bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential Effects of Climatic Change on a Neotropical Migrant Landbird
Authors: RODENHOUSE NICHOLAS L.
Published: March 2003

Abstract: Significant climatic changes due to the “greenhouse” effect are predicted to occur in breeding and Wintering areas of neotropical migrant landbirds within 50 years. A simulation model was used to quantitatively evaluate the impact of predicted climatic changes on the annual productivity (number of fledgling · pair−1 season−1) of Blackthroated Blue Warbllers (Dendroica caerulescens). breeding in northern hardwoods forests. Results suggested that where mean summer rainfall increases by 20%, greater egg and nestling mortality may reduce annual breeding productivity by as much as 26%. Warmer temperatures however, will tend to enhance food abundance for insectivorous birds and lengthen the avian breeding season. These changes will act to increase breeding productivity, but they can only compensate for about a 10% increase in precipitation. Precipitation, however, is predicted to decline over most of the range of Black‐throated Blue Warblers. Where mean temperature is warmer and average summer precipitation is lower by as little as 10%, breeding productivity of Black‐throated Blue Warblers may be enhanced by up to 25%. Because significant regional differences in climatic change are likely, and because migratory bird species will differ in their response to climatic change, the emphasis of avian research should be on intensive regional studies of the factors influencing avian reproduction and survival.
Hereditary Blindness in a Captive Wolf (Canis lupus) Population: Frequency Reduction of a Deleterious Allele in Relation to Gene Conservation
Authors: Laikre Linda , Ryman Nils , Thompson Elizabeth A.
Published: March 2003

Numerous cases of hereditary diseases and disorders have been reported in wild animals bred in captivity, but little attention has been paid to the particular genetic management problems that arise when such defects occur. These problems include the obstacle of eliminating the deleterious allele(s) without contemporary loss of genetic variability. In this paper we use the statistical methods of pedigree analysis to address questions regarding a previously presumed hereditary form of blindness observed in a captive wolf population bred for conservation purposes in Scandinavian zoos. The most likely mode of inheritance coincides with an autosomal recessive allele with either a full penetrance or a reduced penetrance of 0.6 (depending on the reliability of studbook records). Using these two models of inheritance, we calculate the probability of carrying the blindness allele for each living animal. Analysis of the effect of removing high‐probability carriers on founder allele survival and level of inbreeding demonstrates that the frequency of the deleterious allele can be significantly reduced without seriously affecting founder allele survival or current degree of inbreeding in the wolf population.
Fish Faunas of the African Great Lakes: Origins, Diversity, and Vulnerability
Authors: Lowe‐McConnell Rosemary H.
Published: March 2003

The largest African Great Lakes, Tanganyika, Malawi, and Victoria, which have the richest lacustrine fish faunas of any of the world’s lakes, provide a unique comparative series for studies of evolutionary mechanisms, community ecology, and fish behavior. Their colorful littoral fishes are also known to aquarists worldwide. This paper examines the origins of their fish diversity, looking at the history of the lakes, colonization from river systems, and evolution of endemic faunas within each lake. All three lakes support fisheries of great socioeconomic importance for the rapidly rising human populations. The paper also examines the vulnerability of the faunas to fishing pressures and introductions of exotic species. In Malawi and Victoria, bottom‐trawling has altered the cichlid species composition. The loss of an estimated 200 taxa of endemic cichlid species from Lake Victoria’s fauna, following introductions of exotic fishes (tilapias and predatory centropomid Lates) 40 years ago, stresses the need to protect the unique fish faunas in Lakes Tanganyika and Malawi.
Biodiversity of the Pelagic Ocean
Authors: ANGEL MARTIN V.
Published: March 2003

Abstract: This paper reviews knowledge of biodiversity in open ocean pelagic communities and discusses the possible causal factors for the patterns. The oceanic pelagic ecosystem is by far the largest on Earth and, although locally its assemblages may be as rich as many terrestrial ecosystems, its global diversity (at both a species and an ecosystem level) is low. There are latitudinal trends in pelagic species diversity similar to those in many terrestrial taxa. High species richness in the oceans, however, tends to be associated with regions of low productivity that lack strong seasonality in the production cycle. The richest zones occur at the boundaries between different types of oceanic water where different faunas are mixed together, but the geographical locations of these boundaries are unstable and shift seasonally by hundreds of kilometers. If high diversity is emphasized in the development of protocols for conservation, then not only will the oceans receive low priority in conservation and resource management, but the regions most important in terms of process will also be overlooked. The scales of oceanic systems are so large that the methodologies developed for terrestrial conservation and resource management are inapplicable. Biodiversity may be regarded as the principal criterion for developing management strategies, yet the links (if any) between the ecological processes in the ocean that play such an important role in global homeostasis remain poorly characterized. The basis for a predictive understanding of the interaction between diversity and ecological process can be greatly enhanced relatively inexpensively by systematically collating existing data and working up extant collections of material
Response of Early Successional Vertebrates to Historic Changes in Land Use
Authors: LITVAITIS JOHN A.
Published: March 2003

