David L. Otis

Autocorrelation of location estimates and the analysis of radiotracking data

The wildlife literature has been contradictory about the importance of autocorrelation in radiotracking data used for home range estimation and hypothesis tests of habitat selection. By definition, the concept of a home range involves autocorrelated movements, but estimates or hypothesis tests based on sampling designs that predefine a time frame of interest, and that generate representative samples of an animals movement during this time frame, should not be affected by length of the sampling interval and autocorrelation. Intensive sampling of the individuals home range and habitat use during the time frame of the study leads to improved estimates for the individual, but use of location estimates as the sample unit to compare across animals is pseudoreplication. We therefore recommend against use of habitat selection analysis techniques that use locations instead of individuals as the sample unit. We offer a general outline for sampling designs for radiotracking studies.

Effects of Stress on Susceptibility of Naive Channel Catfish in Immersion Challenge with Edwardsiella ictaluri

Abstract The effects of stress on the susceptibility of fingerlings of channel catfish Ictalurus punctatus to Edwardsiella ictaluri during immersion challenges were evaluated. Channel catfish fingerlings were exposed to a standardized confinement stressor for 30 min. Infections were established in stressed and nonstressed channel catfish fingerlings by exposure to E. ictaluri under aerated static conditions for 24 or 48 h. Stress and increased time of static bacterial exposure significantly decreased the survival of channel catfish fingerlings after immersion challenge. This study established a relationship between a behavioral stressor (confinement) and increased susceptibility of channel catfish to E. ictaluri infection. From estimates ofexperimental error, a relationship between the precision of the challenge system and the number of replicate aquaria per treatment was established. This analysis indicated that the immersion challenge is associated with a high degree of variability, which limits the eff...

Evaluation of Methyl Anthranilate and Starch-Plated Dimethyl Anthranilate as Bird Repellent Feed Additives

We conducted 3 experiments to evaluate the effectiveness of methyl anthranilate (MA) as a bird repellent. In Experiment 1, we examined the repellency of several technical MA concentrations in 6-hour tests―a time period similar to the duration of exposure of livestock feed in feedbunks. In Experiment 2, we determined the lowest concentration of technical MA that was as effective as 1.0% dimethyl anthranilate starch (DMA; our field-tested standard). Finally, in Experiment 3, we explored the repellency of starch-encapsulated MA to grouped red-winged blackbirds (Agelaius phoeniceus) and European starlings (Sturnus vulgaris) in an outdoor aviary. Experiments 1 and 2 indicated that 0.4-0.5% MA was as repellent as 1.0% DMA-starch. Experiment 3 showed that although 1.0% MA reduced consumption by grouped starlings and red-wings in 2-choice tests, only starlings avoided treated food in 1-choice tests. Red-wings habituated to the substance, and consumption returned to baseline levels by treatment Day 3. We conclude that MA is an economical alternative to DMA, although species and/or social factors may influence repellency

Analysis of habitat selection studies with multiple patches within cover types

Current statistical methods are inadequate for evaluation of the relation between spatial pattern of the landscape and observed patterns of habitat use by individuals or populations. For example, traditional habitat selection analysis methods do not use information about the size and distribution of the several patches of each cover type that may exist within the study area. Statistical tests are presented for hypotheses about disproportional use of cover types and patches within cover types. These tests require that use of individual patches is recorded, as well as the size of individual patches. Different designs are considered in which there are (1) single or multiple samples of use, and (2) equal or unequal habitat availability. Formulas for calculating Type II statistical errors of the tests are presented and Monte Carlo simulation is used to assess the accuracy of the formulas and to check the Type I error rates of the proposed test statistics. With adequate sample sizes, Type II error formulas can be a useful tool for planning of habitat selection studies. An example analysis is presented of a hypothetical study of habitat selection by ring-necked pheasants (Phasianus colchicus) in a Midwestern landscape. The proposed tests also represent a contribution toward bringing together concepts of landscape ecology and wildlife habitat selection.

Avian Communities and Habitat Relationships in South Carolina Piedmont Beaver Ponds

Abstract Beaver ponds are a widely distributed and abundant wetland resource in the southeastern United States, but their value as avian habitat is poorly documented. We sampled bird populations at six South Carolina Piedmont beaver ponds from April 1993 through June 1994 to examine seasonal community composition and discern microhabitat variables that are associated with bird group abundance and richness. The resident/short-distance migrant group and the neotropical migrant group were most abundant in the spring seasons and waterbirds were least abundant. In fall and winter the resident/short-distance migrant group was most abundant at all ponds with the exception of one pond in winter, which had very high use by waterfowl. Seasons were generally most important in predicting bird species richness and abundance of the resident/short-distance migrant group. Vegetation interspersion, patch evenness, plant richness and total area were most important in explaining abundance of waterfowl, waterbirds, neotropical migrants and woodpeckers, respectively.

