Avian Forelimb Muscles and Nonsteady Flight: Can Birds Fly Without Using the Muscles in their Wings?

Intensity patterns of electromyographic (EMG) signals from selected muscles of the wing were studied during different modes of flight in trained Rock doves (Columba livia). Shoulder muscles exhibited a stereotypic pattern producing maximal EMG intensity during the deceleration phases of the upstroke and the downstroke, whereas the muscles of the brachium and antebrachium acted primarily as joint stabilizers during level flapping flight. During nonsteady flight (e.g. takeoff, landing, vertical ascending flight), the distal forelimb muscles exhibited maximal EMG intensity; their primary function appears to be associated with changing the camber and planform of the wing during rapid oscillation. During steady flight, an automatic linkage system consisting of forelimb skeletal elements and ligamentous attachments is thought to permit proper excursion of the wing as a result of forces generated solely by proximal muscles of the wing. To test this hypothesis, the medianoulnaris and radialis nerves were cut in five animals, thus eliminating the contribution of the forearm muscles, and flight tests were performed. Even though forearm muscles were incapable of contracting, the birds were capable of sustained level flapping flight. They were unable to take off independently or perform controlled landings

Wing-Assisted Incline Running and the Evolution of Flight

Flapping wings of galliform birds are routinely used to produce aerodynamic forces oriented toward the substrate to enhance hindlimb traction. Here, I document this behavior in natural and laboratory settings. Adult birds fully capable of aerial flight preferentially employ wing-assisted incline running (WAIR), rather than flying, to reach elevated refuges (such as cliffs, trees, and boulders). From the day of hatching and before attaining sustained aerial flight, developing ground birds use WAIR to enhance their locomotor performance through improved foot traction, ultimately permitting vertical running. WAIR provides insight from behaviors observable in living birds into the possible role of incipient wings in feathered theropod dinosaurs and offers a previously unstudied explanation for the evolution of avian flight

What Use is Half a Wing in the Ecology and Evolution of Birds?

The use of incipient wings during ontogeny in living birds reveals not only the function of these developing forelimbs in growing birds’ survival but also the possible employment of protowings during transitional stages in the evolution of flight. When startled, juvenile galliform birds attempt aerial flight even though their wings are not fully developed. They also flap their incipient wings when they run up precipitous inclines, a behavior we have described as wing-assisted incline running (WAIR), and when they launch from elevated structures. The functional benefit of beating these protowings has only recently been evaluated. We report the first ontogenetic aerial flight performance for any bird using a ground bird, the chukar partridge (Alectoris chukar), as a model species. We provide additional ontogenetic data on WAIR, a recently described locomotor mode in which fully or even partially developed flapping forelimbs are recruited to increase hindlimb traction and escape performance. We argue that avian ancestors may have used WAIR as an evolutionary transition from bipedal locomotion to flapping flight

Life-History Correlates of Taxonomic Diversity

One of the most pervasive, nonrandom evolutionary patterns is extreme domination of a taxon by one subtaxon or only a few subtaxa. Domination refers to taxonomic diversity and the fraction of the taxon that is classified in the most diverse subtaxon. We attempt to explain how subtaxa come to dominate their phyletic counterparts by examining correlations between taxonomic diversity and life history traits such as age of first reproduction, longevity, fecundity and partitioning of reproduction, and resource availability in a variety of vertebrate, invertebrate, and plant groups. Regardless of taxonomic group or rank, the number of taxa within an assemblage, or the school of taxonomy employed, diverse taxa were characterized by short generation time (early age of first reproduction and short life—span) and the ability to contact many resources (high mobility and high resource availability). We suggest that the intrinsic character of short generation time increases diversity because it promotes speciation and reduces extinction. Extrinsic factors such as resource availability and environmental complexity and variability may have a secondary influence on diversity by constraining or enhancing speciation for taxa with short generation times. Read More: http://www.esajournals.org/doi/abs/10.2307/293718

Electrometry Using Coherent Exchange Oscillations in a Singlet-Triplet-Qubit

Two level systems that can be reliably controlled and measured hold promise in both metrology and as qubits for quantum information science (QIS). When prepared in a superposition of two states and allowed to evolve freely, the state of the system precesses with a frequency proportional to the splitting between the states. In QIS,this precession forms the basis for universal control of the qubit,and in metrology the frequency of the precession provides a sensitive measurement of the splitting. However, on a timescale of the coherence time, $T_2$, the qubit loses its quantum information due to interactions with its noisy environment, causing qubit oscillations to decay and setting a limit on the fidelity of quantum control and the precision of qubit-based measurements. Understanding how the qubit couples to its environment and the dynamics of the noise in the environment are therefore key to effective QIS experiments and metrology. Here we show measurements of the level splitting and dephasing due to voltage noise of a GaAs singlet-triplet qubit during exchange oscillations. Using free evolution and Hahn echo experiments we probe the low frequency and high frequency environmental fluctuations, respectively. The measured fluctuations at high frequencies are small, allowing the qubit to be used as a charge sensor with a sensitivity of $2 \times 10^{-8} e/\sqrt{\mathrm{Hz}}$, two orders of magnitude better than the quantum limit for an RF single electron transistor (RF-SET). We find that the dephasing is due to non-Markovian voltage fluctuations in both regimes and exhibits an unexpected temperature dependence. Based on these measurements we provide recommendations for improving $T_2$ in future experiments, allowing for higher fidelity operations and improved charge sensitivity

Martian terrains

Terrain studies of candidate landing sites for a future rover/sample-return mission to Mars are being conducted to evaluate the geologic and trafficability aspects of each site. An optimum site should have geologic units of widely diverse ages and chemical compositions occurring in close enough proximity and in smooth enough terrain so that a roving vehicle of limited traverse ability (+ or - 100 km) could collect representative samples. In FY 1986, geologic maps were compiled at 1:500,000 and 1:2 million scales of the Mangala Valles, Kasei Valles, Chasma Boreale (north polar), and Planum Australe (south polar) areas, and a study was begun of the topography and surface roughness characteristics of the Mangala Valles site. Geologic mapping has been greatly facilitated by specially enhanced, high-resolution Viking photographs, which clarify stratigraphic relations of units unrecognized earlier. Photoclinometric profiles of topographic features provide width and depth measurements of four classes of channels, the thickness of some volcanic units, and the throw on some faults. Estimates of the surface roughness of units are calculated using a newly developed USGS computer program and using measurements derived from Earth-based radar

Asymmetrical Force Production in the Maneuvering Flight of Pigeons

Downstroke force produced by Rock Doves (Columba livia) as they negotiated an obstacle course was measured using in vivo recordings of delto-pectoral crest strain. During this slow $(\u3c6\ {\rm m}\ {\rm s}^{-1})$ , maneuvering flight, pigeons produced a series of four to six successive wingbeats in which the wing on the outside of the turn produced greater peak force than the wing on the inside of the turn, suggesting that the birds maneuvered in a saltatory manner during slow flight. This asymmetrical downstroke force may be used to increase or reestablish bank lost during upstroke, or it may be directed as thrust to compensate for adverse yaw or create excess yaw to alter the bird\u27s direction of flight. Continuous production of asymmetrical downstroke force through a turn differs from the traditional model of maneuvering flight, in which asymmetrical force is used only to initiate a bank, the forces are briefly reversed to arrest the momentum of the roll and then equalized to maintain the established bank, and the redirected lift of the wings then effects a turn. Although this traditional model probably describes most turns initiated during fast and gliding flight in birds, it underestimates the complexity of maneuvering during slow, flapping flight, where sophisticated kinematics and neuromuscular control are needed to change direction effectively