Abstract: Unlike other regions of North America, forested habitats in New England bave increased substantially in the past 100 years. The proportion of land in New Hampshire covered by forests was 47% in 1880 and 87% in 1980. This increase was largely the result of a region‐wide abandonment of farms and the subsequent colonization of these lands by second‐growth forests. I examined the sequence of farm abandonment, forest colonization and forest maturation that occurred in New Hampshire in relation to changes in the abundance and distribution of a group of forest mammals and birds that have undergone substantial declines. A modeled pattern of secondary succession resulted in the availability of approximately 195,000 ha of early seral habitats (10–25 years after abandonment) from 1905 to 1940. These habitats then mutured into closed‐canopy forests by about 1960. Concurrent to the loss of early successional habitats, populations of New England cottontails (Sylvilagus transitionalis) decreased from an apparent continuous distribution throughout 60% of New Hampshire to fragmented populations that occupy less than 20% of the state Bobacts (Felis rufus) responded functionally (S. transitionalis in diet: 1951–1954 = 43%, 1961–1964 = 10%) and numerically (mean annual harvest of bobcats: 1951–1954 = 350, 1965–1969 = 36) to changes in cottontail abundance. Eighteen of 26 species of migratory passerines that nest in the forests of northern New England also declined during the period their populations were monitored (1934–1987). Eight (44%) of the species that declined are associated with early successional habitats, and these species consistently exhibited population declines during the 1950s. The reduction of early successional species may be extended in space and time by current land uses that fragment and isolate patches of habitat. Ownership patterns of forest lands in New England (excluding Maine) reveal 88% private ownership with an average holding of 10 ha. This suggests that large tracts of early successional habitats will be restricted to industrial and state/national forests. Although even‐aged management of a portion of these forests may be prerceived as incompatible with area‐sensitive and interior species, clustering of clearcuts and maintaining large tracts of mature habitats could sustain diverse populations of forest vertebrates.
What Is Ecosystem Management?
Authors: Grumbine R. Edward
Published: March 2003

The evolving concept of ecosystem management is the focus of much current debate. To clarify discussion and provide a framework for implementation, I trace the historical development of ecosystem management, provide a working definition, and summarize dominant themes taken from an extensive literature review. The general goal of maintaining ecological integrity is discussed along with five specific goals: maintaining viable populations, ecosystem representation, maintaining ecological process (ie., natural disturbance regimes), protecting evolutionary potential of species and ecosystems, and accommodating human use in light of the above. Short‐term policy implications of ecosystem management for several groups of key actors (scientists, policymakers, managers, citizens) are discussed. Long‐term (> 100 years) policy implications are also reviewed including reframing environmental values, fostering cooperation, and evaluating success. Ecosystem management is not just about science nor is it simply an extension of traditional resource management; it offers a fundamental reframing of bow humans may work with nature.
Apparent Species Turnover, Probability of Extinction and the Selection of Nature Reserves: A Case Study of the Ingleborough Limestone Pavements
Authors: Margules C.R. , Nicholls A.O. , Usher M.B.
Published: March 2003

Plant species recorded from two surveys of the Ingleborough limestone pavements in the U.K. 11 years apart, in 1974/75 and 1985, are used to assess the performance of potential reserve networks over time. The minimum set of pavements needed to represent all nationally rare and uncommon species occurring on the pavements in 1974/75 is inadequate in 1985 because of a very high level of apparent turnover in species composition. The number of species lost or gained is not correlated with pavement area and the turnover has not resulted in an equilibrium number of species; overall more species were lost than gained. Even if this turnover is due only to observer bias, it is a real phenomenon when it comes to land use decision‐making and should be taken into account when planning reserve networks and developing conservation management strategies. A statistical model of extinction probability is derived by relating the variable “extinct or not in 1985” to frequency of occurrence in 1974/75 using logistic regression. This model is then used to predict that 18, 19, or 20 and 21 species will have become locally extinct by 1994, 1995, and 1996, respectively. The list of species from which these extinctions are likely to be drawn is supplied.
Wildlife Disease in U.S. National Parks: Historical and Coevolutionary Perspectives
Authors: Alonso Aguirre A. , Starkey Edward E.
Published: March 2003

