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Depredation by common ravens often exceeds stakeholders’ levels of acceptance. Common sources of excessive raven damage include loss of young livestock and nest depredation of species of concern, such as desert tortoise, greater sage-grouse, and least tern. USDA/APHIS Wildlife Services applies the avicide DRC-1339 (3-chloro-p-toluidine hydrochloride, CPTH) formulated in an intact-boiled egg bait to reduce such damage under the DRC-1339 Concentrate Livestock, Nest & Fodder Depredations label (EPA No. 56228-29). Although considered extremely effective on corvids, DRC-1339 is a slow acting toxicant and ravens may succumb away from the bait site, preventing the use of carcass recovery as a means to estimate take. To estimate take, Wildlife Services employs a model comprised of a bioenergetics module to predict consumption combined with a toxicological module that predicts mortality based on a probit analysis. This model has recently been revised to improve and standardize take estimates for common raven management activities using the egg baits covered by this label. Common ravens exhibit complex behaviors that impact the amount of bait consumed when offered DRC-1339 egg baits. The approaches to capturing this behavior in the model are presented along with take estimates associated with a range of baiting scenarios.

DRC-1339 (CPTH, 3-chloro-p-tolouidine) is an avicide registered to reduce local populations of selected bird species at feedlots, dairies, and staging areas near rice fields, and to prevent livestock depredation. Additionally, two registrations are specifically for controlling gulls and pigeons. U.S. Department of Agriculture Wildlife Services personnel historically have used a variety of methods to estimate take, including counting carcasses and quantifying reduction in bird activity. Because this avicide is slow-acting and birds usually succumb away from the bait site, carcass recovery provides poor estimates of take. Because of natural variability in bird numbers and activity, quantifying reductions in bird activity is also a poor gauge of efficacy. Scientists at the U.S. Department of Agriculture APHIS Wildlife Services National Wildlife Research Center developed and continue to adapt and refine a model using a bioenergetics approach to estimate consumption and the resulting mortality from DRC-1339 bait consumption. The model estimates take for the major baits used under the feedlot and staging area labels for European starlings, blackbirds, brown-headed cowbirds, and common grackles. Consumption of homogeneous baits (rice, cracked corn, fat pellets) has been well characterized, and take (i.e., mortality) is accurately predicted in the model. However, predictions of take when french fries were used as a bait for controlling starlings at feedlots in Washington State were less accurate. Thus, we modified the model to capture the feeding behavior of birds using this highly heterogeneous bait by removing the dependence on bait mass and simplifying the calculation of dose ingested. The modified model calculates dose directly from the amount of DRC-1339 per calorie consumed instead of from the DRC-1339 concentration per bait consumed. In this paper, we compare estimates of take based on french fry bait mass distributions and caloric contents determined for five different french fry bait types.

Raven populations that depredate livestock, damage agricultural crops, and injure endangered and threatened species, can be managed with egg baits containing the avicide DRC-1339 (3-chloro-p-toluidine). Estimating baiting efficacy is difficult, as DRC-1339 is a slow-acting toxicant. Efficacy estimation is further complicated by the feeding behavior of ravens at bait sites. To evaluate the efficacy of an egg baiting operation, we developed a computer simulation to predict bait consumption by ravens, incorporating a DRC-1339 degradation module to predict DRC-1339 bait concentration at the time of consumption and an effects module to predict the mortality associated with the resulting DRC-1339 dose. Details of the simulation will be presented in the context of predicting baiting efficacy using egg baits in different climatic environments. These preliminary results provide the basis for designing field studies that can be used to improve and validate the model.

