Continued Population Decline Research Articles

Black Brant Harvest, Density Dependence, and Survival: A Record of Population Dynamics

ABSTRACT We analyzed 53 years of banding and band recovery data along with estimates of harvest and population size to assess the role of harvest and density dependence in survival patterns and population dynamics of black brant (Branta bernicla nigricans) over the period 1950–2003. The black brant population has declined steadily since complete annual surveys began in 1960, so the role of harvest in the dynamics of this population is of considerable interest. We used Brownie models implemented in Program MARK to analyze banding data. In some models, we incorporated estimated sport harvest to test hypotheses about the role of harvest in survival. We also examined the hypothesis of density‐dependent regulation of mortality by incorporating estimates of population size as a covariate into models of survival. For a shorter period (1985–2003), we also assessed hypotheses about the role of subsistence harvest and predation as sources of mortality. The best supported model of variation in survival and band recovery allowed survival rates to vary among 2 age classes (juv, second‐yr plus ad brant) and the 2 sexes. We constrained survival probabilities to be constant within decades but allowed them to vary among decades. We also constrained band recovery rates to be constant within decades and to vary in parallel among age and sex classes. We were limited to decade‐specific estimates of survival and band recovery rates because some years before 1984 lacked any banding, and banding in some other years was sparse. A competitive model constrained survival estimates to be the same for males and females. No model containing harvest or population size was competitive with models lacking these covariates (relative quasi‐Akaike's Information Criterion adjusted for small sample size [βQAICc] > 13). In the best supported model, band recovery rates declined from 0.038 ± 0.0028 (F) and 0.040 ± 0.0031 (M) to 0.007 ± 0.0007 (F) and 0.007 ± 0.0007 (M) between the 1950s and 2000s, a clear indication that harvest rates declined over this period. Survival rates increased from 0.70 ± 0.02 and 0.71 ± 0.02 for adult males and females, respectively, in the 1950s to 0.88 ± 0.009 and 0.88 ± 0.01 for males and females, respectively, in the 1990s. Survival rates in the 1990s were among the highest estimated for brant and did not increase in the 2000s with additional reductions in sport harvest. For the shorter data set from 1985 to 2003, models containing covariates for either sport or subsistence harvest were less competitive than models lacking these terms (βQAICc > 3). For the best model containing subsistence harvest, the estimate of β linking subsistence harvest to survival, although imprecisely estimated, was near zero (β = −0.04 ± 0.30), consistent with the hypothesis that subsistence harvest had little impact on survival during this period. We conclude that while harvest likely influenced survival and population dynamics in earlier decades, it is most likely that continued population decline at least since 1990 is a result of low recruitment.

Long-eared Owls, <em>Asio otus</em>: A Review of North American Banding

In Saskatchewan, at the northern edge of the species’ range, the Long-eared Owl (Asio otus) is an irruptive species that has appeared in numbers during major vole (Microtus) outbreaks in 4 of 44 years. Seven other years have had either no bandings or no sightings over large areas. In a search for possible evidence of food-based nomadism, population trends, length and synchronicity of cycles, and longevity, I reviewed all banding in North America through 1998. Prior to banding office computerization (retroactive to 1955), 803 Long-eared Owls had been banded with 33 band encounters (4.1%). Between 1955 and 1998 there were another 10,250 banded by 426 banders with 86 band encounters (0.8%). Encounter records, especially those involving unexpected directions and distances, tend to support but do not prove food-based nomadism. Peaks of migration movements at different long-term stations occurred in different years. There is soft evidence of both 10- and 3-yr cycles. There is inconclusive evidence for a continuing population decline. The oldest banded bird in North America lived for 11 years, 1 month, but another possibly lived for 15 years, 8 months.

Cook Islands

For the Cook Islands, the period July 2001 to June 2002 was dominated by continued population decline, unpopular political party switches by members of parliament, cabinet shuffles and reshuffles, dengue fever, flooding, ten-year high inflation, land controversies, and immigration concerns. Political events in the country's capital, Rarotonga, marked a year of major challenges for its democratically elected government, great political and reorganization disappointments, and a few guarded economic successes.