Diseases of wildlife have significant management implications in a number of lands of the U.S. National Park Service due to increasing interactions between wildlife and domestic animals. We review the paleontology, history, and coevolution of infectious diseases in North American ungulates. We provide two examples related to bovine brucellosis in bison in Yellowstone National Park and lungworm‐pneumonia complex in bighorn sheep in several western national parks. These examples illustrate the difficulty of managing wild populations and their diseases in national parks and other protected areas. In some instances, human intervention may be justifiable in order to protect native populations, domestic animals, and humans from acquiring a disease.
Set‐Back Distances to Protect Nesting Bird Colonies from Human Disturbance in Florida
Authors: Rodgers James A. , Smith Henry T.
Published: March 2003

Breeding colonial waterbirds are particularly susceptible to human disturbance because of their high‐density nesting habits. Identified detriments to reproductive success include egg and nestling mortality, nest evacuation, reduced nestling body mass and slower growth, premature fledging, and modified adult behaviors. Fifteen species of colonial waterbirds nesting at 17 colonies in north and central Florida were exposed to three different human disturbance mechanisms (HDMs) in order to determine recommended set‐back (RS) distances for protecting these mixed‐species nesting assemblages. Both intraspecific and interspecific variation were observed in flushing response distances to the same human disturbance mechanisms. In general, colonial waterbirds exhibited greater average flush distances in reaction to a walking approach than to approaching motor boats. Recommended set‐back distances were estimated using a formula based on the mean plus 1.6495 standard deviations of the observed flushing distances plus 40 meters [X = exp (X + 1.6495X + 40)]. In general, a recommended set‐back distance of about 100 meters for wading bird colonies and 180 meters for mixed tern/skimmer colonies should be adequate to effectively buffer the sites we studies from human disturbance caused by approach of pedestrians and motor boats. We recommend follow‐up studies to test our model at other breeding colonies.
Effective Population Size in Winter‐Run Chinook Salmon
Authors: Hedrick Philip W. , Hedgecock Dennis , Hamelberg Scott
Published: March 2003

Winter‐run chinook salmon from the Sacramento River, California, is federally listed as endangered. Since 1989 there has been aprogram to augment the natural population by capturing adults, artificially spawning them, raising tine young and releasing the smolt. Here we estimate the effective population size of these captive‐raised fish, the natural run, and the combination of both groups over the three‐year period from 1991 to 1993. We find that the most appropriate estimate of the effective population size of the captive‐raised progeny is a variance estimate of effective population size standardized so that the number of released smolts returning to spawn was the same as the number of spawners used to produce the smolts originally. We have generated 10,000 random samples to simulate returns from these released progeny. The estimates of the effective population sizes in 1991, 1992, and 1993 were only 7.02, 19.07, and 7.74, respectively. We then determined limits on the effective population size of the natural run based on 0.1 and 0.333 of the run‐size estimates. Using estimates of the captive proportion of the run, the minimum estimates of the effective population size of the overall run for the three years were 21.9, 127.3, and 39.0, and the maximum estimates were 61.6, 401.0, and 108.7. It does not appear that the hatchery program has reduced the overall effective population size. The run sizes in each year are extremely low, however, and it is possible that fish will be lost from this run in one of the years in the immediate future, making reestablishment of a healthy run even more difficult.
Conserving Biological Diversity through Ecosystem Resilience
Authors: Walker Brian
Published: March 2003

Confusion over the term ecological redundancy (Walker 1992) requires that the concept be clarified in order to advance the developing theory that maintaining ecosystem function conserves biological diversity. The species approach to conserving biological diversity assumes that the species in trouble are already identified. The ecosystem approach attempts to deal with the problem of conserving all the species in an ecosystem, including those not yet known. This is best achieved by ensuring that the ecosystem continues to function approximately as it has by maintaining its essential structure. Ecosystem stability (the probability of all species persisting) is enhanced if each important functional group of organisms (important for maintaining function and structure) comprises several ecologically equivalent species, each with different responses to environmental factors. In this sense ecological redundancy is good because it enhances ecosystem resilience, but functionally important groups (guilds, functional types) that have only one or very few species deserve priority conservation attention because their functions could be quickly lost with species extinctions.
A Diverse and Endangered Aquatic Ecosystem of the Southeast United States
Authors: Lydeard Charles , Mayden Richard L.
Published: March 2003

