Grazing Impact on Brood Parasitism in the Black-Capped Vireo

Grazing facilitates foraging opportunities for brown-headed cowbirds (Molothrus ater), an obligate brood parasite. Cowbirds can reduce productivity of their hosts, causing some host species to decline in abundance. Thus grazing indirectly influences productivity of some songbirds. The black-capped vireo (Vireo atricapilla) is an endangered songbird with most of its breeding range occurring in areas of ungulate grazing. A contributing factor to its endangered status is brown-headed cowbird parasitism. We monitored 382 black-capped vireo nests from 2012-2013 in Real, Kerr, Bandera, and Edwards Counties, Texas. We investigated how enclosed ungulate (characterized by the presence of enclosed ungulates) and wild ungulate-only (characterized by the absence of enclosed ungulates) systems influenced brood parasitism. We also examined how distance to water (distance from nest to nearest ungulate water source), nest concealment, and grassland in the landscape (proportion of grassland within 3 km of a nest) related to parasitism. Overall parasitism frequency was 30% (n = 166) in 2012 and 31% (n = 216) in 2013, moderate compared with other research, but above a proposed 30% threshold of concern. Grassland in the landscape was not important in predicting brood parasitism in wild ungulate-only grazing systems, but it was important in predicting brood parasitism in enclosed ungulate systems. In enclosed ungulate systems, there was low probability of brood parasitism with a small amount of grassland in the landscape and high probability of parasitism with a large amount of grassland in the landscape. Nest concealment and distance to water were not good predictors of brood parasitism. © 2016 Society for Range Management Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Antispasmodic and bronchodilator activities of St John\u27s wort are putatively mediated through dual inhibition of calcium influx and phosphodiesterase

The crude extract of aerial parts of St John\u27s wort (Hypericum perforatum) (Hp.Cr) and its fractions were studied in vitro for its possible spasmolytic and bronchodilator activities to rationalize some of its medicinal uses. In rabbit jejunum preparations, Hp.Cr caused a concentration-dependent relaxation of both spontaneous and K+ (80 mm)-induced contractions at a similar concentration range (0.1-1.0 mg/mL), similar to that produced by papaverine, whereas verapamil was relatively potent against K+-induced contractions. Hp.Cr shifted the Ca2+ concentration-response curves (CRCs) to the right, similar to that caused by papaverine or verapamil and also caused leftward shift of isoprenaline-induced inhibitory CRCs, similar to papaverine. In guinea-pig tracheal preparations, Hp.Cr caused relaxation of carbachol and K+-induced contractions at similar concentrations (0.01-0.3 mg/mL) and also shifted the isoprenaline-induced inhibitory CRCs to the left, similar to that caused by papaverine. In rabbit aorta preparations at rest, Hp.Cr produced a moderate vasoconstriction, while exhibited vasodilator effect against phenylephrine and K+-induced contractions. Papaverine and verapamil also produced similar non-specific vasodilation, but were devoid of any vasoconstrictor effect. Hp.Cr caused suppression of atrial force of contractions at concentrations about 20 times higher than those that produced inhibitory effect in smooth muscle preparations, similar to papaverine. These results suggest that the spasmolytic effects of Hp.Cr are mediated through dual inhibition of calcium influx and phosphodiesterase (PDE)-like mechanisms, which might explain the medicinal use of St John\u27s wort in the disorders of gastrointestinal and respiratory tracts. Furthermore, the presence of Ca2+ antagonist and PDE inhibitory-like constituents might also be contributing to some extent in the well established use of plant in depression

The terahertz intensity mapper (TIM): Far-infrared balloon mission for spectroscopic galaxy evolution studies

Understanding the formation and evolution of galaxies over cosmic time is one of the foremost goals of astrophysics and cosmology today. The cosmic star formation rate has undergone a dramatic evolution over the course of the last 14 billion years, and dust obscured star forming galaxies (DSFGs) are a crucial component of this evolution. A variety of important, bright, and unextincted diagnostic lines are present in the far-infrared (FIR) which can provide crucial insight into the physical conditions of galaxy evolution, including the instantaneous star formation rate, the effect of AGN feedback on star formation, the mass function of the stars, metallicities, and the spectrum of their ionizing radiatio