Benefits of large broods by higher chick survival and better territories in a precocial shorebird

When reproductive success is constant in one breeding phase, different tactics that increase variation in reproductive success among individuals may evolve in other phases. For instance, in shorebirds, which usually have a limited clutch size of four eggs, variation in reproductive tactics among individuals is expected either before egg-laying (e.g. diverse mating systems) or after hatching of the young (e.g. diverse parental care). In this paper, I studied the pied avocet (Recurvirostra avosetta), a shorebird with a modal clutch size of four eggs, to test whether post-hatch chick adoption as an alternative tactic can be linked to increased variation in annual reproductive success. When predation was high, naturally adopting pairs produced more filial fledglings than did pairs not adopting chicks and not losing chicks to adoption. The number of filial fledglings increased with the number of adopted young, possibly through diluting the chances of predation on filial young. Experimental chick addition did not lead to more fledged young due to low brood integrity as shown by the frequent loss of chicks from some experimental broods. When predation was low, larger broods occupied feeding territories with higher prey abundance than smaller broods, possibly due to their dominance over smaller ones. Pairs that lost chicks to adoption (donors) fledged as many filial young in their broods as did non-adopters/non-donors, whereas the total number of donors’ filial fledglings, including those raised in adopting broods, approached that of adopters. These findings show, for the first time, that post-hatch alternative reproductive tactics can lead to variation in annual reproductive success and to higher success for some pairs even in species where past adaptations limit variation in reproductive success in a certain phase of reproduction.     

Clustering of aerosols in atmospheric turbulent flow

A mechanism of formation of small-scale inhomogeneities in spatial distributions of aerosols and droplets associated with clustering instability in the atmospheric turbulent flow is discussed. The particle clustering is a consequence of a spontaneous breakdown of their homogeneous space distribution due to the clustering instability, and is caused by a combined effect of the particle inertia and a finite correlation time of the turbulent velocity field. In this paper a theoretical approach proposed in Elperin et al. (2002) Phys Rev E 66:036302 is further developed and applied to investigate the mechanisms of formation of small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The theory of the particle clustering instability is extended to the case when the particle Stokes time is larger than the Kolmogorov time scale, but is much smaller than the correlation time at the integral scale of turbulence. We determined the criterion of the clustering instability for the Stokes number larger than 1. We discussed applications of the analyzed effects to the dynamics of aerosols and droplets in the atmospheric turbulent flow.     

Hull fouling on commercial ships as a vector of macroalgal introduction

Hull fouling is thought to have been the vector of introduction for many algal species. We studied ships arriving at a Mediterranean harbour to clarify the present role of commercial cargo shipping in algal introductions. A total of 31 macroalgal taxa were identified from 22 sampled hulls. The majority of records (58%) were of species with a known cosmopolitan geographical distribution. Due to a prevalence of cosmopolitan species and a high turnover of fouling communities, species composition of assemblages did not appear to be influenced by the area of origin, length of ship or age of coating. In the light of the present results, hull fouling on standard trading commercial vessels does not seem to pose a significant risk for new macroalgal species introductions. However, a high proportion of non-cosmopolitan species found on a ship with non-toxic coating may modify this assessment, especially in the light of the increasing use of such coatings and the potential future changes in shipping routes.     

The effect of ambient temperature on forager sound production and thoracic temperature in the stingless bee, <Emphasis Type="Italic">Melipona panamica</Emphasis>

Foragers of the stingless bees genus Melipona may produce intranidal sounds that are correlated with food location and quality. In this study, we provide the first detailed analysis of pulsed sounds produced by Melipona panamica foragers while feeding on a carbohydrate food source. We trained foragers to a 2.5-M sucrose feeder under normal, ambient temperature (23–33°C) and lower temperature (11–25°C) conditions. We recorded forager sounds under both conditions and tested the effect of temperature of the thorax, feeder plate, and air on sound temporal characteristics. Forager energetic expenditure and the number of pulses per visit were significantly higher in the cold condition than in the normal condition. Foragers spent a longer time at the feeder under the cold condition than during the normal condition. Interpulse durations were significantly shorter in the cold condition than in the normal condition and became progressively and significantly shorter at the end of each performance. Thus, pulse production increased before departure. Foragers increased their thoracic temperatures above ambient at all experimental air temperatures. Under chilled conditions, foragers had a significantly greater difference between thorax temperature and ambient air temperature than under normal conditions. Foragers must achieve a minimum flight muscle temperature before take-off, and thus forager sounds may be linked to muscle warm-up.     

