A test of multiple hypotheses for the function of call sharing in female budgerigars, Melopsittacus undulatus

In many social species group, members share acoustically similar calls. Functional hypotheses have been proposed for call sharing, but previous studies have been limited by an inability to distinguish among these hypotheses. We examined the function of vocal sharing in female budgerigars with a two-part experimental design that allowed us to distinguish between two functional hypotheses. The social association hypothesis proposes that shared calls help animals mediate affiliative and aggressive interactions, while the password hypothesis proposes that shared calls allow animals to distinguish group identity and exclude nonmembers. We also tested the labeling hypothesis, a mechanistic explanation which proposes that shared calls are used to address specific individuals within the sender–receiver relationship. We tested the social association hypothesis by creating four–member flocks of unfamiliar female budgerigars (Melopsittacus undulatus) and then monitoring the birds’ calls, social behaviors, and stress levels via fecal glucocorticoid metabolites. We tested the password hypothesis by moving immigrants into established social groups. To test the labeling hypothesis, we conducted additional recording sessions in which individuals were paired with different group members. The social association hypothesis was supported by the development of multiple shared call types in each cage and a correlation between the number of shared call types and the number of aggressive interactions between pairs of birds. We also found support for calls serving as a labeling mechanism using discriminant function analysis with a permutation procedure. Our results did not support the password hypothesis, as there was no difference in stress or directed behaviors between immigrant and control birds.     

Laser-induced fluorescence of polycyclic aromatic hydrocarbons: an approach to gas standards

Rapid methods are needed to analyse air pollutants such as polycyclic aromatic hydrocarbons (PAHs). Reliable semi-quantitative gas standards were required for the development of a laser-induced fluorescence (LIF) method for polycyclic aromatic hydrocarbon analysis, based on sampling of air onto multi-channel polydimethylsiloxane rubber traps. Easily constructed diffusion tubes provided naphthalene vapour at ~2 ng s⁻¹. A gas chromatographic fraction collection method for loading less volatile PAHs onto the traps from a flame ionization detector outlet was developed and optimized. The accuracy of the method, which can be further optimized, was sufficient for initial LIF screening tests to flag samples exceeding threshold PAH levels for subsequent quantitative GC–MS analysis.     

Potentials and limitations of Coastal Web Atlases

A Coastal Web Atlas (CWA) is a valuable resource for a range of users including coastal managers as it provides easy access to maps, spatial data, coastal information and tools. A trans-Atlantic workshop on “Potentials and Limitations of Coastal Web Atlases”, held in Ireland in July 2006, brought together atlas developers and coastal data experts from Europe and the United States to examine state-of-the-art developments in CWAs and future needs. This paper focuses on workshop outcomes, including what defines a CWA and an overview of international, national, state and regional atlas case studies from both sides of the Atlantic. Results of discussions are presented concerning issues related to design, data, technology and institutional capacity for existing CWAs based on the collective experience of workshop participants. Directions in CWA development and applications since the workshop are also discussed. A major outcome of the workshop was the initiation of an International Coastal Atlas Network. The insights provided give a framework for CWA developers and a useful point of reference for coastal managers and policy makers on atlas potentials and limitations.     

Effects of life history and reproduction on recruitment time lags in reintroductions of rare plants

