Foraging Behavior of Swainson\u27s Thrushes (Catharus ustulatus) During Spring Migration through Arkansas

Foraging behavior of Swainson’s Thrushes on spring migration was studied in western Arkansas in the spring of 2013 and 2014. Observations were made in two forested field sites, one of them urban and the other suburban. The former had a significantly higher woody stem area (cm2) than the latter. For each foraging observation, the following three parameters were noted: Foraging Stratum (Ground, Shrub, Sapling, Sub canopy, and Canopy); Foraging Substrate (Ground/Litter, Herb, Foliage, Bark, and Air); and Foraging Maneuver (Glean, Probe, Dive/Glean, Hover, Jump Hover, and Hawking). We tested the hypotheses that these foraging variables differed significantly between the urban and suburban sites, and between the two years. These hypotheses were rejected for all three parameters. The consolidated data from both the sites and years revealed that a significantly higher proportion (67%) of the observations were on the Ground stratum, compared to the Shrub (13.7%) and Sapling strata (13%). Similarly, a significantly higher proportion (66%) of the foraging substrate used was Ground/Litter, followed by Foliage (16.7%) and Bark (15.8%). Gleaning was the most common foraging maneuver used (71.5%), and was significantly higher than Probing (12.3%) and Dive Gleaning (8.4%)

Three-fold way to extinction in populations of cyclically competing species

Species extinction occurs regularly and unavoidably in ecological systems. The time scales for extinction can broadly vary and inform on the ecosystem's stability. We study the spatio-temporal extinction dynamics of a paradigmatic population model where three species exhibit cyclic competition. The cyclic dynamics reflects the non-equilibrium nature of the species interactions. While previous work focusses on the coarsening process as a mechanism that drives the system to extinction, we found that unexpectedly the dynamics to extinction is much richer. We observed three different types of dynamics. In addition to coarsening, in the evolutionary relevant limit of large times, oscillating traveling waves and heteroclinic orbits play a dominant role. The weight of the different processes depends on the degree of mixing and the system size. By analytical arguments and extensive numerical simulations we provide the full characteristics of scenarios leading to extinction in one of the most surprising models of ecology

Gating of high-mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures

We investigate high-mobility two-dimensional electron gases in AlGaAs heterostructures by employing Schottky-gate-dependent measurements of the samples' electron density and mobility. Surprisingly, we find that two different sample configurations can be set in situ with mobilities diering by a factor of more than two in a wide range of densities. This observation is discussed in view of charge redistributions between the doping layers and is relevant for the design of future gateable high-mobility electron gases

Status, Dispersal, and Breeding Biology of the Exotic Eurasian Collared-Dove (Streptopelia decaocto) in Arkansas

The exotic Eurasian Collared-Dove (Streptopelia decaocto) was first sighted in Arkansas at Harrison (Boone Co.) on 25 June 1989. Since this initial sighting the species has grown in numbers and is now present in 42 of 75 counties across the state. In the spring and summer of 2009 and 2010, 20 nests were observed in the urban areas of Fort Smith (Sebastian County). Fifteen of the 20 nests (75%) were located on human-made structures of which 13 (65%) were on an electrical substation and two (10%) were on utility poles. The remaining 5 nests (25%) were in trees. Mean nest height was 7.62 m (n = 20 nests), and the mean width of the nest site support was 40 cm (n = 6 nests). Thirteen of the 20 nests (65%) yielded fledgling(s). Three focal nests were chosen for intense observation. Nest building lasted 1 to 3 days (mean = 2 days); incubation period was 15 days; and fledging occurred 17-18 days after hatching (n = 3 nests). A total of 6 young fledged from these 3 nests

Absorbing phase transition in a conserved lattice gas with random neighbor particle hopping

A conserved lattice gas with random neighbor hopping of active particles is introduced which exhibits a continuous phase transition from an active state to an absorbing non-active state. Since the randomness of the particle hopping breaks long range spatial correlations our model mimics the mean-field scaling behavior of the recently introduced new universality class of absorbing phase transitions with a conserved field. The critical exponent of the order parameter is derived within a simple approximation. The results are compared with those of simulations and field theoretical approaches.Comment: 5 pages, 3 figures, accepted for publication in J. Phys.