Consensus versus Conservation in the Upper Colorado River Basin Recovery Implementation Program

Abstract: We examined consensus‐based management through the lens of the Colorado River Recovery Implementation Program, a consensus‐based plan that attempts to develop the Colorado River's water while protecting its endangered fishes. Because this management model has been touted as a preferred substitute to government‐imposed regulation, we analyzed the recovery implementation program to determine its strengths and weaknesses. By reviewing secondary information and interviewing members of the diverse groups involved in the program, we gathered detailed information about the program's history, implementation, and progress. Our investigation revealed that the recovery implementation program has allowed development of the Colorado River's water and incorporated more voices into the decision‐making process. But the program circumvented federal authority over endangered species conservation, which has proved detrimental to the fishes. Furthermore, we learned that the consensus‐based model is vulnerable to control by special‐interests and may be driven by bureaucratic procedural goals rather than species recovery. To ameliorate these concerns, (1) program success should be judged by species recovery, rather than political achievements, (2) the federal government should retain the power of issuing statutory sanctions in the event of continued population decline, and (3) funding should be provided by an agency with a clear species‐protection agenda to reduce the disproportionate power of utilitarian interest groups. By incorporating these recommendations, conservation programs can better realize the benefits of a consensus‐based approach without sacrificing species recovery.

Moscow

Abstract Moscow is one of the largest capital cities in the world, and one with a longstanding legacy of city planning. The city has an imposing physical presence and vitality. In the 1990s city planning for Moscow has had to adapt to the collapse of the Soviet system, meet public expectations of more democratic processes, and meet the demands of a free market economy. This article examines the significance of the Soviet legacy, recent changes in the legal, administrative and urban governance framework for planning, and strategic planning issues facing the metropolis. After a preoccupation for decades of trying to restrain the growth of Moscow, its planners are now attempting to address the prospect of continued population decline and other urban issues which are now characteristic of large capitalist cities. The article concludes that Moscow is at a critical turning point, moving from being a socialist to a capitalist city.

The Continuing Population Decline of Torreya taxifolia Arn.

SCHWARTZ, M. W. (Illinois Natural History Survey, Champaign, IL 61820) AND S. M. HERmANN (Tall Timbers, Inc., Tallahassee, FL 32312). The continuing population decline of Torreya taxifolia Am. Bull. Torrey Bot. Club 120: 275-286. 1993.-Torreya taxifolia is a federally endangered dioecious conifer endemic to ravine bluffs along the east side of the Apalachicola River in Gadsden and Liberty Counties, Florida and Decatur County, Georgia (plus one outlying population in Jackson County, Florida). Torreya taxifolia experienced a catastrophic population decline, presumably fungal in origin, in the late 1950's. Within 10 years virtually no adults remained in the wild, a situation that persists to the present. Size measurements of trees indicate that the mean length of the longest stem is less than one meter. In a census population of over 100 trees, 10% died in four years, mostly from small size classes. Extension of terminal buds along the primary stem was infrequent, with only 47% of all trees experiencing any growth in length during the four year census period. With 32% of all trees losing their primary stem during the census interval, the mean size of individuals within the population is decreasing. Most individuals are multi-stemmed and continue to carry symptoms of disease. Although no causative agent for the decline has been identified, the most prevalent symptoms of disease are needle spots, needle necrosis and stem cankers. Growth fate does not appear to be strongly related to habitat or the incidence of disease symptoms, although stem mortality was higher among trees with heavy foliar pathogen loads. With no sexually mature trees and no seed production, this species faces continued decline.

Condition and Diet of Cycling Populations of the California Vole, Microtus californicus

Populations of the California vole, Microtus californicus, were followed at two sites near San Francisco Bay in order to investigate changes in diet and condition of these cycling microtine rodents. Mark and recapture analyses provided information on condition during seasonal (season to season) and annual (year to year) fluctuations, and snap trapping provided stomach samples for dietary analyses and carcasses for determinations of reproductive condition and fat reserves. Seasonal changes in condition were found to be correlated with dietary changes. The end of the breeding season in late spring was associated with low growth rates, low survival rates, and low fat reserves. At the same time the vegetation was drying, and the diet changed from one dominated by grass stems and leaves to one dominated by grass seeds. Breeding and adult growth sometimes began before the autumn rains while grass seeds were still the major dietary item, but occasional meals of green forbs and perennial grass were also taken at this time. Three annual grasses, Lolium multiflorum, Avena fatua, and Bromus rigidus, were preferred foods and formed the bulk of the winter diet at both low and high populations. The standing crop and seed production of these grasses were severely reduced by high vole populations. Reduction in food availability and quality might have caused the delay in the start of the breeding season, the low fat reserves and the continued population decline that were observed after the peak population. These results indicated that nutritive factors could be involved in microtine population cycles at low latitudes and point to the need for further research on diet quality and nutritional physiology of Microtus.