Reintroductions are important components of conservation and recovery programs for rare plant species, but their long-term success rates are poorly understood. Previous reviews of plant reintroductions focused on short-term (e.g., ≤3 years) survival and flowering of founder individuals rather than on benchmarks of intergenerational persistence, such as seedling recruitment. However, short-term metrics may obscure outcomes because the unique demographic properties of reintroductions, including small size and unstable stage structure, could create lags in population growth. We used time-to-event analysis on a database of unusually well-monitored and long-term (4–28 years) reintroductions of 27 rare plant species to test whether life-history traits and population characteristics of reintroductions create time-lagged responses in seedling recruitment (i.e., recruitment time lags [RTLs]), an important benchmark of success and indicator of persistence in reintroduced populations. Recruitment time lags were highly variable among reintroductions, ranging from <1 to 17 years after installation. Recruitment patterns matched predictions from life-history theory with short-lived species (fast species) exhibiting consistently shorter and less variable RTLs than long-lived species (slow species). Long RTLs occurred in long-lived herbs, especially in grasslands, whereas short RTLs occurred in short-lived subtropical woody plants and annual herbs. Across plant life histories, as reproductive adult abundance increased, RTLs decreased. Highly variable RTLs were observed in species with multiple reintroduction events, suggesting local processes are just as important as life-history strategy in determining reintroduction outcomes. Time lags in restoration outcomes highlight the need to scale success benchmarks in reintroduction monitoring programs with plant life-history strategies and the unique demographic properties of restored populations. Drawing conclusions on the long-term success of plant reintroduction programs is premature given that demographic processes in species with slow life-histories take decades to unfold.     

Application of Static Critical Load Models for Acidity to High Mountain Lakes in Europe

Critical load models for acidityprovide a measure of the sensitivity of surfacewaters to acid deposition, and can be used todetermine critical load exceedance and potentiallong-term harmful effects. Three static models,the Steady-State Water Chemistry model, diatommodel and First-order Acidity Balance model, arehere applied to 11 high mountain lakes in Norway,Scotland, the Alps, the Pyrenees and the Tatras.Between five and seven of the lakes show criticalload exceedance, depending on the model used.Nitrogen as well as sulphur deposition isimportant in causing exceedance. Since soil andvegetation cover are generally sparse, geologyand lake retention time appear to be key factorsin the determination of critical load. Retentionof nitrogen is observed, but it is unclearwhether this occurs within the lake or theterrestrial part of the catchment.     

Factors contributing to radiocaesium variability in upland sheep flocks in west Cumbria (United Kingdom)

Following the Chernobyl accident in 1986, restrictions were placed on the movement and slaughter of sheep within upland areas of the UK because radiocaesium activity concentrations in their meat exceeded 1000 Bq kg(-1) fresh weight. Some farms remain under restriction in 2007. From 1991 to 1993 detailed studies were conducted on three sheep farms within the restricted area of west Cumbria to systematically assess the various parameters which may contribute to the observed variability in radiocaesium activity concentrations within sheep flocks. This paper reports the spatial variation in soil and vegetation activity concentrations across the grazed areas at these farms and determines the influence of grazing behaviour on variability in (137)Cs activity concentrations between individual sheep within the flocks. Together with previously reported results, these new data are used to draw conclusions on the factors determining variability within the three flocks. However, the factors are too site specific to be able to generalise the findings to other farms within the restricted areas of the UK.     

The hunter becomes the hunted: when cleptobiotic insects are captured by their target ants

Here we show that trying to rob prey (cleptobiosis) from a highly specialized predatory ant species is risky. To capture prey, Allomerus decemarticulatus workers build gallery-shaped traps on the stems of their associated myrmecophyte, Hirtella physophora. We wondered whether the frequent presence of immobilized prey on the trap attracted flying cleptoparasites. Nine social wasp species nest in the H. physophora foliage; of the six species studied, only Angiopolybia pallens rob prey from Allomerus colonies. For those H. physophora not sheltering wasps, we noted cleptobiosis by stingless bees (Trigona), social wasps (A. pallens and five Agelaia species), assassin bugs (Reduviidae), and flies. A relationship between the size of the robbers and their rate of capture by ambushing Allomerus workers was established for social wasps; small wasps were easily captured, while the largest never were. Reduviids, which are slow to extract their rostrum from prey, were always captured, while Trigona and flies often escaped. The balance sheet for the ants was positive vis-à-vis the reduviids and four out of the six social wasp species. For the latter, wasps began by cutting up parts of the prey’s abdomen and were captured (or abandoned the prey) before the entire abdomen was retrieved so that the total weight of the captured wasps exceeded that of the prey abdomens. For A. pallens, we show that the number of individuals captured during attempts at cleptobiosis increases with the size of the Allomerus’ prey.