecifics in each colony: mean and variance of breeding success measured in both all pairs (TRS, total reproductive success), and only successful pairs (PRS, partial reproductive success). Both mean PRS and mean TRS could be predictive cues of the future reproductive output at a given site, because they varied among colonies and were autocorrelated from one year to the next. To dissociate any relationship between habitat quality and reproductive success we manipulated the mean brood sizes by transferring chicks among ten colonies. In five colonies, all the broods with at least two nestlings were reduced in one chick and in other five colonies all broods were enlarged by one chick. In the following year, we found that the number of adult immigrant kestrels settled at a colony was only explained by mean PRS in the previous year. We also examined the settlement of yearlings, which lack of information on breeding success in previous years. Unlike adult immigrant kestrels, yearlings tended to settle more frequently in those colonies with low mean PRS in the previous year, probably because of the lower pressure for occupation in those colonies. A multiple regression analysis showed that the growth of colonies was positively dependent on the mean PRS in the experimental year, and negatively on the number of predated nests. This study provides a solid support to the hypothesis that colonial species can use mean breeding success of successful pairs as a source of public information to make settlement decisions.