We document the biodiversity and conservation status of an extraordinarily diverse and endangered ecosystem in the United States that has failed to attract the same attention as tropical ecosystems—the rivers and streams of Alabama and adjoining states. Relative to North America as a whole, Alabama is a highlight of aquatic diversity supporting 38% of native fresh water fishes, 43% of native freshwater gill‐breathing snails, 60% of native mussels, and 52% of native freshwater turtles. Of these, 41%, 77%, 34%, and 22% of the fishes, snails, mussels, and turtles, respectively, are endemic to Alabama and an adjacent state. Like many tropical systems of developing nations, this fauna is in an imperiled state, with 10%, 65%, 69%, and 43% of Alabama’s fishes, gill‐breathing snails, mussels, and turtles, respectively, considered either extinct, endangered, threatened, or of special concern. Unlike tropical systems, however, little effort has been made to protect the taxa and their habitats. Only 40% of fishes, 1% of gill‐breathing snails, 32% of mussels, and 20% of freshwater turtles are formally listed as either threatened or endangered via the U.S. Endangered Species Act of 1973; no critical habitat has been protected. Clearly, the biodiversity crisis in not limited to tropical systems of developing nations. Although the Endangered Species Act of 1973 helps to ensure a future of sustainable diversity, efforts must be made to hasten recognition, protection, and recovery of critical habitat, particularly for hotspots such as the aquatic systems of Alabama.
Evaluating Causes of Population Change in North American Insectivorous Songbirds
Authors: Sauer John R. , Pendleton Grey W. , Peterjohn Bruce G.
Published: March 2003

Although the North American Breeding Bird Survey (BBS) is a principal source of information regarding populations of most North American bird species, many features of the survey complicate analysis of population change. Correlation studies based on BBS data cannot be used to define cause and effect relationships unambiguously. Recently, Böhning‐Gaese et al. (1993) presented an analysis of population trends in insectivorous songbirds using data from the BBS. They concluded that predation has played an important role in influencing population trends. We review aspects of the analysis methods for estimating population trends (e.g., observer effects, data subset) and for associating mean trends with species attributes (e.g., confounding of attributes). Using alternative analyses of the same BBS data, we demonstrate that the evidence that predation is associated with population declines is weaker than they suggested. Based on our analyses the only factor among those tested that was consistently associated with population trends was migration status (short‐distance migrant/resident versus long‐distance migrant) during the period 1978–1987. Also, we present evidence that the harsh winters of the mid‐1970s severely depressed populations of short‐distance migrant species and may have been responsible for the observed associations between migration status and population trends.
Resilience and Conservation of Large Carnivores in the Rocky Mountains
Authors: Weaver John L. , Paquet Paul C. , Ruggiero Leonard F.
Published: March 2003

Large carnivores evolved behaviors and life‐history traits that conferred resilience to environmental disturbances at various temporal and spatial scales. We synthesize empirical information for each large carnivore species in the Rocky Mountains regarding three basic mechanisms of resilience at different hierarchical levels: (1) behavioral plasticity in foraging behavior that ameliorates flux in food availability, (2) demographic compensation that mitigates increased exploitation, and (3) dispersal that provides functional connectivity among fragmented populations. With their high annual productivity and dispersal capabilities, wolves (Canis lupus) possess resiliency to modest levels of human disturbance of habitat and populations. Cougars (Puma concolor) appear to have slightly less resiliency because of more specific requirements for stalking habitat and lower biennial productivity. Grizzly bears (Ursus arctos horribilis) possess much less resiliency because of their need for quality forage in spring and fall, their low triennial productivity, and the strong philopatry of female offspring to maternal home ranges. Based upon limited information, wolverines (Gulo gulo) appear more susceptible to natural fluctuations in scavenging opportunities and may have lower lifetime productivity than even grizzly bears. By accelerating the rate and expanding the scope of disturbance, humans have undermined the resiliency mechanisms of large carnivores and have caused widespread declines. Both the resiliency profiles and the historical record attest to the need for some form of refugia for large carnivores. With their productivity and dispersal capability, wolves and cougars might respond adequately to refugia that are well distributed in several units across the landscape at distances scaled to successful dispersal (e.g., less than five home range diameters). With their lower productivity and dispersal capability, grizzly bears and wolverines might fare better in a landscape dominated by larger or more contiguous refugia. Refugia must encompass the full array of seasonal habitats needed by large carnivores and should be connected to other refugia through landscape linkages.
Avian and Mammalian Translocations: Update and Reanalysis of 1987 Survey Data
Authors: Wolf C. Magdalena , Griffith Brad , Reed Christine , Temple Stanley A.
Published: March 2003

In 1993 we conducted a follow‐up study of the 1987 survey by Griffith et al. (1989) of 421 avian and mammalian translocation programs in North America, Australia, and New Zealand to reassess the programs’ status and the biological and methodological factors associated with success. Our survey response rate was 81%. Approximately 38% of usable programs in 1993 reported a change in outcome from 1987 (e.g., a translocated population was “declining” but now is “self‐sustaining”), but the difference between the overall success rates was not statistically significant (66% in 1987 and 67% in 1993). Since 1987, an increase was observed in the median number of animals translocated per program (31.5 to 50.5), median duration of releases (2 to 3 years), and proportion of programs releasing more than 30 animals (46% to 68%). Multiple logistic regression analyses indicated that release into the core of the historical range, good‐to‐excellent habitat quality, native game species, greater numbers of released animals, and an omnivorous diet were positively associated with translocation success. Moreover, our results indicate that translocated birds were less successful at establishing self‐sustaining populations than translocated mammals. Our findings, using comparable logistic analyses, generally corroborate the results of Grifftth et al. (1989). Variables not found to be significantly correlated with translocation success include species’ reproductive potential (number of offspring and first age of reproduction), number and duration of the releases, and source of the translocated animals (wild‐caught versus captive‐reared).
Highly Differentiated Populations of the Narrow Endemic Plant Maguire Primrose (Primula maguirei)
Authors: Wolf Paul G. , Sinclair Robert B.
Published: March 2003

