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Relation of environmental factors to breeding status of royal and sandwich terns in South Carolina, USA
The population ecology of the royal tern Sterna maxima and sandwich tern Sterna sandvicensis was investigated in South Carolina from 1970 through 1977. Royal and sandwich terns nested together in all of the colonies that we located. The peak in egg laying usually occurred in early May; peak hatching occurred from late May to mid-June. Clutch size for both species was one egg. Tidal flooding was the major factor in egg loss. The breeding population was 15,499 pairs in 1974 and 18,096 pairs in 1975; sandvicensis made up about 5% of the breeding population. The average number of young fledged per nest ranged from 0·36 to 0·44. Residues of organochlorine pollutants in most eggs and tissues were low and posed no identifiable threat to the terns. There was a decline in DDE and dieldrin residues in eggs of maxima . The future of royal and sandwich terns in South Carolina seems fairly secure as the population is apparently at or near carrying capacity and most of the major nesting sites are dedicated to protection of nesting birds.
Distribution and status of Vicia menziesii Spreng. (Leguminosae): Hawai'i's first officially listed endangered plant species
Vicia menziesii Spreng., Hawai'i's first officially listed endangered plant species, formerly occurred across a large area in the upper montane-mesic forest habitat on the windward side of the island of Hawai'i. Until this species was ‘rediscovered’ in 1974, it had last been seen in 1915, and it was presumed to be extinct. The population is presently thought to number 150–300 plants, most of which are seedlings. These are located within a 200 ha area on the eastern flank of Mauna Loa volcano. The primary factors responsible for the decline of V. menziesii are habitat loss and excessive predation on the plants by introduced ungulates. Continued logging and cattle grazing within its remnant range are major threats to its existence. Enhancing the survival of V. menziesii may best be accomplished by stabilizing its remaining habitat and allowing the population to reestablish itself naturally.
Status of the West Indian manatee in Honduras
Aerial surveys and interviews with fisherman in Honduras indicate that manatee numbers are low. There is an abundance of suitable habitat, and evidence on the proportion of calves indicates that manatees are reproducing. Although natural mortality occurs when the animals are trapped in small landlocked coastal lagoons, the greatest threat to manatees is from subsistence hunting for their meat. Harpooning from a small motorised canoe is the most common means of capture; however, entanglement in gill nets may also be employed. Enforcement of existing protective laws and enlistment of public support is required to preserve the remaining manatees in Honduras.
Tolerance of West Indian manatees to capture and handling
Ninety-two West Indian manatees (Trichechus manatus) have been captured in the southeastern United States from October 1975 through November 1983 with no evidence of an unusual susceptibility to capture myopathy. Of these, 53 were radio-tracked or observed in the field following capture with no evidence of delayed capture stress. Blood samples obtained at capture for 20 wild individuals displayed no elevation in biochemical variables typically seen in mammalian capture myopathy cases. Thirty-one manatees captured for rescue and rehabilitation generally did not exhibit symptoms of capture myopathy, although in one case marked elevations in creatinine phosphokinase were observed, probably related to lengthy transport. Necropsy findings for 20 terminal cases that died of various causes unrelated to their rescue or handling did not indicate the involvement of any gross or histological lesions of capture myopathy. Historical records for the capture and handling of about 150 West Indian manatees during the 1900s also suggest a tolerance to these activities. Recent observations on the probable susceptibility of dugongs (Dugong dugon) to capture stress apparently cannot be extended to West Indian manatees.
Colony site selection and abandonment by least terns Sterna antillarum in New Jersey, USA
To develop habitat and management procedures to protect declining populations of least terns, colony site selection and abandonment by this species was investigated at 26 sites in New Jersey. Multivariate analysis was used to compare (1) colony sites to adjacent unused areas, (2) those located on beaches to dredge spoil sites and (3) abandoned to occupied colony sites. The presence of shells or pebbles in a sandy substrate, and short, sparse vegetation, were the habitat characteristics of New Jersey least tern colony sites most strongly correlated with colony site selection. Dredge spoil sites had significantly greater evidence of human disturbance, distance to water, and proportion of coarse particles in the substrate than beach sites. These differences may have contributed to the smaller colonines and greater colony turnover rates at spoil sites relative to beach sites. Overall, abandoned colony site characteristics did not differ significantly from occupied sites. However, human disturbance, over-growth of vegetation, predation, and flooding were all prevalent at colonies prior to abandonment. The results of this study suggest techniques for habitat management of both least and little terns.
