Bird Functional Diversity in Agroecosystems and Secondary Forests of the Tropical Andes

Agricultural systems have increased in extension and intensity worldwide, altering vertebrate functional diversity, ecosystem functioning, and ecosystemic services. However, the effects of open monoculture crops on bird functional diversity remain little explored, particularly in highly biodiverse regions such as the tropical Andes. We aim to assess the functional diversity differences of bird guilds between monoculture crops (coffee, cocoa, and citrus) and secondary forests. We use four functional diversity indices (Rao Q, Functional Richness, Functional Evenness, and Functional Divergence) related to relevant morphological, life history, and behavioral traits. We find significant differences in functional diversity between agroecosystem and forest habitats. Particularly, bird functional diversity is quite homogeneous among crop types. Functional traits related to locomotion (body weight, wing-chord length, and tail length), nest type (closed), and foraging strata (canopy and understory) are dominant at the agroecosystems. The bird assemblages found at the agroecosystems are more homogeneous in terms of functional diversity than those found at the secondary forests, as a result of crop structure and management. We recommend promoting more diverse agroecosystems to enhance bird functional diversity and reduce their effects on biodiversity.

A revision of bird skin preparation aimed at improving the scientific value of ornithological collections

The methods used to preserve bird skins in museums have a potentially crucial impact on the feasibility and use of these specimens as a source of biological knowledge, although this subject is rarely broached. Study skins of birds are usually prepared with folded wings and straight legs to facilitate storage in the collection; yet, this method can hamper the measurement and examination of certain important features such as wing-feather moult. To make consultation easier for ornithologists, alternative preparation methods such as the splitting of wings and tarsi from the rest of the animal have been proposed by curators. Our aim was to study whether or not preparing bird specimens with spread limbs makes consultation simpler. First, we used two different methods to prepare two specimens each of two common European passerine species: (1) ‘traditional’ (folded wings and straight tarsi) and (2) ‘spread’ (limbs spread on one side of the body). Then, we asked 22 experienced ornithologists to identify moult limits and take three biometric measurements (wing chord, length of the third primary feather and tarsus length) from all four specimens. Subsequently, we asked which preparation method they preferred for obtaining data. The ‘spread’ preparation was preferred for moult, third primary feather length and tarsus length, whilst the ‘traditional’ preparation was preferred for wing chord. Data obtained from the folded and spread preparations were very highly repeatable within each method but only moderately to highly repeatable between methods. One of the handicaps with the ‘spread’ preparation is the increase in storage space required, a factor that should be taken into account before it is employed. Nevertheless, this specimen preparation technique can greatly facilitate consultation and therefore improve the scientific value of ornithological collections.

Design and development of a vortex ring generator to study the impact of the ring as a gust

ABSTRACTWe present a simple method to generate discrete aerodynamic gust under controlled laboratory condition in the form of a vortex ring which, unlike conventional methods of perturbation, is well studied and highly controllable. We characterized the flow properties of the vortex ring using flow visualization and novel light bead method. Reynolds number of the vortex ring, based on its average propagation velocity and nozzle exit diameter, was 16000. We demonstrate this method by studying the impact of head-on gust on freely flying soldier flies, Reynolds number of which, based on its wingtip velocity and mean wing chord, was 1100. We also present simple theoretical models to characterize the vortex ring based on generating conditions. The device can also be used to generate continuous gust in any direction and can be applied, in general, to study the gust response of natural fliers and swimmers, man-made micro aerial vehicles and aquatic plant lives.