Establishing the impact of double-crested cormorants on commercial farmed channel catfish production using visual assessments of cormorant GI tract contents is complicated by, first, the difficulty in distinguishing between partially digested fish of different species, and secondly, the possibility that the fish appearing in the diet have a natural source of origin. We analyzed the fatty acid profiles of selected game fish and farm-raised channel catfish to establish profiles that may allow for the application of this technique in establishing cormorant foraging patterns. We obtained for analysis farm-raised channel catfish from three commercial producers and one research facility. For comparison, we also collected channel catfish, gizzard shad, green sunfish, bluegill, and largemouth bass from natural waterways. A total of 12 sample groups were analyzed. Lipids were extracted using a modified Folch extraction and trans-esterified in 3N HCl in methanol. The resultant fatty acids were identified using gas chromatography/mass spectrometry. The relative mass percent distributions for the major fatty acids were calculated for each individual. A classification tree analysis was performed to identify groupings based on these individual fish distributions. These preliminary results have led us to conclude that it is possible to distinguish not only between farm-raised channel catfish and game fish in the diet of cormorants, but that it may be possible to identify the source of the farm-raised channel catfish in the diet. The management implications are that it may be possible, based on fatty acid analysis of GI tract contents of cormorants, to assess the actual impact of birds from a given roost or colony on a specific channel catfish producer.

A probabilistic model was validated for estimating avian mortality associated with the application of the avicide CPTH (3-chloro-4-methylaniline hydrochloride) to minimize sprouting rice damage in the southern United States. CPTH exposures for individual birds were predicted by random sampling from species-specific non-parametric distributions of bait seed consumption and CPTH residues detected on individual bait seeds. Mortality was predicted from the species-specific exposure versus mortality relationship. Individual variations in this response were captured in the model by Monte Carlo sampling from species-specific distributions of slopes and median toxicity values (LD50) for each bird. The model was used to evaluate the effects of formulation, bait preparation and application procedures on target and non-target mortalities. The results of these analyses indicate that: 1) decreasing the concentration of CPTH on the treated bait seeds from 400 to 300 μg CPTH/seed will improve bait performance by decreasing non-target mortalities, 2) the current dilution ratio of 1 treated seed to 25 diluent seeds is optimal and 3) preparing a bait seed product in which CPTH is homogeneously distributed throughout the bait seed mixture will significantly increase bait performance by increasing red-winged blackbird (target) mortality and decreasing mortality for savannah sparrows and meadowlarks (non-targets).

Due to the slow-acting nature of the avicide, DRC-1339 (3-chloro-p-toluidine hydrochloride), birds may travel considerable distances following ingestion of lethal quantities of treated bait. Confirmation of DRC-1339 bait consumption in bird carcasses collected temporally and spatially removed from a baiting site has been problematic, particularly after a prolonged period of time, due to the decomposition of the carcass. To establish a temporal baseline for analytical methods developed for determining DRC-1339 residues in bird tissues, mourning doves were fed 2% DRC-1339-treated rice or control untreated rice. Birds were euthanized after 24 hrs. Bird carcasses were allowed to decompose for 1, 2, 7, 14, or 21 days at ambient temperatures (22.4 ± 0.7°C). GI tract and breast tissue samples were collected and solvent extracted for analysis by GC/MS for DRC-1339 residues. Residues could be detected in the GI tract samples up to 14 days after dosing. Linear regression analysis of the data indicated the possibility of detecting residues in GI tract samples for up to 23 days under similar environmental conditions for carcass decomposition. These results provide a time frame under which it is possible to confirm DRC-1339 bait consumption in birds by analyzing for residues in tissues from carcasses collected after a baiting operation.

In late summer, red-winged blackbirds forage heavily on ripening sunflower crops in the Dakotas. Sunflower achenes have a distinct fatty acid profile that should influence the fatty acid composition in tissues of these birds. To determine if fatty acid composition in tissue could be used as a biomarker indicating dietary history, we fed 18 red-winged blackbirds a sunflower diet for 2 weeks and compared fatty acid profiles in their muscle and liver tissues to a control group of red-winged blackbirds (n = 15) fed a birdseed mix supplemented with safflower seed. Three subjects from each treatment group were sacrificed at Day 0, 7, 14, and 21, with Day 0 the day the treated group was switched to sunflower. The remaining birds were sacrificed on Day 35. Breast muscle and liver tissue were collected, extracted, and analyzed for levels of linoleic, oleic, palmitic, and stearic acids. Differences existed in levels of all 4 fatty acids between treatment groups pooled across time (P ≤ 0.05, ANOVA). When comparing fatty acid profiles between treated and controls by day sacrificed, we observed differences in levels of ≥1 of the fatty acids at Day 7, 14, and 21 in breast muscle, and Day 7 and 14 in liver tissue (P ≤ 0.05, t-test). Within-bird comparisons of fatty acid levels in liver and breast indicated temporal lags in metabolism between tissue types (P ≤ 0.05, paired t-test). Our results demonstrated that fatty acids profiles in body tissues can be used as biomarkers to verify recent foraging in sunflower by red-winged blackbirds.

