Evaluation of Two Methods to Estimate and Monitor Bird Populations

Background: Effective management depends upon accurately estimating trends in abundance of bird populations over time, and in some cases estimating abundance. Two population estimation methods, double observer (DO) and double sampling (DS), have been advocated for avian population studies and the relative merits and short-comings of these methods remain an area of debate. Methodology/Principal Findings: We used simulations to evaluate the performances of these two population estimation methods under a range of realistic scenarios. For three hypothetical populations with different levels of clustering, we generated DO and DS population size estimates for a range of detection probabilities and survey proportions. Population estimates for both methods were centered on the true population size for all levels of population clustering and survey proportions when detection probabilities were greater than 20%. The DO method underestimated the population at detection probabilities less than 30 % whereas the DS method remained essentially unbiased. The coverage probability of 95 % confidence intervals for population estimates was slightly less than the nominal level for the DS method but was substantially below the nominal level for the DO method at high detection probabilities. Differences in observer detection probabilities did not affect the accuracy and precision of population estimates of the DO method. Population estimates for the DS method remained unbiased as the proportion of units intensively surveyed changed, but the variance of th

Changes in Avian and Plant Communities of Aspen Woodlands over 12 Years after Livestock Removal in the Northwestern Great Basin

Riparian and quaking aspen (Populus tremuloides) woodlands are centers of avian abundance and diversity in the western United States, but they have been affected adversely by land use practices, particularly livestock grazing. In 1990, cattle were removed from a 112,500-ha national wildlife refuge in southeastern Oregon. Thereafter, we monitored changes in vegetation and bird abundance in years 1–3 (phase 1) and 10–12 (phase 2) in 17 riparian and 9 snow-pocket aspen plots. On each 1.5-ha plot, we sampled vegetation in 6 transects. Three times during each breeding season, observers recorded all birds 50 m to each side of the plot\u27s 150-m centerline for 25 minutes. We analyzed data with multivariate analysis of variance and paired t tests with p values adjusted for multiple comparisons. In both periods, riparian and snow-pocket aspen produced extensive regeneration of new shoots ( stems/ha and 7079 stems/ha, respectively). By phase 2, a 64% increase in medium-diameter trees in riparian stands indicated successful recruitment into the overstory, but this pattern was not seen in snow-pocket stands, where the density of trees was over 2 times greater. By phase 2 in riparian and snow-pocket stands, native forb cover had increased by 68% and 57%, respectively, mesic shrub cover had increased by 29% and 58%, and sagebrush cover had decreased by 24% and 31%. Total avian abundance increased by 33% and 39% in riparian and snow-pocket aspen, respectively, ground or understory nesters increased by 133% and 67% and overstory nesters increased by 34% and 33%. Similarly, ground or understory foragers increased by 25% and 32%, aerial foragers by 55% and 57%, and overstory foragers by 66% and 43%. We interpreted the substantial regeneration of aspen shoots, increased densities of riparian forbs and shrubs, and increased avian abundances as a multitrophic-level response to the total removal of livestock and as substantial movement toward recovery of biological integrity

Phase I trial of retinol in cancer patients.

Vitamin A (all-trans-retinol) and its analogues are undergoing evaluation as antineoplastic and chemoprevention agents. Because its toxicity and activity are poorly defined, we have completed a phase I trial of retinol. Retinol was administered to 13 cancer patients in daily doses ranging from 100,000 units/m2 to 350,000 units/m2. Neuropsychiatric changes were the earliest dose-limiting symptomatic toxicities, noted in 3 of 5 patients receiving more than 240,000 U/m2 for 3-4 months. Two patients receiving more than 270,000 U/m2 developed hepatomegaly after 3 and 4 months. Liver biopsies were consistent with vitamin A toxicity. Three patients receiving 200,000 U/m2 developed an increase in serum triglycerides concentration. Mild skin and mucous membrane dryness occurred in most patients receiving more than 150,000 U/m2. A mixed response was seen in one patient with melanoma. Because of neuropsychiatric and hepatic toxicity a retinol dose of 200,000 U/m2/day is recommended for future phase II trials

Phase I trial of retinol in cancer patients.

Vitamin A (all-trans-retinol) and its analogues are undergoing evaluation as antineoplastic and chemoprevention agents. Because its toxicity and activity are poorly defined, we have completed a phase I trial of retinol. Retinol was administered to 13 cancer patients in daily doses ranging from 100,000 units/m2 to 350,000 units/m2. Neuropsychiatric changes were the earliest dose-limiting symptomatic toxicities, noted in 3 of 5 patients receiving more than 240,000 U/m2 for 3-4 months. Two patients receiving more than 270,000 U/m2 developed hepatomegaly after 3 and 4 months. Liver biopsies were consistent with vitamin A toxicity. Three patients receiving 200,000 U/m2 developed an increase in serum triglycerides concentration. Mild skin and mucous membrane dryness occurred in most patients receiving more than 150,000 U/m2. A mixed response was seen in one patient with melanoma. Because of neuropsychiatric and hepatic toxicity a retinol dose of 200,000 U/m2/day is recommended for future phase II trials

The Factorial Structure of the Schedule for the Deficit Syndrome in Schizophrenia

Deficit schizophrenia (DS) is considered a distinct subtype within the diagnosis of schizophrenia. While the common assumption is that DS represents a single, cohesive domain of psychopathology, the factorial structure of DS has not been investigated. We assessed 52 individuals with DSM-IV diagnoses of schizophrenia with DS. A principal component analysis (PCA) was conducted on the symptoms of the Schedule for the Deficit Syndrome. The PCA resulted in 2 distinct factors explaining 73.8% of the variance. Factor 1 (avolition) is made up of symptoms of curbing of interests, diminished sense of purpose, and diminished social drive. Factor 2 (emotional expression) is made up of symptoms of restricted affect, diminished emotional range, and poverty of speech. The results indicate that DS is best characterized by these 2 factors. The great majority of participants (86%) displayed DS symptoms from both factors. On average, participants had 4.19 (S.D. = 1.39) symptoms that were primary, enduring, and at least moderate in severity. The mean severity of symptoms was 2.25 (S.D. = 1.06). We discuss possible links between the obtained factors and putative neurobiological mechanisms, as well as directions for future research