Maguire primrose (Primula maguirei) is a geographically restricted plant species, known only from a 19‐km stretch of Logan Canyon in northern Utah (U.S.A.). We examined variation at 13 isozyme loci from 25 individuals of P. maguirei at each of eight sites. At individual loci we detected no statistically significant deviations from Hardy‐Weinberg proportions within sites (subpopulations). However, some loci were almost fixed for different alleles at the upper reaches of the species’ range relative to populations approximately 10 km away. The total mean gene diversity among loci was 0.22, of which 55% was partitioned within subpopulations, 0.7% among subpopulations within populations (100 m spatial scale), 3% among populations separated by about 1 km, and 41% between an Upper Canyon group of populations and a Lower Canyon group (10‐km scale). We detected no gametic disequilibria among loci within subpopulations (and populations). Two hypotheses are proposed to explain the results: (1) past genetic bottlenecks and (2) genetic divergence as a by‐product of local adaptations to different habitats. Regardless of the causes of allozymic differentiation, our results suggest that plans for artificial establishment or reestablishment of P. maguirei populations should use source populations within 1 km of the establishment site. This study emphasizes the potential use of data on population genetic structure for managing and monitoring rare species.
Nesting Success of a Disturbance‐Dependent Songbird on Different Kinds of Edges
Authors: Suarez Andrew V. , Pfennig Karin S. , Robinson Scott K.
Published: March 2003

We compared the nesting success of a disturbance‐dependent species, the Indigo Bunting ( Passerina cyanea), on different kinds of habitat edges in five sites (225 total nests) in southern Illinois from 1989 to 1993. Nest predation rates along agricultural and abrupt, permanent edges (e.g., wildlife openings, campgrounds) were nearly twice as high as rates along more gradual edges where plant succession was allowed to occur (e.g., treefalls, streamsides, gaps created by selective logging ). Levels of brood parasitism by Brown‐headed Cowbirds ( Molothrus ater) varied significantly among sites and years, but not among edge types. Clutch sizes, however, were significantly smaller at agricultural edges where nest predation rates were also high, which suggests either decreased food availability or a population dominated by younger and/or lower‐quality ( poor condition) birds. The results of this study illustrate the need to reevaluate management practices (e.g., wildlife openings) that are designed to promote populations of disturbance‐dependent wildlife.
Endangered Species Legislation beyond the Borders of the United States
Authors: Ray Justina C. , Ginsberg Joshua R.
Published: March 2003

Note: This month's “Issues in International Conservation” was guest edited by Justina Ray who, with Associate Editor Joshua Ginsberg, presents an overview of some global trends in endangered species legislation.
Effects of Recreational Scuba Diving on Caribbean Coral and Fish Communities
Authors: Hawkins Julie P. , Roberts Callum M. , Van'T Hof Tom , De Meyer Kalli , Tratalos Jamie , Aldam Chloe
Published: March 2003

Abstract: Scuba diving on coral reefs is an increasingly lucrative element of tourism in the tropics, but divers can damage the reefs on which tourism depends. By studying the effects of diving we can determine what level of use is justifiable in balancing objectives of economic gain and conservation. Off the Caribbean island of Bonaire we compared coral and fish communities between undived reserves and environmentally similar dive sites where maximum use reached 6000 dives per site per year. At these levels of diving, direct physical damage to reefs was relatively minor. There were more loose fragments of living coral in dive sites than reserves and more abraded coral in high‐ than low‐use areas. Diving had no significant effect on reef fish communities. Between 1991 and 1994, diving intensity increased 70% and coral cover declined in two of three dive sites and in all three reserves, suggesting a background stress unrelated to tourism. There was a significant decline in the proportion of old colonies of massive coral species within dive sites (19.2% loss), compared to a smaller loss in reserves (6.7%). Branching corals increased by 8.2% in dive sites, compared with 2.2% in reserves. Despite close management of reefs, diving is changing the character of Bonaire's reefs by allowing branching corals to increase at the expense of large, massive colonies. The impact of background stresses on massive corals seems to have been greater in the presence of diving. Other studies have linked disease infection to coral tissue damage, and the higher rates of abrasion we recorded in dived sites could have rendered corals there more susceptible to disease, thus mediating the decline of massive corals. Our study shows that even relatively low levels of diving can have pronounced effects manifested in shifts in dominance patterns rather than loss of overall coral cover. Bonaire's reefs have among the highest coral cover and greatest representation of ancient coral colonies of reefs anywhere in the Caribbean. Conserving the character of these reefs may require tighter controls on diving intensity.
Fitness Decline under Relaxed Selection in Captive Populations
Authors: Bryant Edwin H. , Reed David H.
Published: March 2003