Body Condition in Birds in Two Landscapes of the Upper Magdalena Valley, Colombia

The body condition (BC) is the sum of factors such as the state of energy reserves, the degree of health and the physiological wear of an individual. Despite its importance and the existence of a wide range of methodologies to measure it, in the Neotropic there are few works that value this variable in contrast to environmental conditions. The aim of this study was to analyze the BC during the years 2012-2013 of 13 bird species in two intervened landscapes in the tropical dry forest, located in the north of Tolima and the southwest of Huila in the region of the upper Magdalena Valley (UVM). The BC of species was assessed using the scaled mass index (SMI), using morphometric data such as wing chord, tarsal length and body mass. Significant differences were found in the SMI between landscapes and climatic seasons in the species Formicivora grisea, Saltator striatipectus, Sporophila schistacea and Basileuterus rufifrons. It was concluded that environmental variables evaluated affect the BC of some species but not the avifauna in general, mainly due to the effect of these variables on the availability of resources, the necessary energy spending to obtain them and the sensitivity of species to environmental changes.

Global instability in the onset of transonic-wing buffet

Global stability analysis is used to analyse the onset of transonic buffet on infinite swept and unswept wings. This high-Reynolds-number flow is governed by the unsteady Reynolds averaged Navier–Stokes equations. The analysis generalizes earlier studies focused on two-dimensional airfoils. For the unswept wing, results show spanwise-periodic stationary modes in addition to the earlier-observed oscillatory mode. The oscillatory mode is nominally two-dimensional with a spanwise wavelength greater than ten wing chords. The stationary modes of instability exist over two bands of spanwise wavelengths centred around an intermediate wavelength of one wing chord, and around a short wavelength of one tenth of a wing chord. The intermediate-wavelength modes have a flow structure characteristic of airfoil buffeting modes, concentrated at the shock and in the shear layer downstream of the shock. The short-wavelength modes are only concentrated in the shear layer downstream of the shock. These stationary modes can lead to spanwise-periodic flow structures for the unswept wing. For the swept wing, these stationary modes become unsteady travelling modes and contribute to the more complex buffeting-flow structures observed on swept wings as compared with unswept wings. The spanwise-wavelength bands of the travelling modes translate to different frequencies, resulting in a broad-banded unsteady response for the swept wing. For a $30^{\circ }$ swept wing, the frequencies associated with the intermediate-wavelength modes are approximately 10 times higher than the swept-wing generalization of the long-wavelength oscillatory mode, and approximately 6 times higher than the long-wavelength mode for the unswept wing. These instability characteristics are in good agreement with experimental observations.

Drivers of variation in migration behavior for a linked population of long-distance migratory passerine

Despite advances in tracking technologies, migration strategies remain poorly studied for many small-bodied passerines. Understanding variation within a migration strategy is important as variation impacts a population’s resilience to environmental change. Timing, pathway, and stopovers vary based on intrinsic and extrinsic factors that impact individual migration decisions and capacity. Here, we studied drivers of variation in migration across a linked population of Golden-winged Warbler (Vermivora chrysoptera) using data from 37 light-level geolocators. We tested if behaviors vary in response to extrinsic factors: season, year, and proximity to a large geographic barrier—the Gulf of Mexico—and intrinsic factors: age and wing chord. Spring migration was nearly twice as fast as fall migration, with tightly correlated arrival and departure dates that were consistent among years, in contrast to no correlation or consistency in fall. This aligns with predictions for selection to minimize time spent migrating in spring and a relaxation of that pressure in fall. Twenty-nine birds staged for multiple days (mean: 7.5, SE: 0.6) in stopover habitats before crossing the Gulf of Mexico in spring, but 6 individuals overwintering closer to the Gulf coast forewent the stopover and completed migration 8 days faster. These findings suggest birds capable of crossing the Gulf without a stopover may experience a selective advantage by minimizing total migration time. After crossing the Gulf, individuals reduced travel speed and stopover duration, indicating constraints on movement differ before and after the barrier. Wing chord, but not age, positively predicted the total distance and duration of migration, and neither varied with timing, suggesting migration distance impacts morphology, but strategies do not vary with age. Ultimately, we find undescribed stopover locations south of the Gulf are important for most of the population, while high variation in migration behaviors suggest potential resilience to changing environmental conditions. Causantes de variación en el comportamiento migratorio para una población vinculada de un paseriforme migratorio de larga distancia

