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Research about North America

Source-linked reports with geographic coverage including North America.

At least 181 records · Page 10Linked to original sources
USGS2000

Isotope evidence of paleo-El Niño-Southern Oscillation cycles in loess-paleosol record in the central United States

The δ 13 C of soil carbonate in rhizoconcretions collected from a loess-paleosol sequence in the central United States indicates that growing-season C 3 /C 4 plant ratio oscillated by 35% on a 900 ± 200 yr time scale during the late Wisconsinan glaciation. The pattern appears in phase with advance and retreat of the southern margin of the Laurentide ice sheet, suggesting influence by paleo–El Niño–Southern Oscillation cycles. The δ 13 C of soil organic matter indicates that the annual average C 3 /C 4 plant ratio oscillated only by 18%, with a periodicity of 450 ± 100 yr, and closely matched the cyclic pattern of loess-paleosol layers. It suggests a periodic enhancement of the penetration of the Gulf of Mexico air over the region during this time.

Geology↗
USGS2000

Stage boundary recognition in the Eastern Americas realm based on rugose corals

Most Devonian stages contain characteristic coral assemblages but these tend to be geographically and facies limited and may or may not be useful for recognising stage boundaries. Within eastern North America, corals contribute to the recognition of two boundaries: the base of the Lochkovian (Silurian-Devonian boundary) and the base of the Eifelian (Lower-Middle Devonian Series boundary).

CFS Courier Forschungsinstitut Senckenberg↗
USGS1999

The 1992 epizootic of Newcastle disease in double-crested cormorants in North America

In the summer of 1992, morbidity and mortality in juvenile double-crested cormorants (Phalacrocorax auritus; DCC) attributable to Newcastle disease virus (NDV) was observed for the first time in seven northern USA states and one Canadian province, and recurred in three western Canadian provinces. Based on clinical signs and laboratory diagnostic findings, DCC mortality from NDV occurred in 59 of the 63 nesting colonies and two of three non-colony sites investigated. An estimate of in excess of 20,000 DCC died, with mortality rates ranging from < 1 to 37% in Great Lakes colonies to 20 to 92% in Minnesota (USA) and North and South Dakota (USA) colonies. Sick juvenile white pelicans (Pelecanus erythrorhynchos) exhibiting signs similar to sick cormorants, and dead pelicans were observed in Minnesota and North Dakota. Mortality rates in pelican colonies were as high as in the adjacent cormorant colonies, but no cause for the mortality of an estimated 5,000 pelicans was determined. No evidence of NDV was found in other species nesting in proximity to affected cormorants. Although the source of the NDV infection is unknown in cormorants, the simultaneous onset of the epizootics in juvenile birds over a wide geographic area implies that the virus was acquired by adults prior to migration and was carried back to nest sites, exposing susceptible nestlings. The possible transmission of this virus from free-ranging wild birds to domestic poultry is a concern. Based on repeated epizootics in cormorants since 1990, NDV seems to be established in DCC.

Journal of Wildlife Diseases↗
USGS1998

Paleoclimate simulations for North America over the past 21,000 years: Features of the simulated climate and comparisons with paleoenvironmental data

Maps of upper-level and surface winds and of surface temperature and precipitation illustrate the results of a sequence of global paleoclimatic simulations spanning the past 21,000 yr for North America. We review (a) the large-scale features of circulation, temperature, and precipitation that appear in the simulations from the NCAR Community Climate Model Version 1 (CCM 1), (b) the implications of the simulated climate for the past continental-scale distributions of three plant taxa ( Picea spp., Pseudotsuga menziesii , and Artemisia tridentata ), which are broadly representative of the vegetation across the continent, and (c) the potential explanations in terms of atmospheric circulation or surface energy- and water-balance processes for mismatches between the simulations and observations. Most of the broad-scale features of previous paleoclimatic simulations with the NCAR CCM 0 for North America are present in the current simulations. Many of the elements of a conceptual model (based on previous climate simulations) that describes the controls of paleoclimatic variations across North America during the past 21,000 yr are found in simulations reviewed here. These include (1) displacement of the jet stream by the Laurentide Ice Sheet to the south of its present position in both winter and summer, (2) generation of a ‘glacial anticyclone’ over the ice sheet at the LGM, and the consequent induction of large-scale sinking motions induced over eastern North America, (3) changes in the strength of surface atmospheric circulation features through time, including weakening of the Aleutian low in winter, and strengthening of the eastern Pacific and Bermuda high-pressure systems in summer as the ice sheet decreased in size, (4) development of a ‘heat low’ at the surface and a strengthened ridge in the upper-atmosphere over the continent at the time of the maximum summer insolation anomaly, (5) increases in summer temperature earlier in regions remote from the ice sheet (these increases appear earlier in the present (CCM 1) simulations than in the previous (CCM 0) ones, however), and (6) continuation of negative winter temperature anomalies into the middle Holocene. In general, simulated surface conditions that are discordant with paleoenvironmental observations can be attributed to the simulation of particular atmospheric circulation patterns (e.g. those that suppress precipitation or advect warm air into a region), with these mismatches amplified in Beringia and the southeastern United States by surface energy- and water-balance processes.