Abstract:
We compared life‐history schedules among populations of the housefly ( Musca domestica L.) maintained in the laboratory under curtailed life span, such that selection on mutations that affected only late‐life fitness traits was reduced. As a result of this regime, late‐life ( but not early‐life) fecundity declined within a few generations. The results suggest that if captive populations are maintained with minimal selection, either by direct manipulation of the environment or by equalizing family contributions, the increased frequency of potentially deleterious mutations may rapidly lower the ability of these populations to exist under natural conditions. This would be independent of population size, so expanding captive populations would not alleviate potential fitness reductions due to relaxed selection.
Selection of Islands for Conservation in the Urban Archipelago of Helsinki, Finland
Authors: Ranta Pertti , Tanskanen Antti , Niemelä Jari , Kurtto Arto
Published: March 2003

Abstract: The occurrence of vascular plants was surveyed on 207 islands (size range 0.01–390.2 ha, number of plant species 1–449) offshore from the city of Helsinki in the Baltic Sea to examine the conservation value of these islands. We calculated a rarity score for each species (1/number of islands occupied by the species) and a biodiversity score for each island (sum of the rarity scores of each species present on the island). Positive correlations between species number and biodiversity score (rs = 0.97, p < 0.001) and between biodiversity score and island area (rs = 0.87, p < 0.001) indicated that these parameters are heavily dependent on island size. With the goal of including at least one occurrence (island) of all plant species, an iterative selection algorithm chose a set of 41 islands whose average size (29.3 ha) was four times the average size of all existing islands (7.0 ha). Strong nestedness ( N < 54) explains the concentration of plant species diversity on large islands. An operational strategy for selection of sites for protection is to complement the set produced by a selection algorithm with target species not yet included (e.g., endangered species with several occurrences). Comprehensive mapping and analysis of a taxonomic group will help integrate conservation biology into land‐use planning and increase the quality of the networks of protected areas.
Combining Power Analysis and Population Viability Analysis to Compare Traditional and Precautionary Approaches to Conservation of Coastal Cetaceans
Authors: Thompson Paul M. , Wilson Ben , Grellier Kate , Hammond Philip S.
Published: March 2003

Abstract: Traditionally, marine resources have been managed such that controls on new developments are implemented only when harmful effects on other environmental or economic interests can be demonstrated. This approach poses particular problems for the conservation of coastal cetaceans because potential threats to their populations are diverse and likely to interact, individual threats may result from multiple sources, and the problems inherent in studying cetaceans result in considerable scientific uncertainty and low statistical power to detect any effects. Consequently, many countries are adopting integrated coastal management programs and precautionary management principles. In practice, however, issues continue to be dealt with within traditional frameworks that require demonstration of harm. Because cetaceans are long‐lived, they demand long‐term studies, and populations could decline to dangerously low levels before management action is taken. We illustrate these problems using a case study from the Moray Firth, Scotland. This inshore area will soon be designated and managed as a “special area of conservation” to protect bottlenose dolphins (  Tursiops truncatus) under the European Community's Habitats Directive. The population is small and isolated, and it faces a wide range of potential threats, but there remains considerable uncertainty over the magnitude of each threat. We combined power analysis and population viability analysis to explore the relative consequences of adopting either traditional or precautionary approaches to management. In this case, our results reaffirm the need for precautionary management. More generally, we illustrate how this approach can be used to provide a more scientific basis for determining the level of precaution required to address particular management issues in this and other marine systems.
Demographic Approach to Releasing Adults versus Young in Reintroductions
Authors: Sarrazin François , Legendre Stéphane
Published: March 2003

Abstract: Reintroductions are often used for reestablishment of animal populations. The choice of age‐class of released individuals, however, is often arbitrary or based on expediency. We developed a demographic model that predicts the relative efficiency of releasing juveniles or adults for a given life cycle. The model accounts for possible reduction of survival and fertility of released adults. It also incorporates demographic and environmental stochasticity to compare release strategies of varying duration and number of releases. We applied the model to the case of reintroduction of Griffon Vultures (Gyps fulvus) in southern France, for which accurate monitoring allowed us to estimate demographic rates and consequences of releases. Overall, for Griffon Vultures, it is more efficient to release adults than juveniles, despite the observed reduction of demographic parameters following release. This approach could be used for the reintroduction of other species.
A Survey and Overview of Habitat Fragmentation Experiments
Authors: Debinski Diane M. , Holt Robert D.
Published: March 2003