Distribution, status, and traditional significance of the West Indian manatee Trichechus manatus in Venezuela
Aerial and interview surveys were conducted in 1986 to determine the current distribution, status, and traditional significance of the West Indian manatee Trichechus manatus in Venezuela. Aerial surveys provided just eight tentative sightings in 73 hours of searching. These discouraging results may have been due to poor visibility, small populations, and perhaps reduced dry season manatee activity. Results of interview surveys, however, permitted a number of important generalizations. A remnant manatee population exists in Lake Maracaibo, but none occur along the more than 1500 km of Caribbean coastline. Abundance is greatest in eastern Venezuela bordering the Golfo de Paria, in the Orinoco Delta, and in the middle Orinoco and tributaries. Local market hunting in the middle of this century probably greatly reduced manatee populations in these areas. Recent protection laws, education efforts, and manatee scarcity have resulted in a declining interest in manatee hunting. Much excellent manatee habitat persists in these regions, and a continued decline in hunting could result in an optimistic outlook for future manatee populations if the incidental take in net fisheries is controlled. Traditional beliefs and legends concerning manatees in Venezuela, including hunting taboos, show that these animals remain a colorful part of the folk culture. However, manatee protection does not pose economic hardships or infringe upon traditional spiritual beliefs.
Northern Alabama colonies of the endangered grey bat Myotis grisescens: organochlorine contamination and mortality
From 1976 to 1986, dead and dying grey bats Myotis grisescens and grey bat guano were collected from caves along the Tennessee River in northern Alabama to determine the possible role of organochlorine chemicals — in particular wastes from a former DDT manufacturing plant near Huntsville—in the mortalities. Concentrations of chemical residues in brains were less than known lethal levels; certain observations and analyses did indicate the possibility of past organochlorine-induced bat deaths. Levels of contaminants in bats declined slowly during the 10-year sampling period, but heavy residue burdens persist. The high ratio of DDD to DDE in residues from the former DDT plant made them identifiable as far as 140 km downriver. Grey bats concentrated chemical residues to higher levels and demonstrated the presence of these residues over much greater distances than did red-winged blackbirds Agelaius phoenicus . Grey bats may be the most sensitive indicator available for monitoring the contamination from this former DDT manufacturing site.
Population trends of North American shorebirds based on the International Shorebird Survey
Shorebirds Charadrii are prime candidates for population decline because of their dependence on wetlands that are being lost at a rapid pace. Thirty-six of the 49 species of shorebirds that breed in North America spend most of the year in Latin America. Because populations of most species breed and winter at remote sites, it may be most feasible to monitor their numbers at migration stopovers. In this study, we used statistical trend analysis methods, developed for the North America Breeding Bird Survey, to analyze data on shorebird populations during southbound migration in the United States. Survey data were collected by volunteers in the International Shorebird Survey (ISS). The analyses indicate that whimbrels Numenius phaeopus , short-billed dowitchers Limnodromus griseus , and sanderlings Calidris alba have undergone statistically significant declines. Methodological concerns over both the ISS and the trend analysis procedures are discussed in detail and biological interpretations of the results are suggested.