Differences in acoustic directionality among vocalizations of the male red-winged blackbird (<Emphasis Type="Italic">Agelaius pheoniceus</Emphasis>) are related to function in communication

Studies of animal acoustic communication have found that the frequency and temporal structure of acoustic signals can be shaped by selection for efficient communication. The directionality of acoustic radiation may also be adapted for communication, but we know relatively little about how directionality varies with signal function, sender morphology, and the environment in which the sound is transmitted. We tested the hypothesis that the directionality of a vocalization is adapted to its function in communication. This hypothesis predicts that vocalizations that are directed to multiple conspecifics (e.g., advertisements and alarms) will be relatively omnidirectional because this will maximize the number of neighbors and mates that receive the signal, and that vocalizations directed to particular individuals will be relatively directional because this will maximize detection of the signal by the targeted receiver and minimize eavesdropping. To test these predictions, we measured the directionality and amplitude of red-winged blackbird (Agelaius pheoniceus) vocalizations in the field by recording vocalizations simultaneously on eight calibrated microphones encircling the bird. We found significant variation in directionality among vocalizations. Supporting our predictions, we found that the most omnidirectional vocalizations were those used to alert conspecifics to danger, and the most directional vocalizations are those used during courtship and solicitation of copulation, when the costs of eavesdropping are likely to be high. These results suggest that the directionality of red-winged blackbird vocalizations is shaped by selection for effective communication. This study is the first to provide statistical support for the hypothesis that directionality is related to the function of a signal in communication.     

Fish assemblages in seagrass beds are influenced by the proximity of mangrove forests

Mangrove forests and seagrass beds frequently occur as adjacent habitats in the temperate waters of southeastern Australia. At low tide when fish cannot occupy mangroves they might utilise adjacent habitats, including seagrass. We first sampled small fish from seagrass beds close to and far from mangroves in the Pittwater estuary, NSW, Australia. Seagrass beds close to mangroves had a greater density of fish species than beds far from mangroves (close: mean 16.0 species net⁻¹, SE 1.0; far: 13.2, 1.3; P < 0.05). In particular, juvenile fish were in greater densities near to than far from mangroves (close: 5.3, 0.4; far: 3.1, 0.4; P < 0.05). We then sampled the mangrove forests during the high tide and seagrass beds during the low tide, in beds along a continuum of distances from mangroves. Multivariate analysis showed that fish assemblages differed with distance from mangroves, and the differences were attributed to the composition of the fish assemblage (i.e. presence/absence of fish species), not the abundances of individual species. In particular, fish that utilise mangrove forests at high tide were found in greater species densities and species richness in seagrass nearer to mangroves. A negative relationship was found between the density of mangrove-utilising fish species and the distance of the bed from mangroves (R ² = 0.37, P < 0.05). This confirms the important connectivity between mangroves and seagrass for fish in temperate Australian waters.     

Reproduction in short-beaked common dolphins (<Emphasis Type="Italic">Delphinus delphis</Emphasis>) from the western North Atlantic

A single population of short-beaked common dolphins (Delphinus delphis Linnaeus) occurs in the western North Atlantic from Florida to Newfoundland. Dolphins killed in a swordfish driftnet fishery between 1989 and 1998 provided samples for the present study. These were combined with additional observations from carcasses collected from stranding programs. Samples were examined from 74 female and 161 male short-beaked common dolphins. A highly significant male bias in the sex ratio of both the bycatch and stranding samples suggests that sex-based habitat partitioning or school segregation occurs in this population. Age was estimated from decalcified thin sections of teeth and testis and ovarian samples were examined both macro- and microscopically. Analyses showed that reproduction was both seasonal and synchronized. Females reached sexual maturation at approximately age eight; males matured at 9.5 years. Conception occurred during July and August (mean day 24 July). Gestation was estimated to last just under a year, so most females gave birth during July and August (mean day 15 July). Annual pregnancy rate was estimated to be between 25 and 33%. Males undergo a fivefold seasonal increase in testes mass and a twofold increase in seminiferous tubule diameter. Peak sperm production potential was observed in July. At the end of the breeding season testis size and activity decreased after August. Male dolphins in this population are hypothesized to engage in some form of sperm competition.     