Quaternary Science Reviews↗
USGS1998

American Black Duck

The American black duck, with its brownish-black plumage and iridescent violet speculum, is one of the wariest of all the large dabbling ducks (Kortright 1942; Fig. 1). The black duck’s distribution is confined to eastern North America but extends into Manitoba. The black duck breeds in a variety of habitat types, from the brackish coastal marshes of North Carolina to the open boreal forests of northern Quebec and Labrador (Bellrose 1976). In acidic bogs, beaver streams, and sluggish riverine and floodplain habitats of the boreal forest, the black duck’s dark plumage (males and females have similar plumage) blends with the dark organic-stained waters of forested wetlands (Fig. 2).

Book chapter↗
USGS1997

New records with examples of potential host colonization events for hypopi (Acari: Hypoderatidae) from birds

New host, geographic records, or both are established for 14 species of hypoderatid deutonymphs from 14 species of birds in North America. Ten of these records are regarded as examples of a potential host colonization event where these hypopi have become established in hosts other than those with which they are normally associated. Herein, potential host colonization events by hypoderatid deutonymphs are regarded as more of an ecologically determined than physiologically specific phenomenon, often specifically related to sharing of nesting sites in the same rookeries by different host taxa. Neottialges ibisicola Young & Pence is placed as a junior synonym of Neottialges plegadicola Fain. The taxonomic status of Hypodectes propus from columbid versus ardeid hosts needs further study.

Journal of Medical Entomology↗
USGS1996

Uranium provinces of North America — Their definition, distribution, and models

Uranium resources in North America are principally in unconformity-related, quartz-pebble conglomerate, sandstone, volcanic, and phosphorite types of uranium deposits. Most are concentrated in separate, well-defined metallogenic provinces. Proterozoic quartz-pebble conglomerate and unconformity-related deposits are, respectively, in the Blind River–Elliot Lake (BRELUP) and the Athabasca Basin (ABUP) Uranium Provinces in Canada. Sandstone uranium deposits are of two principal subtypes, tabular and roll-front. Tabular sandstone uranium deposits are mainly in upper Paleozoic and Mesozoic rocks in the Colorado Plateau Uranium Province (CPUP). Roll-front sandstone uranium deposits are in Tertiary rocks of the Rocky Mountain and Intermontane Basins Uranium Province (RMIBUP), and in a narrow belt of Tertiary rocks that form the Gulf Coastal Uranium Province (GCUP) in south Texas and adjacent Mexico. Volcanic uranium deposits are concentrated in the Basin and Range Uranium Province (BRUP) stretching from the McDermitt caldera at the Oregon-Nevada border through the Marysvale district of Utah and Date Creek Basin in Arizona and south into the Sierra de Peña Blanca District, Chihuahua, Mexico. Uraniferous phosphorite occurs in Tertiary sediments in Florida, Georgia, and North and South Carolina and in the Lower Permian Phosphoria Formation in Idaho and adjacent States, but only in Florida has economic recovery been successful. The Florida Phosphorite Uranium Province (FPUP) has yielded large quantities of uranium as a byproduct of the production of phosphoric acid fertilizer. Economically recoverable quantities of copper, gold, molybdenum, nickel, silver, thorium, and vanadium occur with the uranium deposits in some provinces. Many major epochs of uranium mineralization occurred in North America. In the BRELUP, uranium minerals were concentrated in placers during the Early Proterozoic (2,500–2,250 Ma). In the ABUP, the unconformity-related deposits were most likely formed initially by hot saline formational water related to diagenesis (»1,400 to 1,330 Ma) and later reconcentrated by hydrothermal events at »1,280–»1,000, »575, and »225 Ma. Subsequently in North America, only minor uranium mineralization occurred until after continental collision in Permian time (255 Ma). Three principal epochs of uranium mineralization occurred in the CPUP: (1) » 210–200 Ma, shortly after Late Triassic sedimentation; (2) »155–150 Ma, in Late Jurassic time; and (3) » 135 Ma, after sedimentation of the Upper Jurassic Morrison Formation. The most likely source of the uranium was silicic volcaniclastics for the three epochs derived from a volcanic island arc at the west edge of the North American continent. Uranium mineralization occurred during Eocene, Miocene, and Pliocene times in the RMIBUP, GCUP, and BRUP. Volcanic activity took place near the west edge of the continent during and shortly after sedimentation of the host rocks in these three provinces. Some volcanic centers in the Sierra de Peña Blanca district within the BRUP may have provided uranium-rich ash to host rocks in the GCUP. Most of the uranium provinces in North America appear to have a common theme of close associations to volcanic activity related to the development of the western margin of the North American plate. The south and west margin of the Canadian Shield formed the leading edge of the progress of uranium source development and mineralization from the Proterozoic to the present. The development of favorable hosts and sources of uranium is related to various tectonic elements developed over time. Periods of major uranium mineralization in North America were Early Proterozoic, Middle Proterozoic, Late Triassic–Early Jurassic, Early Cretaceous, Oligocene, and Miocene. Tertiary mineralization was the most pervasive, covering most of Western and Southern North America.

