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Geology topics

Michael D. Samuel

Publications and source records attributed to Michael D. Samuel.

63 records · Page 4Linked to original sources
USGS1996

Survival of radiomarked canvasback ducklings in northwestern Minnesota

Duckling survival, an important factor affecting annual recruitment, has not been determined adequately for canvasbacks ( Aythya valisineria ). We investigated the magnitude, timing, and causes of mortality of canvasback ducklings from hatch to fledging at the Agassiz National Wildlife Refuge (NWR) in northwestern Minnesota during 1987-90. During the 4 years, 217 day-old ducklings were radiomarked and released in 52 broods. Another 141 ducklings were radiomarked at ≥ to 4 weeks of age. Survival was estimated with the Kaplan-Meier nonparametric estimator and the Weibull parametric model. Most mortalities occurred within 10 days after hatch. Total brood loss occurred in 18 (85%) of 52 broods released. The primary sources of mortality were predation principally by mink ( Mustela vison ), and exposure to precipitation and cold temperature. For combined years, females had lower survival than males ( P =0.03). If the disparate survival between sexes of canvasbacks observed in this study is representative of canvasbacks in their breeding range, this phenomenon contributes to reduced reproductive potential and the male-biased sex ratio of the species.

Minnesota↗
USGS1992

Estimation of wildlife population ratios incorporating survey design and visibility bias

Age and sex ratio statistics are often a key component of the evaluation and management of wildlife populations. These statistics are determined from counts of animals that are commonly plagued by errors associated with either survey design or visibility bias. We present age and sex ratio estimators that incorporate both these sources of error and include the typical situation that animals are sampled in groups. Aerial surveys of elk ( Cervus elaphus ) in northcentral Idaho illustrate that differential visibility of age or sex classes can produce biased ratio estimates. Visibility models may be used to provide corrected estimates of ratios and their variability that incorporates errors due to sampling, visibility bias, and visibility estimation.

Idaho↗
USGS1992

Evaluating habitat selection with radio-telemetry triangulation error

Radio-telemetry triangulation errors result in the mislocation of animals and misclassification of habitat use. We present analytical methods that provide improved estimates of habitat use when misclassification probabilities can be determined. When misclassification probabilities cannot be determined, we use random subsamples from the error distribution of an estimated animal location to improve habitat use estimates. We conducted Monte Carlo simulations to evaluate the effects of this subsampling method, triangulation error, number of animal locations, habitat availability, and habitat complexity on bias and variation in habitat use estimates. Results for the subsampling method are illustrated using habitat selection by redhead ducks ( Aythya americana ). We recommend the subsampling method with a minimum of 50 random points to reduce problems associated with habitat misclassification.

Wisconsin↗
USGS1992

Lead exposure and recovery rates of black ducks banded in Tennessee

American black ducks ( Anas rubripes ) wintering in Tennessee during 1986 to 1988 were tested for exposure to lead. Twelve percent of the birds had blood lead concentrations exceeding 0.2 ppm. Significant differences in the prevalence of lead exposure were found for adults (14.4%) and juveniles (8.2%). Exposed birds had higher blood lead concentrations at one study site, corresponding with a lower survival index.

Tennessee↗
USGS1991

Fall and winter distribution of Canada geese in the Mississippi flyway

Canada geese ( Branta canadensis ) from northern Manitoba and northern Ontario were marked with leg bands and neck bands and observed throughout the Mississippi flyway from 1978 to 1989. We used observations of neck-banded geese within each state to determine the relative fall/winter distribution of the Eastern Prairie Population (EPP) and the Mississippi Valley Population (MVP). Mississippi Valley geese were affiliated with states east of the Mississippi River; EPP geese were affiliated with states west of the Mississippi River. However, we found geographic differences in population distribution within several states. Significant annual changes in distribution also occurred in most states. Management of Mississippi flyway geese should consider the differences in both population dynamics and spatial and temporal distributions of MVP and EPP geese in determining state and flyway harvest objectives.

Journal of Wildlife Management↗
USGS1990

Neck-band retention for Canada geese in the Mississippi flyway

We used capture, harvest, and observation histories of Canada geese ( Branta canadensis ) banded in the Mississippi flyway, 1974-88, to examine the problem of neck-band retention. Methods for the analysis of survival data were used to estimate rates of neck-band retention and to evaluate factors associated with neck-band loss. Sex, age of bird at banding, rivet use, and neck-band type significantly influenced neck-band retention. For most of the resulting cohorts (e.g., sex, age, rivet, and neck-band type categories), neck-band retention rates decreased through time. We caution against using small samples or data collected during short-term studies to determine retention rates. We suggest that observation data be used in neck-band retention studies to increase the efficiency of estimating retention time.

Journal of Wildlife Management↗
USGS1990

Prevalence and characteristics of plastic ingested by Hawaiian seabirds

The prevalence of plastic in 18 species of seabirds at seven study sites in the Hawaiian Islands and Johnston Atoll was studied during 1986 and 1987. Stomach samples were collected by induced emesis from 1,803 live birds of 15 species and during necropsy of 277 dead birds of 5 species. The prevalence of ingested plastic varied greatly among species; age, year of collection, and location of the study site had less pronounced but significant effects. Ingested plastic was absent or uncommon in terns and noddies. Plastic was not found at all in samples from gray-backed terns, Sterna lunata , or white terns, Gygis alba . The prevalence was low in sooty terns, Sterna fuscata (0 to 8%), and brown, Anous stolidus , and black noddies, A. minutus (0 to 3%). Plastic was much more prevalent (67 to 100%) in chicks of black-footed, Diomedea nigripes , and Laysan albatrosses, D. immutabilis . In the 11 other species prevalence ranged from 0 to 44% depending on the age, year of collection, and location. The mean volume of plastic in samples collected at necropsy from Laysan albatross chicks was higher in 1986 (46 cc) than in 1987 (5 cc). Prevalence was generally higher in seabirds which fed at the surface. Fragments of manufactured articles were the most common type of plastic found. Other plastics included pellets, Styrofoam, bottle caps, bags, and sponges. The largest individual item (200 cc) and the greatest diversity of plastic items were found in albatross chicks.

Hawaii↗
USGS1987

Incorporating activity time in harmonic home range analysis

The amount of time an animal spends in particular areas is an important aspect of estimating its home range and activity pattern. Calculations of home range using the harmonic mean can be modified to reflect the amount of time or the type of activity observed at each location. The relative time spent at each location may be used to calculate a time-weighted harmonic home range and associated use pattern. This time-weighted harmonic mean approach provides a method for incorporating bursts of relocation data into a home range analysis or identifying activity areas within the home range.

Journal of Wildlife Management↗