Sex difference in signature whistle production of free-ranging bottlenose dolphins,Tursiops truncates

Signature whistles of 42 free-ranging bottle-nose dophin calves were compared to those of their mothers. Humans judged their similarity by inspection of spectrograms. There was a sex difference in the tendency of calves to produce whistles similar to or different from those of their mothers; most female calves produced whistles that were different from those of their mothers, whereas male calves were more likely to produce whistles that were similar to those of their mothers. Because matrilineally related females associate together and use signature whistles to establish and/or maintain contact with their calves, there may be a selective pressure for females to produce whistles that are distinct from those of their mothers. There may be fewer constraints governing whistle development in males, with the result that some males produce whistles similar to those of their mothers and others do not.     

Charakterisierung von Holzasche aus Biomassefernheizwerken

Analyses of ashes from wood chips and bark combustion and research work about possibilities of utilization of these ashes showed that in general a mixture of bottom ash and cyclon fly-ash in the ratio as they occur in the plant can be used as a fertilizer and liming material. An important question is whether mineral impurities (sand, earth, stones) in the biomass are responsible for slagging on the grate (by lowering the melting point) because sintered and slagged ash with a particle size larger than 2 cm has to be sieved or milled before utilized. Furthermore, the influence of these impurities on the homogeneity of wood ash is important for taking and preparing samples for analysis. Usually, the occurring ash fractions in biomass district heating plants can only be volumetrically measured. In order to determine the actual mass flow and to proportion the ash-amounts for fertilization properly, it is necessary to know the bulk densities of the different ash fractions in dependence on the particle size and the biomass used. Moreover, the knowledge of the surface properties of fly-ash particles enables to evaluate the influencing variables on the process of heavy metal deposition from the flue gas to the fly-ash particles. This information represents the basis for a fractionated desublimation/condensation of heavy metals. The aim is to concentrate them in the filter fly-ash, because this smallest and finest ash fraction is cut off from the ash cycle and is disposed of. Conforming to these open questions, ashes from biomass district heating plants were examined. The facts and findings obtained represent the basis for technological measures in order to improve a closed cycle economy with wood ash.     

Hotspots of Epiphytic Lichen Diversity in Two Young Managed Forests

Understanding within-stand variation in diversity of epiphytes will provide an improved basis for producing timber while conserving biological diversity. Two 80-ha, 50–year–old managed stands of conifers were surveyed to locate 0.4 ha putative "diversity" plots, the areas appearing most diverse in lichen epiphytes. These plots were generally located in areas made heterogeneous by canopy gaps, wolf trees (trees with large-diameter lower branches), and old-growth remnant trees. "Matrix" plots, in contrast, were chosen at random from the remaining, more homogenous forest. Diversity plots hosted from 25% to 40% more epiphytic lichen species than matrix plots in both stands. The strongest within-stand gradients in species composition were correlated with percentage of plot occupied by gaps and wolf trees. Percentage of the plot in gaps was correlated with species richness (r = 0.79). In the more structurally diverse stand, diversity and abundance of nitrogen-fixing "cyanolichens" were correlated with percentage of the plot occupied by gaps (0.5 < r < 0.9), and alectorioid lichens were correlated with percentage of the plot occupied by old-growth remnant trees (0.5 < r < 0.6). In the stand with more homogenous structure, percentage of the plot under gaps was correlated with regionally common species that were otherwise absent or sparse in the matrix. Protecting gaps, hardwoods, wolf trees, and old-growth remnant trees during thinning or other partial cutting is likely to promote the majority of epiphytic macrolichens in young conifer forests. Because these features are easily recognized on aerial photos and on the ground by land managers, it is practical to manage for forest structures that would promote lichen diversity.