Abstract: Habitat destruction and fragmentation are the root causes of many conservation problems. We conducted a literature survey and canvassed the ecological community to identify experimental studies of terrestrial habitat fragmentation and to determine whether consistent themes were emerging from these studies. Our survey revealed 20 fragmentation experiments worldwide. Most studies focused on effects of fragmentation on species richness or on the abundance(s) of particular species. Other important themes were the effect of fragmentation in interspecific interactions, the role of corridors and landscape connectivity in individual movements and species richness, and the influences of edge effects on ecosystem services. Our comparisons showed a remarkable lack of consistency in results across studies, especially with regard to species richness and abundance relative to fragment size. Experiments with arthropods showed the best fit with theoretical expectations of greater species richness on larger fragments. Highly mobile taxa such as birds and mammals, early‐successional plant species, long‐lived species, and generalist predators did not respond in the “expected” manner. Reasons for these discrepancies included edge effects, competitive release in the habitat fragments, and the spatial scale of the experiments. One of the more consistently supported hypotheses was that movement and species richness are positively affected by corridors and connectivity, respectively. Transient effects dominated many systems; for example, crowding of individuals on fragments commonly was observed after fragmentation, followed by a relaxation toward lower abundance in subsequent years. The three long‐term studies (14 years) revealed strong patterns that would have been missed in short‐term investigations. Our results emphasize the wide range of species‐specific responses to fragmentation, the need for elucidation of behavioral mechanisms affecting these responses, and the potential for changing responses to fragmentation over time.
Applying Metapopulation Theory to Conservation of Migratory Birds
Authors: Esler Daniel
Published: March 2003

Abstract: Metapopulation theory has proven useful for understanding the population structure and dynamics of many species of conservation concern. The metapopulation concept has been applied almost exclusively to nonmigratory species, however, for which subpopulation demographic independence—a requirement for a classically defined metapopulation—is explicitly related to geographic distribution and dispersal probabilities. Defining the degree of demographic independence among subpopulations of migratory animals, and thus the applicability of metapopulation theory as a conceptual framework for understanding population dynamics, is much more difficult. Unlike nonmigratory species, subpopulations of migratory animals cannot be defined as synonymous with geographic areas. Groups of migratory birds that are geographically separate at one part of the annual cycle may occur together at others, but co‐occurrence in time and space does not preclude the demographic independence of subpopulations. I suggest that metapopulation theory can be applied to migratory species but that understanding the degree of subpopulation independence may require information about both spatial distribution throughout the annual cycle and behavioral mechanisms that may lead to subpopulation demographic independence. The key for applying metapopulation theory to migratory animals lies in identifying demographically independent subpopulations, even as they move during the annual cycle and potentially co‐occur with other subpopulations. Using examples of migratory bird species, I demonstrate that spatial and temporal modes of subpopulation independence can interact with behavioral mechanisms to create demographically independent subpopulations, including cases in which subpopulations are not spatially distinct in some parts of the annual cycle.
Edge Effects on the Understory Bird Community in a Logged Forest in Uganda
Authors: Dale Svein , Mork Kjetil , Solvang Rune , Plumptre Andrew J.
Published: March 2003

Abstract: Understanding how the fauna of logged tropical rainforests responds to fragmentation and the creation of edges is vital to ensure conservation of biodiversity. We studied the composition of the understory bird community from the edge of a 15‐ha clearing toward the interior of the forest in a part of Budongo Forest Reserve, Uganda, that was selectively logged about 45 years ago. Mist netting was conducted along five transects from the edge and 500 m into the interior. The total number of individuals captured did not change with distance from the edge, but there was a significant increase in the number of species. We sampled fewer, but more common species near the edge, whereas the interior of the forest had more, and less common species. Guild composition also changed with distance from the edge. Frugivore‐insectivores and nectarivores were most common close to the edge. Among insectivores, ground foragers, bark‐gleaners, and leaf‐gleaners were most common in the interior of the forest, whereas sallying insectivores favored the edge. Graminivores were unaffected by the edge. Analysis of common species showed that Ispidina picta, Andropadus curvirostris, A. latirostris, Camaroptera brachyura, Terpsiphone rufiventer, and Nectarinia olivacea were associated with the edge, but no species showed significant avoidance of the edge. This finding may be explained by the generally low sample sizes of interior species. Our results show that even bird communities in logged forests respond to edges. Estimates of edge effects suggested that changes in bird densities may have occurred several hundred meters from the edge. In conclusion, logged forests provide habitat for bird species avoiding forest edges, and this should be considered in the management of such forests for conservation.
Use of Premontane Moist Forest and Shade Coffee Agroecosystems by Army Ants in Western Panama
Authors: Roberts Dina L. , Cooper Robert J. , Petit Lisa J.
Published: March 2003