Vegetation alteration along trails in Shenandoah National Park, Virginia
Most studies in the USA of vegetation alteration and human impact along trails have been located in large western wilderness areas. The objective of this study was to determine vegetation changes occurring along trails in an eastern ecosystem supporting second-growth deciduous forest. The location of this study was Shenandoah National Park in Virginia, which has a long history of trail use by humans. Located in different sections of the park, ten trails were chosen as study areas. In each, transects were established to measure ground flora in trailside, transition, and undisturbed areas perpendicular to the trail. Field data were collected on frequency, life-form, and percent cover for ground flora of 25 cm or less in height. Cover and species diversity increased toward the trail in eight out often cases. Competition for light and resistance to trampling were thought to influence the occurrence of plants along the transect. Plants found along the trail border were represented by low growthforms, early blooming, or graminoid characteristics, and hemicryptophyte, therophyte, or chamaephyte life-forms. Plants found in the undisturbed zone were represented by scattered cover and frequency, woody growth forms or delicate herbaceous forms, and phanerophyte or geophyte life-forms.
Effects of habitat fragmentation on a stream-dwelling species, the flattened musk turtle Sternotherus depressus
The flattened musk turtle Sternotherus depressus has disappeared from more than half of its former range because of habitat modifications to stream and river channels in the Warrior River Basin, Alabama. Only 6·9% of its probable historic range contains relatively healthy populations, and most populations are fragmented by extensive areas of unsuitable habitat. Turtles in the best remaining habitats continue to be vulnerable to disease and human-related disturbance, collecting and habitat modification. These factors lead to population declines and abnormal population structure. Habitat fragmentation, especially in small populations, increases vulnerability to human-caused catastrophes and demographic accidents, and could lead to eventual extinction. The threats facing fragmented populations of this turtle probably parallel those affecting many other stream-dwelling species throughout the southeastern United States.
Breeding biology of the spotted salamander Ambystoma maculatum (Shaw) in acidic temporary ponds at Cape Cod, USA
The relationship between water chemistry and breeding success of spotted salamanders Ambystoma maculatum (Shaw) was examined in temporary woodland ponds on outer Cape Cod, Massachusetts in 1985 and 1986. Most pond waters were dilute (3median coductivity = 57 umhos cm −1 (1 umhos cm −1 = 0·1 mSm −1 )), acidic (median pH = 4·82), and highly colored (median = 140 Pt-Co units). Most acidity was due to abundant organic acids. Salamander survival to hatching was over 80% at 8 of 12 ponds monitored. Complete mortality, preceded by gross abnormalities, was observed only among embryos in the most acidic spawning pond (pH 4·3−4·5) in both years. Embryo transfers between ponds and laboratory studies indicated that reduced survival was due to the interaction of low pH with high tannin-lignin concentration. The use of amphibian embryonic survival to indicate acid rain effects is complicated by multiple habitat parameters and should only be attempted in conjunction with long-term population monitoring.
The status of the Red Hills salamander Phaeognathus hubrichti, Alabama, USA, 1976–1988
A total of 144 sites in the Red Hills Physiographic Province in south-central Alabama, USA, were surveyed in 1988 for burrows of the Red Hills salamander Phaeognathus hubrichti . Of 92 sites surveyed in 1976, no change occurred in the habitat at 54 sites, conditions improved at 19 sites and deteriorated at 18 sites following selective or clear cutting. An additional 14 of 52 sites not surveyed in 1976 were adversely affected by logging. Burrows were most often found on high ( x ̄ = 17 m "> x̄= 17 m ), steep ( x ̄ = 50° "> x̄= 50° ), uncut slopes containing a high soil moisture content ( x ̄ = 57% "> x̄= 57% ) and full tree canopy. Slope angle and soil pH did not affect burrow abundance. Burrow openings averaged 10·9 mm high × 15·3 mm wide. Burrow angle was negatively correlated with burrow width and slope angle but low r 2 values indicate that little of the variation was explained by these variables. Burrows were most often found on the upper two-thirds of slopes; burrows on slopes affected by cutting were found in the middle of the slope where they were less prone to disturbance and desiccation. Although most timber companies claim to no longer cut steep slopes in order to protect salamanders, detrimental forestry practices are still occuring. In some instances, Red Hills salamanders survive selective and clear cutting, but the persistence and viability of affected populations remain unknown. Suggestions are made to reduce impacts from forestry operations. Acquisition of 25 sites containing viable salamander populations and retention as a threatened species under United States federal law are recommended.
