Bruce C. Thompson

Colonial Waterbird Management in North America

Colonial waterbirds are an important natural resource highly valued by many people in Canada and the United States. The habit of nesting often in large groups makes these birds especially susceptible to problems, such as human disturbance, predation, severe weather events, and competition for nesting habitat. They, like all birds, also face threats from habitat degradation, loss and contamination of their environments, and changes in food webs. Management strategies to deal with these problems include habitat preservation and restoration, the elimi- nation of toxic chemicals from the environment, reduction of predation, competition, and disturbance at nesting sites, reintroduction of species to nesting sites from which they have been eliminated, and fisheries management from a multispecies ecosystem perspective. Techniques are discussed and examples provided. A few colonial waterbird species have increased greatly in numbers and now pose problems for other bird species or are in conflict with people. Management is also involved in the control of such problem birds. Strategies include habitat modifications and scaring or killing problem birds. There is a continuing need for information and research to allow appropriate management to be applied. Regular surveys and inventories are necessary on a regional basis to detect trends in population status and to minimize and mitigate conflicts with human activities. Studies of population demography are needed for species declining in numbers, and research into species ecology is often necessary before appropriate manage- ment can be applied. Additional techniques to reduce conflicts between birds and humans are also needed. Human activities are likely a major limiting factor for some species, and, conversely, humans are largely responsible for the increases of several species that have become problems. Continued education of the public and of conservation management agencies to the role and importance of colonial waterbirds is important. Many species are likely to continue to suffer from gradual incremental loss and degradation of habitats, and a conservation strategy for the protection of these birds throughout North America is recommended.

Reliability of the cementum annuli technique for estimating age of black bears in New Mexico

Abstract Black bear (Ursus americanus) populations are most often managed based on sex and age composition of hunter-killed bears, but few studies have evaluated the method used to determine age. We assessed the accuracy and consistency of aging black bears in New Mexico using the cementum annuli technique by examining age estimates obtained for research-captured and hunter-killed bears. Age estimates were 80% accurate for 30 teeth obtained from 26 known-age bears. Age estimates were consistent with field estimates of age-class for 76% of 232 teeth obtained from captured bears when actual age was not known. Age estimates were consistent between paired teeth for 74% of 232 pairs taken from hunter-killed bears on the same day but for only 46% of 61 pairs taken from study bears during the same or different years. Errors or inconsistencies in age estimation increased with known or estimated age, certainty codes provided by the laboratory, and tooth breakage, but these 3 factors were correlated. Accuracy and consistency also were lower when teeth were removed during the den season. Evidence did not indicate any difference in accuracy and consistency between sexes. In comparisons of 2 blind samples obtained independently, estimated age composition of the harvest did not differ (P=0.92). Accuracy and consistency of the cementum annuli aging technique were relatively high for bears with known or estimated ages <5 years old; therefore, the method appeared adequate for assessing age composition of annual hunter harvests in New Mexico.

Mark-resight superpopulation estimation of a wintering elk Cervus elaphus canadensis herd

Abstract We executed four mark-resight helicopter surveys during the winter months January–February for each of the three years 1999–2001 at 7–10 day intervals to estimate population size of a wintering elk Cervus elaphus canadensis herd in northern New Mexico. We counted numbers of radio-collared and uncollared elk on a simple random sample of quadrats from the study area. Because we were unable to survey the entire study area, we adopted a superpopulation approach to estimating population size, in which the total number of collared animals within and proximate to the entire study area was determined from an independent fixed-wing aircraft. The total number of collared animals available on the quadrats surveyed was also determined and facilitated detectability estimation. We executed superpopulation estimation via the joint hypergeometric estimator using the ratio of marked elk counted to the known number extant as an estimate of effective detectability. Superpopulation size estimates were approximately four times larger than previously suspected in the vicinity of the study area. Despite consistent survey methodology, actual detection rates varied within winter periods, indicating that multiple resight flights are important for improved estimator performance. Variable detectability also suggests that reliance on mere counts of observed individuals in our area may not accurately reflect abundance.

Denning chronology and design of effective bear management units

Abstract Reports on the effectiveness of using late fall hunting seasons to reduce the proportion of female black bears (Ursus americanus) in the harvest are limited, and the geographic scale over which the technique functions as intended has not been examined. During 1992–2000, we radio-equipped black bears in New Mexico, USA, obtained estimates of 175 den entry and 137 den emergence dates, and used New Mexico Department of Game and Fish harvest data (1985–2000) to test for differences in proportion of females in the harvest relative to denning chronology. Bears in northern New Mexico entered dens earlier and emerged later than bears in southern New Mexico (P ≤ 0.001). In northern New Mexico bears displayed the typical pattern of earlier entry and later emergence by reproductive females, proportion of females in the harvest varied over time as expected, and late fall seasons were effective (P ≤ 0.10). In contrast, denning chronology did not differ by sex in southern New Mexico, proportion of females in the harvest did not change over time, and late fall seasons were not effective (P ≥ 0.18). Manipulation of hunting season dates to influence female mortality can be an effective tool, however our study provides an example of an area where denning chronology did not differ by sex and late seasons were not effective. We also observed regional differences in timing of entrance and emergence, which suggest that scale of application may be key. In management jurisdictions that encompass ecologically distinct areas, cover a wide range of latitudes, or are mountainous, successful use of the technique may depend on knowledge of denning chronology at multiple locations and appropriate designation of hunting unit boundaries, season dates, and data analysis units.

Elk Distributions Relative to Spring Normalized Difference Vegetation Index Values

Rocky Mountain elk (Cervus elaphus) that winter near San Antonio Mountain in northern New Mexico provide important recreational and economic benefits while creating management challenges related to temporospatial variation in their spring movements. Our objective was to examine spring distributions of elk in relation to vegetative emergence as it progresses across the landscape as measured by remote sensing. Spring distributions of elk were closely associated with greater photosynthetic activity of spring vegetation in 2 of 3 years as determined using NDVI values derived from AVHRR datasets. Observed elk locations were up to 271% greater than expected in the category representing the most photosynthetic activity. This association was not observed when analyses at a finer geographic scale were conducted. Managers facing challenges involving human-wildlife interactions and land-use issues should consider environmental conditions that may influence variation in elk association with greener portions of the landscape.

Evaluating Consistency of Categorizing Biodiversity Management Status Relative to Land Stewardship in the Gap Analysis Program

The gap analysis process provides an overview of the distribution and conservation status of several components of biodiversity. Lands are categorized relative to management status, the degree to which an area is managed to maintain biodiversity. This study examines how various socio-politicalgroups interpret and apply the management status codes used to categorize land tracts in gap analysis. A key finding is the considerable variation among individuals in their application of the status codes. This shows a large degree of uncertainty about the land tracts and the status codes, and suggests the need to develop an objective and repeatable management categorization process.

HABITAT CHARACTERISTICS OF ASHMUNELLA (GASTROPODA: PULMONATA: POLYGYRIDAE) AT WHITE SANDS MISSILE RANGE AND FORT BLISS, NEW MEXICO

Abstract We studied the habitat characteristics of 7 species of montane land snails in the genus Ashmunella in southern New Mexico from July 1999 to September 2000. We compared 9 numeric variables and 4 categorical variables by species. Geographic differences in microhabitat variables exist among these species; however, these differences tend to be obscured when comparing species, because some species are ecological generalists that occupy a wide range of habitat types. Although this study determined that different populations occupy ecologically distinct habitats in a broad range of environmental conditions, it remains unclear whether these factors influence the morphological characters on which past workers assigned species status. Management plans for the conservation of these species should take careful note of demonstrated habitat differences among and within the species.