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Geology topics

J. R. Longcore

Publications and source records attributed to J. R. Longcore.

At least 55 records · Page 3Linked to original sources
USGS1989

Survival and movements of molting male black ducks in Labrador

We marked 26 flightless male American black ducks with transmitters during the post-nuptial molt in northern Labrabor to determine survival and movements. Twelve ducks remained in the watershed where marked and 11 ducks moved to different watersheds. The period survival rate (PSR) for these flightless males was 0.89 using the Kaplan-Meier estimator. Only 2 ducks were killed by predators. Death of these 2 ducks might have been influenced by our disturbance, thus we considered the PSR minimal.

Journal of Wildlife Management↗
USGS1989

Nesting phenology and success of ring-necked ducks in east-central Maine

Selected aspects of the nesting biology of Ring-necked Ducks in east-central Maine were studied during 1983-1985 and compared to previous studies. Nesting chronology, clutch size, and hatching success were similar to results reported from previous studies, but nest success was 32-42% lower. Thirty-eight percent of the nests were successful; % of the eggs in successful nests hatched. Among unsuccessful nests, predation and flooding caused most failures.

Journal of Field Ornithology↗
USGS1989

An improved method to monitor nest attentiveness using radio-telemetry

An improved method of automatically monitoring nest attentiveness was designed and tested using radio-equipped American Woodcock (Scolopax minor). Shielded coaxial cable (RG-58) was extended from a receiver and placed 30 cm above the nest, with a 3.8 cm section of the inner wire exposed. Presence, absence, and activity of birds within 10.1 ? 5.2 m (SD) of the nest were clearly indicated on a Rustrak recorder while extraneous signal interference was minimized.

Journal of Field Ornithology↗
USGS1989

Population ecology and harvest of the American black duck: a review

1. The purpose of our review was to examine available data on population trends and current status of black ducks and trends in natality and survival and to relate these, where possible, to changes in habitat, predation, disease, contaminants, harvest, and hybridization with mallards. 2. The number of black ducks tallied in the winter survey has declined steadily over the past 30 years at an average rate of about 3%/ year. Reliability and precision of the survey are uncertain; it may not provide an adequate index to the continental population of black ducks. Breeding surveys are incomplete and sporadic, but black ducks have decreased in Ontario and increased in the Maritime Provinces and Quebec. 3. Recent declines in numbers of black ducks tallied in the winter survey are not unusual in magnitude or much different from those that have occurred among several other species of waterfowl. 4. At present, black ducks are not especially scarce relative to numbers of several other ducks in eastern North America. 5. There is no solid evidence of major decreases in quality or quantity of breeding habitat for black ducks in recent years; in some areas, habitat has improved. 6. Natural mortality of black ducks has not been well studied, but does not seem unusually high compared to other dabbling ducks. 7. Harvest rates of black ducks are similar to those of sympatric mallards as determined by banding analyses. 8. There is no strong evidence for direct effects of contaminants on black ducks, but some indirect effects through invertebrate food resources have been detected. 9. Age ratios in black ducks show no trend in the past 18 years. 10. The quality and quantity of wintering habitat for black ducks have decreased substantially in some areas. 11. Disease and other natural mortality that affect black ducks do .not occur in unusually high frequency. 12. A decline in harvest of black ducks has occurred; most of the decline has been in the United States, especially since restrictive regulations were implemented in 1983. 13. Recovery rates of black ducks have declined recently in the U.S., but not in Canada. 14. Survival rates of black ducks are 56-63% for adults and 43% for young. These rates of survival are similar to comparable estimates in sympatric mallards. 15. Long hunting seasons may depress survival in some sex-age classes of black ducks, buteffects of small reductions in survival on population trends are unknown. 16. Available evidence does not support the contention that hunting is either the sole or most important cause of the decline in the winter tally of black duck numbers. 17. Surveys and banding of black ducks should be thoroughly reviewed and maintained or improved as warranted. Obtaining or maintaining a reasonable index to numbers of black ducks is the top priority among survey needs. 18. Experimental manipulation of hunting seasons should be considered to elucidate relationships among regulations, harvest, survival, and population trends. 19. Black ducks and mallards are genetically similar; there is as much genetic differentiation within the 2 species as there is between them. 20. Black duck x mallard hybrids are fertile. Hybrids are difficult to detect by plumage and thus published frequencies (0-13%) of hybrids may be low. 21. Hybridization could be a result of concomitant mallard increases and black duck decreases, or changes in black duck-to-mallard ratios could be from hybridization and genetic swamping of black ducks.

Wildlife Society Bulletin↗
USGS1987

Distribution and effects of acidic deposition on wildlife and ecosystems

Acidic deposition occurs over most of the United States and the deposition patterns and theoretical vulnerabilities of aquatic ecosystems to chemical changes can be delineated, but few data exist on concomitant biological effects. Hypothetical direct effects are limited primarily to toxicity of various heavy metals mobilized at reduced pH. Results of studies in Scandinavia suggest that aluminum interferes with avian reproduction near acidified lakes. Some amphibian populations located on acid-vulnerable substrates may be adversely affected by reduced pH in the vernal pools used for egg laying and larval growth. Indirect effects on populations are difficult to detect because few historical data exist for wildlife populations and trophic relationships in vulnerable areas. Current research in the U.S.A. focuses on measuring habitat characteristics, food availability, and avian use of vulnerable wetland habitats. Results of Scandinavian studies suggest that some species of waterfowl may prefer acidified, I fish-free habitats because invertebrates essential for meeting nutritional requirements are more easily obtained in the absence of competition from fish. However, avian species dependent on fish would be absent from these habitats. Alteration of either the vegetative structure or primary productivity of wetlands might indirectly affect avian populations by causing decreased invertebrate productivity and consequent food limitations for birds.