Dimethyl and methyl anthranilate and methiocarb deter feeding in captive Canada geese and mallards

We evaluated the repellency of dimethyl anthranilate (DMA) and methyl anthranilate (MA) in 1- and 2-choice feeding trials with and without methiocarb (MB) on captive Canada geese (Branta canadensis) and mallards (Anas platyrhynchos) because both species cause crop damage or nuisance problems. In 2-choice trials, concentrations of 1% (g/g) DMA and MA were avoided by both species. Concentrations of 2% DMA and MA, and an economically similar concentration of MB (0.1%), reduced (P≤0.005 and P≤0.01, respectively) consumption by geese and ducks in 1-choice tests. Of the 3 materials, MA and MB were the strongest feeding deterrents and warrant further testing in the field

Analysis of the Influence of Spatial Pattern in Habitat Selection Studies

Design and analysis of wildlife habitat selection studies typically do not assess the effect of spatial pattern on the habitat selection process. Effects of landscape scale pattern on habitat selection cannot be accomplished without replicate study areas, because pattern is a single, albeit multifaceted, attribute of an area. For a single area, however, the influence of pattern-related characteristics, such as shape and edge shared with adjacent patches, can be estimated by using GLIM (McCullough and Nelder 1983) procedures to model patch-specific frequency counts of animal use as a function of these parameters. This approach is evaluated and illustrated with simulated breeding-bird counts in a South Carolina study area for which a GIS land cover classification is available. A related technique for evaluating whether movement from patch to patch is selective is developed and illustrated for designs that involve collection of trajectory data from monitored individuals. These designs and analyses are feasible given current GIS and GPS technology. Statistical inferences from habitat selection studies should be interpreted within the context of a range of scales at which animals differentiate between patch attributes.

Use of a Computer Simulation Model to Determine the Behavior of a New Survey Estimator of Recreational Angling

Abstract We have recently developed a new estimator of recreational fishing effort. Here we used a simulation model to determine and demonstrate the statistical behavior of this new estimator. The estimator is used with access-intercept surveys and was designed to give accurate, efficient estimates of fishing effort over a geographically large and diverse fishery. Because this is a new estimator, little is known about its behavior. Specifically, the form of the estimators sampling distribution, the variance components (within-day versus between-day), and its t-distribution were unknown and could not be determined analytically. Hence, to assist people who will want to know the statistical properties of this estimator and to characterize it more completely, we studied its behavior numerically by use of a simulation model based on real-world data. Analysis of the simulation results showed the sampling distribution of the estimator to be non-normal when limited to a single survey route; it was more closely a...

Re-analysis of a banding study to test the effects of an experimental increase in bag limits of mourning doves

In 1966-1971, eastern US states with hunting seasons on mourning doves ( Zenaida macroura ) participated in a study designed to estimate the effects of bag limit increases on population survival rates. More than 400 000 adult and juvenile birds were banded and released during this period, and subsequent harvest and return of bands, together with total harvest estimates from mail and telephone surveys of hunters, provided the database for analysis. The original analysis used an ANOVA framework, and resulted in inferences of no effect of bag limit increase on population parameters (Hayne 1975). We used a logistic regression analysis to infer that the bag limit increase did not cause a biologically significant increase in harvest rate and thus the experiment could not provide any insight into the relationship between harvest and annual survival rates. Harvest rate estimates of breeding populations from geographical subregions were used as covariates in a Program MARK analysis and revealed an association between annual survival and harvest rates, although this relationship is potentially confounded by a latitudinal gradient in survival rates of dove populations. We discuss methodological problems encountered in the analysis of these data, and provide recommendations for future studies of the relationship between harvest and annual survival rates of mourning dove populations.

Survival models for harvest management of mourning dove populations

Quantitative models of the relationship between annual survival and harvest rate of migratory game-bird populations are essential to science-based harvest management strategies. I used the best available band-recovery and harvest data for mourning doves (Zenaida macroura) to build a set of models based on different assumptions about compensatory harvest mortality. Although these models suffer from lack of contemporary data, they can be used in development of an initial set of population models that synthesize existing demographic data on a management-unit scale, and serve as a tool for prioritization of population demographic information needs. Credible harvest management plans for mourning dove populations will require a long-term commitment to population monitoring and iterative population analysis.