Wing-Propeller Interaction

Paper describes the effect of the distributed electric propulsion system (DEP) on the aerodynamic characteristics of the airplane wing. Using CFD simulation is described the influence of the wake of the propeller on the wing for various ratios of the propeller diameter to the wing chord. Unlike the normal case of wing-propeller interaction, periodic boundary conditions are used, i.e. a rectangular wing with infinite span with propellers installed periodically its span is considered. A wind tunnel experiment will be used to verify the calculations. Propeller thrust is set to compensate for airplane drag in horizontal flight, i.e. equal to the wing segment drag, which is increased by the corresponding part of the expected drag of other parts of the airplane. The increase of the drag was determined by the aerodynamic design of a generic airplane with DEP. The benefit of the work are the input data usable for the conceptual design of the airplane wing with DEP.

Exploitation of a Multifunctional Twistable Wing Trailing-Edge for Performance Improvement of a Turboprop 90-Seats Regional Aircraft

Modern transport aircraft wings have reached near-peak levels of energy-efficiency and there is still margin for further relevant improvements. A promising strategy for improving aircraft efficiency is to change the shape of the aircraft wing in flight in order to maximize its aerodynamic performance under all operative conditions. In the present work, this has been developed in the framework of the Clean Sky 2 (REG-IADP) European research project, where the authors focused on the design of a multifunctional twistable trailing-edge for a Natural Laminar Flow (NLF) wing. A multifunctional wing trailing-edge is used to improve aircraft performance during climb and off-design cruise conditions in response to variations in speed, altitude and other flight parameters. The investigation domain of the novel full-scale device covers 5.15 m along the wing span and the 10% of the local wing chord. Concerning the wing trailing-edge, the preliminary structural and kinematic design process of the actuation system is completely addressed: three rotary brushless motors (placed in root, central and tip sections) are required to activate the inner mechanisms enabling different trailing-edge morphing modes. The structural layout of the thin-walled closed-section composite trailing-edge represents a promising concept, meeting both the conflicting requirements of load-carrying capability and shape adaptivity. Actuation system performances and aeroelastic deformations, considering both operative aerodynamic and limit load conditions, prove the potential of the proposed structural concept to be energy efficient and lightweight for real aircraft implementation. Finally, the performance assessment of the outer natural laminar flow (NLF) wing retrofitted with the multifunctional trailing-edge is performed by high-fidelity aerodynamic analyses. For such an NLF wing, this device can improve airplane aerodynamic efficiency during high speed climb conditions.

Experimental study of a pitching and plunging wing

Purpose The complex flow behavior over an oscillating aerodynamic body, e.g. a helicopter rotor blade, a rotating wind turbine blade or the wing of a maneuvering airplane involves combinations of pitching and plunging motions. As the parameters of the problem (Re, St and phase difference between these two motions) vary, a quasi-steady analysis fails to provide realistic results for the aerodynamic response of the moving body, whereas this study aims to provide reliable experimental data. Design/methodology/approach In the present study, a pitching and plunging mechanism was designed and built in a subsonic closed-circuit wind tunnel as well as a rectangular aluminum wing of a 2:1 aspect-ratio with a NACA64-418 airfoil, used in wind turbine blades. To measure the pressure distribution along the wing chord, a number of fast responding transducers were embedded into the mid span wing surface. Simultaneous pressure measurements were conducted along the wing chord for the Reynolds number of 0.85 × 106 for both steady and unsteady cases (pitching and plunging). A flow visualization technique was used to detect the flow separation line under steady conditions. Findings Elevated pressure fluctuations coincide with the flow separation line having been detected through surface flow visualization and flattened pressure distributions appear downstream of the flow separation line. Closed hysteresis loops of the lift coefficient versus angle of attack were measured for combined pitching and plunging motions. Practical implications The experimental data can be used for improvement of unsteady fluid mechanics problem solvers. Originality/value In the present study, a new installation was built allowing the aerodynamic study of oscillating wings performing pitching and plunging motions with prescribed frequencies and phase lags between the two motions. The experimental data can be used for improvement of computational fluid dynamics codes in case that the examined aerodynamic body is oscillating.