Book chapter↗
USGS1987

Black duck-mallard interactions on breeding areas in Maine

Mallard (Anas platyrhynchos) pairs (2-4) and broods (1-2) have occurred sporadically each year during recent (1977-86) waterfowl investigations in Maine. State-wide brood counts (1956-1986) for 36 wetlands in Maine depict an average increase of 1-3 mallard broods. Broods occurred mostly on man-made impoundments. Numbers of mallards captured during banding (as a percentage of combined mallards, American black ducks [Anas rubripes] and hybrids) have increased from 4.3 to 28.7% in southern Maine, 3.6 to 9.1% in central Maine, and 0.5 to 2.6% in eastern Maine during the last 3 or 4 decades. The percentage of mallards captured in northern Maine in the last decade averaged 11.8%. The occurrence of mallard x black duck hybrids handled during pre-season banding has been variable among decades, but < 2.0% for all the banding sites. Mixed-species pairs, usually a male mallard and a female black duck have been recorded. . Survival of mallard ducklings to fledging (4/brood) approximates that of black ducks, but our sample of broods (N=7) was small. Paired, male, black ducks aggressively drove away intruding mallards and conspecifics. The role of mallard releases and small marsh construction is implicated in the establishment of the 657 mallard pairs estimated as breeding in Maine.

Transactions of the Northeast Section, The Wildlif↗
USGS1983

Survival of female black ducks, Anas rubripes, during the breeding season

The Mayfield method was used to estimate the survival rate of 19 radio-marked, female Black Ducks (Anas rubripes) in southcentral Maine during 1977-80. An overall survival rate of 0.74 was estimated for the 121-day monitoring period that included the pre-laying and laying, incubation, brood rearing, and post-rearing stages. No differences in survival rates were detected among these stages. Two instrumented hens were killed by Red-shouldered Hawks (Buteo lineatus) and a third was killed by an unknown predator. We found no evidence that the attachment of radio transmitters affected hen survival.

Canadian Field-Naturalist↗
USGS1982

Breeding habitat selection and home range of radio-marked black ducks (Anas rubripes) in Maine

Telemetry techniques were used to monitor the movements and habitat use of 13 female and 7 male black ducks ( Anas rubripes ) in an inland breeding region of south central Maine in 1977–1980. Black ducks preferred persistent emergent, broad-leaved deciduous forested, and broad-leaved deciduous scrub–shrub wetlands over unconsolidated organic bottom, needle-leaved evergreen forested, and broad-leaved evergreen scrub–shrub ponds. Birds also made frequent use of small ephemeral pools and streams throughout the breeding period. Nests were located in several habitats ranging from wetland sites to upland areas 1.5 km from the most frequently used pond. Home range size averaged 119 ha for females and 231 ha for males and did not differ by reproductive stage. Three pairs used only a single pond during the incubation period. Home ranges were linear (linearity index = 2.8), averaging 1956 m long for females and 2755 m for males. Wetlands used most by hens during incubation recesses were not always those located closest to the nest. Radio-marked ducks that returned in subsequent breeding seasons demonstrated fidelity to the previously used home range. Pair bonds of marked birds lasted until day 19 or 20 of incubation for initial nesting attempts.

Maine↗
USGS1982

Nest and brood attentiveness in female black ducks

Incubation rhythms and brood attentiveness of radio-marked Black Ducks (Anas rubripes) were studied in southcentral Maine during 1977-1980. Recess duration and frequency differed between three females nesting near wetlands (x = 82 min, 2.3 recesses/day) and two nesting at upland sites(x = 183 min, I. I recesses/day), but incubation constancy was similar for all birds (x = 86.7%). A fourth wetland-nesting female apparently responded to the absence of down and concealing cover at the nest site by taking shorter and fewer recesses (x= 34 min, 1.0 recesses/day) than did other wetland-nesters with typical nests. Wetland-nesters took longer recesses with increasing air temperature and following long incubation sessions. After their ducklings were two weeks old, two brood-rearing females began leaving their broods to forage on nearby wetlands. Duration of rearing recess (x = 56 min) and total recess time (x = 94 min/day) were less during this mid-rearing stage than during the latter part of rearing (x = 265 min, 488 min/day). The two hen-brood bonds terminated at 43 and 48 days. We suggest that small endogenous nutrient reserves and the low density of invertebrate foods, typical of Black Duck breeding habitat, were critical factors affecting the evolution of Black Duck incubation behavior. Bouts of inattention during brood rearing may have also evolved in relation to food requirements; by foraging on wetlands away from their broods, females avoid competing with offspring for common food resources.

Condor↗
USGS1982

Lead shot incidence in sediments and waterfowl gizzards from Merrymeeting Bay, Maine

Lead shot in bottom sediments from Merrymeeting Bay, Maine, averaged 99,932 shot/ha. More shot (P < 0.05) was present in silt sediments than in sand sediments. Number 6 size shot was the most abundant in all 6 river deltas sampled. Ingested lead shot occurred in gizzards of 6 of 10 waterfowl species. Lead shot occurred in 5.9-8.1% of the black ducks (Anas rubripes) sampled during the hunting seasons of 1976-80. A comparison of 3 gizzard examination methods showed that visual examination of gizzard contents and x-ray examination of contents did not differ in accuracy, but fluoroscopic x-ray examination of intact gizzards was not satisfactory for detecting ingested shot. Projected waterfowl mortality and the effectiveness of the steel shot regulation in reducing lead deposition into the environment are discussed.

Wildlife Society Bulletin↗