Movements of Yellowstone grizzly bears
Ninety-seven grizzly bears Ursus arctos horribilis were radio-located 6299 times during 1975–1987. Annual range sizes differed by sex, age, reproductive status and amount of precipitation. Females exhibited greater fidelity to seasonal and annual ranges than males. Weaned female offspring generally remained in the vicinity of the maternal range, while weaned males often made substantial movements to unexplored country. Average total home range size was 884 km 2 for females and 3757 km 2 for males. Males consistently exhibited greater indices of movement and range sizes than females. All cohorts had larger mean ranges during this study than during the period 1959–1969 when the population had access to open garbage dumps. Movements and elevational distribution of all cohorts were related to availability of whitebark pine Pinus albicaulis seeds. We hypothesized that females with cubs-of-the-year and yearlings were displaced from most productive habitats during seasons and years of limited food availability.
Disappearance of the cascades frog Rana cascadae at the southern end of its range, California, USA
It has recently become evident that amphibian species in many areas of the world have suffered serious declines. Healthy, seemingly well-protected populations have disappeared for no obvious reason. Data from historic accounts and museum records indicate that the Cascades frog, Rana cascadae , was once abundant at the southern end of its range in the vicinity of Lassen Volcanic National Park, California, USA. We conducted intensive searches at all 16 sites where R. cascadae had previously been recorded in the Lassen area, plus 34 additional sites with suitable habitat. Whereas earlier biologists could sometimes find 40 or more frogs at some of these sites, we were only able to locate two frogs at a single locality. This represents a precipitous decline over a period of <15 years. The decline seems to have been caused by a combination of local factors, including (1) the presence of non-native, predatory fish which have restricted habitat and limited dispersal of frogs; (2) loss of breeding habitat due to a five-year drought; and (3) the gradual loss of open meadows and associated aquatic habitats. The loss of frogs suggests that some common management practices in parks and wilderness areas may be endangering some of the species these areas are intended to protect. Similar local factors may account for amphibian declines reported elsewhere and should be carefully evaluated along with possible global effects.
Snaring to control feral pigs sus scrofa in a remote Hawaiian rain forest
Feral pig Sus scrofa control in Kipahulu Valley, a remote rain forest in Haleakala National Park, Maui, Hawaiian Islands, has been achieved with snares over a 45-month period. Initial pig densities in fenced management units of 6·2 km 2 and 7·8 km 2 were estimated at 6 animals/km 2 and 14·3 animals/km 2 for the two units, based on population reconstruction from animals killed and aged. During the 45 months of the study, 1978 snares were set, and 1·6 million snare nights were logged. Snare density reached 96/km 2 and 200/km 2 for the two management units by the end of the study. A mean effort of 43 worker hours/pig was used to remove 53 pigs from the upper management unit, and a mean of 7 worker hours/pig to remove 175 animals from the more densely populated lower unit. Pig activity monitoring along transects provided a good measure of control effectiveness until densities of about 1 pig/km 2 were achieved, after which transects became less useful than scouting for determining pig activity.
Landscape change and its effects on the wintering range of a lesser snow goose Chen caerulescens caerulescens population: A review
The Texas coast has experienced considerable urban, industrial, and agricultural growth during the 20th Century. The region provides important wintering habitat to many avian species, including lesser snow geese Chen caerulescens caerulescens . This paper draws the biological and ecological fields into an historical perspective by examining available literature on the development of the upper Texas coast and range changes of lesser snow geese. Historically, lesser snow geese wintered in the coastal marshes, but expanded their range into the adjacent prairies in the mid-1900s. Winter range expansion was negatively affected by urban and industrial encroachment in the coastal marshes and positively influenced by agricultural development in the prairies, which increased dramatically during World War II. The lesser snow goose population flourished alongside some human-induced landscape alterations. However, projected declines in agriculture and increased urbanization of prairie and coastal marsh habitats may result in significant negative effects on the lesser snow goose population.