Bulletin↗
USGS1995

Managing North American waterfowl in the face of uncertainty

Informed management of waterfowl (or any animal population) requires management goals and objectives, the ability to implement management actions, periodic information about population and goal-related varlables, and knowledge of effects of management actions on population and goal-related variables. In North America, international treaties mandate a primary objective of protecting migratory bird populations, with a secondary objective of providing hunting opportunity in a manner compatible with such protection. Through the years, annual establishment of hunting regulations and acquisition and man-agement of habitat have been the primary management actions taken by federal agencies. Various information-gathering programs were established and, by the 1960s, had developed into arguably the best monitoring system in the world for continentally distributed animal populations. Retrospective analyses using estimates from this monitoring system have been used to investigate effects of management actions on waterfowl population and harvest dynamics, but key relationships arc still characterized by uncertainty. We recommend actively adaptive management as an approach that can meet short-term harvest objectives, while reducing uncertainty and ensuring sustainable populations over the long-term.

Annual Review of Ecology and Systematics↗
USGS1995

Colonial waterbirds

Colonial waterbirds, that is, seabirds (gulls, terns, cormorants, pelicans) and wading birds (herons, egrets, ibises), have attracted the attention of scientists, conservationists, and the public since the turn of the century when plume hunters nearly drove many species to extinction. The first national wildlife refuge at Pelican Island, Florida, was founded to conserve a large nesting colony of the brown pelican ( Pelecanus occidentalis ). The National Audubon Society also established a game warden system to monitor and protect important waterbird colonies. These efforts helped establish federal laws to protect migratory birds and their nesting habitats in North America. Although the populations of many species rebounded in the early part of the 20th century, major losses and alteration of coastal wetlands still threaten the long-term sustainability of many colonial waterbirds. A national, coordinated monitoring program is needed to monitor population status and trends in colonial waterbirds (Erwin et al. 1993). The Canadian Wildlife Service has recently established a national seabird monitoring program (D. Nettleship, CWS, personal communication). In addition, better coordination and cooperation for monitoring waterbirds are needed on both their breeding grounds in North America and their wintering grounds in Latin America where wetland loss is also a critical problem (Erwin et al. 1993). This article summarizes the status and trends of selected waterbird species in North America, but excludes Alaska, Hawaii, and the Pacific coast, which are described elsewhere.

Book chapter↗
USGS1995

Infectious and parasitic diseases of the gray wolf and their potential effects on wolf populations in North America

Numerous infections and parasitic diseases have been reported for the gray wolf, including more than 10 viral, bacterial, and mycotic disease and more than 70 species of helminths and ectoparasites. However, few studies have documented the role of diseases in population dynamics. Disease can affect wolf populations directly by causing mortality or indirectly by affecting physiological and homeostatic processes, thriftiness, reproduction, behavior, or social structure. In addition, wolves are hosts to diseases that can affect prey species, thus affecting wolf populations indirectly by reducing prey abundance or increasing vulnerability to predation. Diseases such as canine distemper and infectious canine hepatitis are enzootic in wolf populations, whereas rabies occurs in wolves primarily as a result of transmission from other species such as artic and red foxes. Contact between wolves and domestic pets and livestock may affect the composition of diseases in wolves and their effects on wolf populations. Dogs were suspected of introducing lice and canine parovirus to several wolf populations. THe potential for disease to affect wolf populations and other wild and domestic animals should be considered in wolf management plans, particularly in plans for reintroduction of wolves to area within their former range.

Conference Paper↗
USGS1995

Canada geese in North America

Canada geese ( Branta canadensis ) are probably more abundant now than at any time in history. They rank first among wildlife watchers and second among harvests of waterfowl species in North America. Canada geese are also the most widely distributed and phenotypically (visible characteristics of the birds) variable species of bird in North America. Breeding populations now exist in every province and territory of Canada and in 49 of the 50 United States. The size of the 12 recognized subspecies range from 1.4 kg (3-lb) cackling Canada goose ( B.c. minima ) to the 5.0 kg (11-lb) giant Canada goose ( B.c. maxima ; Delacour 1954; Bellrose 1976). Market hunting and poor stewardship led to record low numbers of geese in the early 1900's, but regulated seasons including closures, refuges, and law enforcement led to restoration of most populations. Winter surveys were begun to study population trends and set responsible harvest regulations for these long-lived and diverse birds. Winter surveys begun in 1936-37 probably represent the oldest continuing index of migratory birds in North America.

