Search

We tested a bioenergetics model integrated within a mortality model that estimates numbers of European starlings (Sturnus vulgaris) poisoned with the avicide, Compound DRC-1339 Concentrate. The bioenergetics model predicted daily metabolic rate. Accuracy and reliability of this variable is critical because other algorithms (e.g., toxicity regressions, feeding behavior) in the mortality model depend on metabolic rate to calculate the amount of DRC-1339 ingested per bird. We tested the bioenergetics model by comparing its estimates of metabolic rate with those generated from measuring feeding rates of caged starlings during a feeding trial conducted outdoors during January 2008. Over the 12-day feeding trial, daily feeding rates of caged starlings indicated that metabolic rates ranged from 157?kJ/bird per day to 305?kJ/bird per day. The bioenergetics model predicted metabolic rates ranging from 208?kJ/bird per day to 274?kJ/bird per day. There was no difference between these 2 independently derived estimates of daily metabolic rate (paired t-test: t(11)?=?1.4, P?=?0.18). Using 95% confidence intervals calculated from variation of feeding rates among cages (n?=?4, 6?birds/cage), the bioenergetics model's estimates were within 95% confidence intervals on 9 of 12 days and greater than the upper 95% confidence interval on 3 days. Daily estimates of metabolic rate were directly correlated between the bioenergetics model and the feeding-rate model (r12?=?0.57, P?=?0.05). A broad range of temperatures (-17°C to 14°C), wind speeds (0–40?km/hr), and percent cloud cover (0–100%) were encountered during the feeding trial. The bioenergetics model's predictions appeared robust to varying meteorological conditions typical of winters in middle latitudes of the interior United States. Compound DRC-1339 Concentrate is used by USDA Wildlife Services to manage chronic infestations of starlings at livestock facilities, which occur mainly during fall and winter. Compared to other methods used for estimating DRC-1339 mortality (e.g., counting birds pre- and posttreatment), bioenergetics modeling should improve the mortality model's overall accuracy and precision. © The Wildlife Society, 2011

Abstract:Nonlethal management alternatives are needed to reduce avian depredation of agricultural crops. Caffeine has promise as an effective, economical, and environmentally safe avian repellent, yet formulation improvements are needed for field applications. We included sodium benzoate in subsequent formulations to enhance the solubility of caffeine. Red-winged blackbirds (Agelaius phoeniceus) discriminated between untreated rice and rice treated with 250 ppm or 10,000 ppm caffeine and sodium benzoate in captivity. We observed a positive concentration-response relationship among birds offered rice treated with 250 ppm, 1,000 ppm, 2,500 ppm, 5,000 ppm, 10,000 ppm, or 20,000 ppm caffeine and sodium benzoate. Relative to the pretreatment of the concentration-response test, repellency was >85% for rice treated with our 2,500- to 20,000-ppm treatments. We conducted seed germination experiments and associated residue analyses to evaluate the potential phytotoxicity of various caffeine formulations under controlled environmental conditions. The optimized formulation enhanced the solubility of tank mixtures and ameliorated the negative impacts of seed treatments to germination. Our caffeine formulation provides an applicable, nonlethal alternative for managing blackbird impacts to agricultural production.

A method for the high-performance liquid chromatography (HPLC) determination of nicarbazin uptake and excretion in ducks is presented. The method uses few clean-up steps and provides a rapid assessment of nicarbazin excretion by measuring the analyte 4,4′-dinitrocarbanalide (DNC). During method development the effect of extraction volume, number of extractions, mobile phase composition, column temperature, and injection volume were varied to optimize sensitivity and achieve as short a run time as possible. For our purposes, a 2×5.0 ml 1:1 dimethyl formamide (DMF):acetonitrile (ACN) extraction injected (40 ml) into an HPLC system equipped with a Keystone octadecylsilyl (ODS) C 18 column and a UV variable wavelength detector ( λ =347 nm) with a mobile phase of 60:40 (v/v) ACN-H 2 O, at a flow-rate of 1.0 ml/min at a column temperature of 35 °C provided adequate resolution and an acceptable total run time. Studies conducted during method development for inter-day recovery efficiencies for 0.46, 1.8 and 88.5 μg/g fortified samples ( n =3) had mean recoveries of 91, 94 and 97% and intra-day ( n =3) recoveries at the same fortification levels of 103, 94, and 92%. The method has been used successfully in excretion studies of nicarbazin in ducks.

Manganese oxides in soils may be sites for sorption of heavy‐metal cations, but the roles of pH‐dependent charge and oxide mineralogy remain unclear as controls on exchangeability of the metals. A model soil‐oxide system tested the effect of pH on the amount and form of Zn retained in exchangeable or nonexchangeable fractions on birnessite‐hausmannite‐coated sand or pyrolusite‐coated sand. Two Zn treatments, 250 and 2500 µmol/kg sand, were used to determine the effect of Zn concentration on the form of Zn retained. Surface charge for the birnessite‐hausmannite‐coated sand and pyrolusite‐coated sand increased across the pH range from 4 to 7.6, but surface charge was found to be a poor predictor of the amount and form of Zn retained even though the oxides increased Zn sorption by the sand. The distribution between the exchangeable and nonexchangeable Zn fractions changed from predominantly exchangeable to predominantly nonexchangeable Zn due to the oxide coatings and higher pHs. The difference in the exchangeable and nonexchangeable Zn retention by the two sands was attributed to mineralogical constraints on the type of surface functional groups. The mechanisms proposed to account for the nonexchangeable retention of Zn on both oxide‐coated sand surfaces were hydrolysis of the Zn followed by chemisorption to the oxide surface.