Abstract: Two species of Neotropical army ant, Eciton burchelli and Labidus praedator ( Hymenoptera: Formicidae: Ecitoninae), are swarm‐raiding species that require large areas of habitat in which to hunt. Behavioral and distributional studies of these two species have been confined largely to humid lowland forest. We conducted intensive systematic area searches at elevations between 1200 and 1800 m in western Panama to assess the distribution of both species in intact premontane moist forest, shade coffee plantations, and sun coffee plantations. Both species were repeatedly observed in forest, shade coffee plantations close to forest, and shade coffee plantations distant from forest. Neither species was observed in sun coffee plantations. We believe that retention of certain forest‐like characteristics in the traditional shade coffee farm contributes to the persistence of these forest organisms in modified landscapes. Large canopy trees not only provide shade that buffers temperature extremes but also supply the ground layer with regular inputs of leaf litter and coarse woody debris from fallen trunks. Both E. burchelli and L. praedator hunt in leaf litter, and E. burchelli uses coarse woody debris as nesting sites ( bivouacs). There were significantly fewer potential bivouacs available in sun coffee plantations than in forest and shade coffee habitats. Also, litter depth was less in sun coffee than in forest and shade coffee. Our results provide the first evidence that shade coffee plantations can provide additional habitat for E. burchelli and L. praedator, top predators of the leaf litter arthropod community. E. burchelli and L. praedator act as critical links between swarm‐attendant bird species and leaf‐litter arthropods, providing an easily exploited food resource that would otherwise be unavailable for many birds. Continued conversion of shade coffee plantations to sun coffee plantations could have negative effects on army ants and associated biodiversity.
Response Time of Wetland Biodiversity to Road Construction on Adjacent Lands
Authors: T Findlay C. Scot , Bourdages Josée
Published: March 2003

Abstract: Road construction may result in significant loss of biodiversity at both local and regional scales due to restricted movement between populations, increased mortality, habitat fragmentation and edge effects, invasion by exotic species, or increased human access to wildlife habitats, all of which are expected to increase local extinction rates or decrease local recolonization rates. Species loss is unlikely to occur immediately, however. Rather, populations of susceptible species are expected to decline gradually after road construction, with local extinction occurring sometime later. We document lags in wetland biodiversity loss in response to road construction by fitting regression models that express species richness of different taxa ( birds, mammals, plants, and herptiles) as a function of both current and historical road densities on adjacent lands. The proportion of variation in herptile and bird richness explained by road densities increased significantly when past densities were substituted for more current densities in multiple regression models. Moreover, for vascular plants, birds, and herptiles, there were significant negative effects of historical road densities when the most current densities were controlled statistically. Our results provide evidence that the full effects of road construction on wetland biodiversity may be undetectable in some taxa for decades. Such lags in response to changes in anthropogenic stress have important implications for land‐use planning and environmental impact assessment.
Demography of the California Condor: Implications for Reestablishment
Authors: Meretsky Vicky J. , Snyder Noel F. R. , Beissinger Steven R. , Clendenen David A. , Wiley James W.
Published: March 2003

Abstract: The remnant wild population of California Condors (Gymnogyps californianus) of the 1980s exhibited a rapid population decline caused by high mortality rates among adult and immature birds. The most prominent mortality factor was lead poisoning resulting from ingestion of bullet fragments in carcasses. Successful captive breeding has allowed many birds to be released to the wild since 1992, based originally on an assumption that exposure to lead could be prevented by food subsidy. The mortality of released birds, however, has generally exceeded levels needed for population stability calculated from simple population models. Collision with overhead wires was the most frequent cause of death in releases before 1994. Lead poisoning again surfaced as a problem starting in 1997 as older birds began feeding on carcasses outside the subsidy program. Although poisonings have been treated successfully by chelation therapy in recaptured birds, food subsidy is proving an ineffective solution to lead exposure. The best long‐term solution appears to be either the creation of large reserves where hunting is prohibited or the restriction of hunting to nontoxic ammunition in release areas. Until sources of lead contamination are effectively countered, releases cannot be expected to result in viable populations. In addition, problems involving human‐oriented behavior have resulted in the permanent removal of many released birds from the wild. The most promising reduction in human‐oriented behavior has been achieved in one release of aversively conditioned, parent‐reared birds. Rigorous evaluation of the factors reducing attraction to humans and human structures has been hampered by confounding of techniques in releases. Behavioral problems could be more quickly overcome by adoption of a comprehensive experimental approach.