Book chapter↗
USGS1995

North American ducks

Increased predation and habitat degradation and destruction coupled with drought, especially on breeding grounds, have caused the declines of some duck populations. More than 30 species of fucks breed in North America, in areas as diverse as the Arctic tundra and the subtropics of Florida and Mexico. For many of these species, however, the Prairie Pothole region of the north-central United States and south-central Canada is the most important breeding area, although migratory behavior and the life histories of different species lead them to use many wetland habitats. Numerous sources of information are available on the status of duck populations in North America. The two most comprehensive and reliable sources are the Breeding Population and Habitat Survey, conducted since 1955 and encompassing the Prairie Pothole region, boreal forests, and tundra habitats from South Dakota to Alaska (Caithammer et al. 1993), and the Midwinter Survey, encompassing the United States and portions of Canada and Mexico at regular intervals. Results from these surveys are the basis for this article.

Book chapter↗
USGS1995

Decline of northern pintails

The size of the continental breeding population of northern pintail ( Anas acuta ) has greatly varied since 1955, with numbers in surveyed areas ranging from a high of 9.9 million to a low of 1.8 million in 1991. This variation results primarily from differences in the numbers of breeding pintails in the prairie region of Canada and the United States; these numbers ranged from 8.6 million in 1956 to 0.5 million in 1991; numbers in the northern regions from Alaska to northern Alberta and northern Manitoba varied primarily between 1 and 2 million. Breeding pintails prefer seasonal shallow-water habitats without tall emergent aquatic vegetation (Smith 1968). The proportions and distribution of breeding pintails on the prairies vary annually depending on the amount of annual precipitation and the resulting increase or decrease in the availability of suitable breeding habitat (Smith 1970; Johnson and Grier 1988). Changes in the size of the continental pintail population result from changes in production, survival, or both. Consequently, understanding population changes involves detecting variation in survival and production over time and relating that variation to changes in population size. Once the cause of the decline is determined, appropriate management strategies can be developed to reverse it.

Book chapter↗
USGS1995

Shorebirds: East of the 105th meridian

The North American group of shorebirds includes 48 kinds of sandpipers, plovers, and their allies, many of which live for most of the year in coastal marine habitats; other live principally in nonmarine habitats including grasslands, freshwater wetlands, and even second-growth woodlands. Most North American shorebirds are highly migratory, while others are weakly migratory, and even nonmigratory in some parts of their range. Here we discuss shorebirds east of the 105th meridian (roughly east of the Rocky Mountains). Historically, populations of many North American species were dramatically reduces by excessive gunning (Forbush 1912). Most populations recovered after the passage of the Migratory Bird Treaty Act of 1918, although some species never recovered and others have declined again. High proportions of entire populations of shorebirds migrate by visiting one or a small number of "staging sites", areas where the birds accumulate fat to provide fuel before continuing with their long-distance, nonstop flights to the next site (Morrison and Harrington 1979; Senner and Howe 1984; Harrington et al. 1991). Growing evidence (Schneider and Harrington 1981) indicates that staging areas are unusually productive sites with highly predictable but seasonally ephemeral "blooms" of invertebrates, which shorebirds use for fattening. In some cases, especially for "obligate" coastal species, specific sites are traditionally used; even other species sites may shift between years. Because pf this, conservationists believe some species are at risk through loss of strategic migration site (Myers et al. 1987). Other species are threatened by the less of breeding and wintering habitats (Page et al. 1991; Haig and Plissner 1993; B. Leachman and B. Osmundsom, U.S. Fish and Wildlife Service, unpublished data). The predicted consequences of global warming, such as sea-level change, will also strongly affect the intertidal marine habitats, which many species of shorebirds depend upon. Some of the strongest warming effects will be at high latitudes, including those where many shorebirds migrate to breed, as well as south temperate latitudes, where many of them winter.

Book chapter↗
USGS1995

Ecology and conservation of the Marbled Murrelet in North America: An overview

Over the past decade, the Marbled Murrelet has become a focus of much controversy. It was listed as threatened in Washington, Oregon, and California by the U.S. Fish and Wildlife Service in February 1993. In order to aid the various agencies with management, the Marbled Murrelet Conservation Assessment was formed to bring together scientists, managers, and others to gather all the available data on this small seabird. This volume of research is the culmination of that effort. In this chapter, we integrate the results of the investigations and summaries on the past history, present status, and possible future of the species, based on the data presented in this volume and other published research. We also propose what we consider the most important research needs. Then, based on the findings of this volume, we suggest actions for management to help ensure the survival of the species.

Book chapter↗