Mineralogy of Fe‐oxide coatings in soils may influence pH‐dependent sorption of heavy metals, but exchangeability of retained metals needs to be better understood to improve predictions of bioavailability. A laboratory study tested the effect of pH on the amount and form of Zn retained in exchangeable (extractable with 1 MKNO3) or nonexchangeable forms on goethite‐ and hematite‐coated sand. Batch equilibrations with 250 and 2500 µmol Zn(NO3)2/kg coated or uncoated sand were used to determine concentration effects on the form of Zn retained. Cation‐exchange capacity (CEC) of the goethite‐ or hematite‐coated sand increased with pH (4–7.6), but surface charge was a poor indicator of the amount and form of Zn retained. The goethite‐coated sand retained the Zn principally in a nonexchangeable form, while the hematite‐coated sand retained the Zn in both exchangeable and nonexchangeable forms. The distribution between the exchangeable and nonexchangeable Zn fractions changed from predominantly exchangeable to predominantly nonexchangeable Zn retention as pH increased in both oxide systems. The dominance of nonexchangeable‐Zn sorption by goethite was attributed to surface‐induced hydrolysis by OH groups, while O atoms of hydrated hematite and uncoated sand surfaces were hypothesized to be sorbing Zn in exchangeable forms.

Better information is needed to predict how soil acidity affects exchangeability of heavy metals in soils dominated by Fe and Mn oxides with pH‐dependent charge. Our laboratory study sought to separate exchangeable and nonexchangeable Zn sorbed by four B horizon soil materials with varied mineralogy and sesquioxide contents. A Myersville silt loam (fine‐loamy, mixed, mesic Ultic Hapludalf), a Jackland sandy loam (fine, mixed, mesic Aquic Hapludalf), a Christiana sandy loam (clayey, kaolinitic, mesic Typic Paleudult), and an Evesboro loamy sand (mesic, coated Typic Quartzipsamment) were compared for the exchangeability of Zn as a function of pH. Surface charge was measured across the pH range of 3.5 to 7.6, a 175 µmol ZnCl2/kg soil treatment was applied, and sorbed Zn was exchanged with K. Cation‐exchange capacity (CEC) was positively correlated with nonexchangeable but not with exchangeable Zn forms. All four soils retained nearly the same amount of Zn, even though CEC ranged from <10 to >80 mmolc/kg. An abrupt transition from exchangeable to nonexchangeable Zn occurred in the pH range 5.6 to 5.9 of the Myersville, Evesboro, and Christiana soils. Differences in oxide mineralogy and proton buffering intensity appeared more important than CEC as controls on the exchangeability of Zn in these soils. This result is germane to predicting retention of heavy metals in sewage‐sludge‐amended agricultural soils.

The daily carbon balance of a plant is determined by the gross input of C, the efficiency of new biomass, and the maintenance requirement of existing biomass. According to models of C utilization in plants, the synthesis efficiency (or yield of growth, Y8) should depend on the nature of the product being synthesized, while the maintenance requirement per unit biomass (m) should depend mainly on the concentration and turnoverate of the protein in existing biomass. Values of Y8and m were determined throughout the ontogeny of grain sorghum [Sorghum bicolor(L.) Moench]. Individual plants were grown and tested under controlled environment conditions (30°C, high light). Carbon balance determinations were made from 28 to 100 d after emergence. The value of Y8was found to increase from 0.70 g C.g C−1to 0.78 g C.g C−1, while mdecreased from 24 mg C.g C−1.d−1for young plants to 6 mg C.g C−1. d−1for mature plants. It is suggested that the changes in Yg reflect changes in the composition of the end products of biosynthesis. Protein concentration was found to decrease with age. The efficiency of synthesis of proteins is less than that of the carbohydrates that make up the bulk of plant tissue. A decrease in protein synthesis could therefore explain the increase in Y8. The decrease in mafter anthesis was much greater than the decrease in protein concentration. It therefore seems likely that a large fraction of the protein in the plants during grain filling was structural or storage protein that was not being rapidly turned over.

Methods are developed to extract and quantitate the avicide 3-chloro-p-toluidine hydrochloride (CPT HCl) from rough-hulled rice and ethyl-cellulose-coated rice baits using high-performance liquid chromatography. The mobile phase used in the ethyl-cellulose-coated rice matrix method is an acetonitrile(ACN)—phosphate buffer (60:40) at pH 8, and the rough-hulled rice matrix method uses an ACN—phosphate (70:30) buffer at pH 2. Increased retention time is observed for CPT HCl at the higher pH. The two methods have been useful in characterizing different bait formulations in an ongoing pesticide formulation improvement program.