Ventral-aspect radar cross sections and polarization patterns of insects at X band and their relation to size and form

A data set of ventral-aspect insect radar cross-sections (RCSs) and polarization patterns, measured at X band (9.4 GHz, linear polarization) in laboratory rigs, has been collated from a number of sources. The data have been analysed to identify relationships between RCS parameters (one representing size and two the polarization-pattern shape) and the insects’ masses and morphological dimensions and forms. An improved mass-estimation relationship, with appropriate asymptotes for very small and very large insects, is presented. This relationship draws only on the RCS size parameter and it is shown that incorporating one or both of the RCS shape parameters provides little additional benefit. Small insects have polarization-pattern shapes that fall within a relatively limited region of the range of parameter values allowed by electromagnetic scattering theory. Larger insects have shapes that extend beyond this region, following a broad trajectory as size and mass increases; at masses above ~0.6 g, the pattern becomes ‘perpendicular’, with maxima when the E-field is orthogonal to the body axis rather than parallel to it. RCS shape can be used to infer morphological form for small insects (<80 mg), but not for larger ones. These results are consistent with observations from X-band vertical-beam entomological radars and provide a basis for identification, at least to broad taxon classes, of the targets detected by such radars

Radar, Insect Population Ecology, and Pest Management

Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives

Observations of movement dynamics of flying insects using high resolution lidar

Insects are fundamental to ecosystem functioning and biodiversity, yet the study of insect movement, dispersal and activity patterns remains a challenge. Here we present results from a novel high resolution laser-radar (lidar) system for quantifying flying insect abundance recorded during one summer night in Sweden. We compare lidar recordings with data from a light trap deployed alongside the lidar. A total of 22808 insect were recorded, and the relative temporal quantities measured matched the quantities recorded with the light trap within a radius of 5 m. Lidar records showed that small insects (wing size 2.5 mm 2 in cross-section) were most abundant near the lidar beam before 22:00 and then moved towards the light trap between 22:00 and 23:30. We could distinguish three insect clusters based on morphology and found that two contained insects predominantly recorded above the field in the evening, whereas the third was formed by insects near the forest at around 21:30. Together our results demonstrate the capability of lidar for distinguishing different types of insect during flight and quantifying their movements

The nocturnal flight calls of migratory songbirds: interspecific variation in the “zeep” complex and intraspecific variation across North America

The nocturnal flight calls of birds are short vocalizations, produced primarily during migration. Although these calls offer a unique opportunity for studying avian migration, there has been little research into many aspects of these calls, such as the species-specificity of the calls of closely related taxa, or variation in calls associated with age, sex, or geography. The objective of my thesis research was to investigate acoustic variation within the flight calls of songbirds to expand our understanding of these calls and their application in migration monitoring. I recorded the flight calls of birds held for banding as well as birds actively flying during their nocturnal movements. In my first data chapter, I investigated whether the nocturnal flight calls of nine warbler species (i.e. the “zeep” species-group) exhibited acoustic differences. Analysis of the acoustic properties of flight calls of these species revealed significant differences in call structure between species, including five species that were notably different from the others in one or more acoustic properties. My results revealed that flight calls could be assigned to the correct species more often (73%) than expected by chance (36%), although the classification was not perfect. Therefore, acoustic variation in the flight calls of the “zeep” complex can be used to identify more species than previously thought. In my second data chapter, I explored intraspecific variation in flight calls. I found no evidence of sex-based or age-based variation in three species, and no evidence of geographic variation in two species. Although I found geographic variation in the calls of Dark-eyed Juncos, there was no consistent pattern on an east-west axis. Together, these results provided very little evidence for variation in flight calls with sex or age and limited evidence for geographic variation. Consequently, flight calls may be used to identify species (or species-groups) but not to identify sex, age, or geographic origin. My research serves to enhance the capabilities of nocturnal flight call detections for monitoring migratory birds while improving our understanding of drivers of variation in these calls

Behavioral responses of Brazilian free-tailed bats (\u3ci\u3eTadarida brasiliensis\u3c/i\u3e) to noctuid moth migrations

Animal migrations involve significant movement of biomass across landscapes and are likely to have cascading effects on animal and plant communities. However, most studies on migration address the behavior and ecology of single taxa, such as birds or insects. Few consider more than one trophic level or predator/prey interaction within the overall migration context. I studied the migration ecology of noctuid moths and of Brazilian free-tailed bats in Texas. Noctuid moth migrations during the 2010-2012 fall seasons were driven significantly by weather at the regional and local levels. Bats also responded to the same weather patterns, with changes in body mass and bat flight activity linked to increased northerly wind after cold front passage. Many of the behavioral and physiological changes in bats were more likely due to their own migratory cycles, rather than in direct response to the local availability of migratory moths in the study area. Noctuid moths are destructive agricultural pests affecting crops on a continental scale, and the bats offer significant pest control ecosystem services. Since the system is driven by weather, understanding the system is important because it is likely to be affected by climate change

Simulation of the Radar Cross Section of a Noctuid Moth

Electromagnetic modelling may be used as a tool for understanding the radar cross section (RCS) of volant animals. Here, we examine this emerging method in detail and delve deeper into the specifics of the modelling process for a single noctuid moth, with the hope of illuminating the importance of different aspects of the process by varying the morphometric and compositional properties of the model. This was accomplished by creating a high-fidelity three-dimensional insect model by micro-CT scanning a gold-palladium-coated insect. Electromagnetic simulations of the insect model were conducted by applying different morphological and compositional configurations using the WiPL-D Pro 3D Electromagnetic Solver. The simulation results show that high-resolution modelling of insects has advantages compared to the simple ellipsoidal models used in previous studies. We find that the inclusion of wings and separating the composition of the body, wings, and legs and antennae have an impact on the resulting RCS of the specimen. Such modifications to the RCS are missed when a prolate spheroid model is used and should not be ignored in future studies. Finally, this methodology has been shown to be useful in exploring the changes in the RCS that result from variations in specimen size. As such, utilising this methodology further for more species will improve the ability to quantitatively interpret aeroecological observations of weather surveillance radars and special-purpose entomological radars

Methods for estimating long-distance dispersal

Long-distance dispersal (LDD) includes events in which propagules arrive, but do not necessarily establish, at a site far removed from their origin. Although important in a variety of ecological contexts, the system-specific nature of LDD makes far removed difficult to quantify, partly, but not exclusively, because of inherent uncertainty typically involved with the highly stochastic LDD processes. We critically review the main methods employed in studies of dispersal, in order to facilitate the evaluation of their pertinence to specific aspects of LDD research. Using a novel classification framework, we identify six main methodological groups: biogeographical; Eulerian and Lagrangian movement/redistributional; short-term and long-term genetic analyses; and modeling. We briefly discuss the strengths and weaknesses of the most promising methods available for estimation of LDD, illustrating them with examples from current studies. The rarity of LDD events will continue to make collecting, analyzing, and interpreting the necessary data difficult, and a simple and comprehensive definition of LDD will remain elusive. However, considerable advances have been made in some methodological areas, such as miniaturization of tracking devices, elaboration of stable isotope and genetic analyses, and refinement of mechanistic models. Combinations of methods are increasingly used to provide improved insight on LDD from multiple angles. However, human activities substantially increase the variety of long-distance transport avenues, making the estimation of LDD even more challenging

New Frontiers in the Application of Stable Isotopes to Ecological and Ecophysiological Research

This Research Topic aims to present cutting-edge applications of stable isotope methods to animal and plant ecology and ecophysiology.https://digitalcommons.odu.edu/biology_books/1020/thumbnail.jp