Caffeine is an effective, economical, and environmentally safe avian repellent and including sodium benzoate in subsequent formulations enhances the solubility of caffeine thus proving to be an applicable, nonlethal alternative for managing blackbird impacts to agricultural production.

Alpha-chloralose (AC) is used to capture nuisance waterfowl so that they can be relocated. Concerns for food safety limit its use prior to or during the waterfowl hunting season. To determine its half-life in tissue, we administered AC to adult male (n = 7) and female (n = 5) mallard ducks (Anas platyrhynchos) via oral gavage. A gel capsule containing 100 μCi of radioactive AC (14C-AC) and sufficient nonlabeled AC to produce a dose of approximately 30 mg/kg was given to each duck. The ducks were euthanized at 2, 6, 10, and 18 hours postdosing (n = 3 per exposure period), and tissue samples were collected for radioactive analysis. Residues observed in edible tissues from ducks dosed with radioactive AC demonstrated a delayed uptake as the duck was under the anesthetic effects of the AC. Following the period when the ducks were unconscious, most of the AC was rapidly excreted from the body with mean half-life (t½) values of 9.0 hours, 9.8 hours, and 9.1 hours for breast muscle, liver, and skin, respectively. An approximation of total excretion (99%) was made by taking 7 times the t½, resulting in values of between 27 to 33 hours post-exposure. These results suggest that tissues from mallard ducks are safe for human consumption 48 hours after dosing, a period that is significantly shorter than the FDA-required 30-day withdrawal period. [ABSTRACT FROM AUTHOR]

Bovine tuberculosis, caused by Mycobacterium bovis, is a zoonotic disease of international public health importance. Ante-mortem surveillance is essential for control; however, current surveillance tests are hampered by limitations affecting ease of use or quality of results. There is an emerging interest in human and veterinary medicine in diagnosing disease via identification of volatile organic compounds produced by pathogens and host-pathogen interactions. The objective of this pilot study was to explore application of existing human breath collection and analysis methodologies to cattle as a means to identify M. bovis infection through detection of unique volatile organic compounds or changes in the volatile organic compound profiles present in breath. Breath samples from 23 male Holstein calves (7 non-infected and 16 M. bovis-infected) were collected onto commercially available sorbent cartridges using a mask system at 90 days post-inoculation with M. bovis. Samples were analyzed using gas chromatography-mass spectrometry, and chromatographic data were analyzed using standard analytical chemical and metabolomic analyses, principle components analysis, and a linear discriminant algorithm. The findings provide proof of concept that breath-derived volatile organic compound analysis can be used to differentiate between healthy and M. bovis-infected cattle. [ABSTRACT FROM AUTHOR]

Bovine tuberculosis, caused by Mycobacterium bovis, is a zoonotic disease of international public health importance. Ante-mortem surveillance is essential for control; however, current surveillance tests are hampered by limitations affecting ease of use or quality of results. There is an emerging interest in human and veterinary medicine in diagnosing disease via identification of volatile organic compounds produced by pathogens and host-pathogen interactions. The objective of this pilot study was to explore application of existing human breath collection and analysis methodologies to cattle as a means to identify M. bovis infection through detection of unique volatile organic compounds or changes in the volatile organic compound profiles present in breath. Breath samples from 23 male Holstein calves (7 non-infected and 16 M. bovis-infected) were collected onto commercially available sorbent cartridges using a mask system at 90 days post-inoculation with M. bovis. Samples were analyzed using gas chromatography-mass spectrometry, and chromatographic data were analyzed using standard analytical chemical and metabolomic analyses, principle components analysis, and a linear discriminant algorithm. The findings provide proof of concept that breath-derived volatile organic compound analysis can be used to differentiate between healthy and M. bovis-infected cattle. [ABSTRACT FROM AUTHOR]

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) C18 column and a UV variable wavelength detector (λ=347 nm) with a mobile phase of 60:40 (v/v) ACN–H2O, 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. [Copyright &y& Elsevier]