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At least 127 records · Page 7Linked to original sources
USGS1992

Flooding mortality and habitat renewal for least terns and piping plovers

We observed extensive mortality (eggs and chicks) of the endangered interior population of the Least Tern (Sterna antillarum) and threatened Piping Plover (Charadrius melodus) caused by natural flooding during the 1990 breeding season along the Platte River, Nebraska USA. Aerial videography of the Platte River before and after the flood revealed a 78% reduction of perennial vegetation on sandbars. The flood scoured vegetation from sandbars and greatly increased the amount of barren sandbar habitat that nesting Least Terns and Piping Plovers use. A review of river gauging station data indicated that flooding of the 1990 magnitude or greater can be expected to occur about once every nine years. We recommend a review of the annual operating plans of managed rivers to account for the effects of dam discharges on Least Terns and Piping Plovers.

Colonial Waterbirds↗
USGS1990

Feeding activities of black skimmers in Guyana

Discrepancies appear in the literature concerning the influence of time of day and tide on feeding activities of Black Skimmers (Rhynchops niger). Observations from Guyana, South America, suggest that skimmers do feed during the day, but are strongly cued to receding tides.

Colonial Waterbirds↗
USGS1993

Least tern and piping plover nesting at sand pits in Nebraska

Endangered Least Terns (Sterna antillarum) and threatened Piping Plovers (Charadrius melodus) nest at commercial sand and gravel mining operations (sand pits) along the Platte River system in Nebraska. Sandbar habitat has been disappearing since the early 1900's along the Platte River system, but numbers of sand pits have increased. We hypothesized that birds would more fully utilize sand pits where suitable sandbar habitat was limited. We inventoried sand pits and censused terns and plovers on both habitats along the Loup River, part of the North Loup River, and most of the Platte River during 1988-1991. Using aircraft, we also quantified features of suitable sand pits present on the central Platte in 1988 and lower Platte in 1990, and related features to abundance and presence of birds. We found 225 sand pits of which 78 were suitable and 187 were unsuitable for nesting. Along the central Platte, where sandbar habitat is severely degraded, birds nested at 81% of the suitable sand pits (N = 32) at least once during 1988-1991, and most birds (61-94%) nested on sand pits. Along the lower Platte, where both sandbar and sand pit habitat are plentiful, birds nested at 60% of the suitable sand pits (N = 35) at least once during 1988-1991, and most birds (60-86%) nested on sandbars. Numbers of terns and plovers were more weakly correlated with features of sand pits on the central Platte than on the lower Platte. Least Terns and Piping Plovers seem to use more of the suitable sand pit habitat on the central Platte than on the lower Platte. Sand pits probably have influenced the birds' distribution by providing alternative nesting habitat along rivers where suitable sandbars are rare or absent.

Nebraska↗
USGS1993

Chick growth in the California Gull: Relationships with hatching asynchrony and parental age

Chick mass and growth during a six-day period were investigated among California Gulls ( Larus californicus ) in 1979 and 1980. In broods of two, levels of hatching asynchrony between siblings ranging from 0 - 4 days were observed. Hatching asynchrony resulted in initial mass differences between siblings that persisted and accelerated with time. Fledging success was unrelated to hatching asynchrony but was related to large offspring mass and increased with parental age. Parental age was unrelated to hatching asynchrony but heavily influenced the brood's gain in mass. Six days after the second egg hatched, chick mass was highest at those levels of hatching asynchrony where mean age of parent was highest. Mass differences between siblings at day six were related to fledging success only to the extent that rapid growth among siblings of older parents usually resulted in large differences in mass. Implications of results to investigations of Lack's brood reduction hypothesis are discussed.

Wyoming↗
USGS1991

Postfledging survival and recruitment of known-origin roseate terns (Sterna dougallii) at Falkner Island, Connecticut

From 1981-1990, 166 (10.1%) of 1636 Roseate Tern (Sterna dougallii) chicks banded from 1978-1985 at Falkner Island, Connecticut, [USA] and 68 (1.0%) of 6904 chicks banded during the same time period at all other colony sites in Connecticut, New York, and Massachusetts, were recaptured as breeding adults at Falkner Island. An analysis of the recapture data of the natal-site recruits resulted in an estimated average survival-and-return rate of 14.7% for the 3-yr period from fledging to first breeding. Assuming a 10% 'permanent' emigration rate of surviving young to other colony sites, the overall prebreeding survival or maturation rate to age 3 of all fledglings raised at Falkner Island from 1978-1985 was estimated to be about 16%. The 1636 chicks banded at Falkner Island comprised only 19.7% of the total of 8540 chicks banded in the three-state area, but the 166 adults that returned to their natal colony site accounted for 71.4% of the 234 known-age survivors from the 1978-1985 cohorts that had nested at Falkner Island through 1990. The recapture as adults of birds first banded as chicks provides an estimate of the maximum degree to which the breeding population at this site was sustained by natal-site recruitment. The capture of a large number of unbanded birds and birds banded as adults elsewhere indicates, however, that about two-thirds of the recent additions to the Roseate Tern breeding population at Falkner Island were immigrants recruited from other colony sites.

Connecticut↗
USGS1995

Double-crested cormorants along the Upper Mississippi River

The Upper Mississippi River is an important habitat corridor for migratory birds and other wildlife, and it supports an important commercial and sport fishery. A study was initiated by the U.S. Fish and Wildlife Service in 1991 to describe Double-crested cormorant (Phalacrocorax auritus) distribution and abundance on the Upper Mississippi River throughout the year to better understand the possible impacts of cormorants on fish resources and populations of other piscivorous birds. Double-crested Cormorants were common breeders and abundant during migration on the Upper Mississippi River during the 1940s. Numbers of cormorants declined in the 1960s and 1970s along the Upper Mississippi River as they did in other parts of the United States. In 1992, 418 cormorant pairs were estimated to have nested in four colonies on the Upper Mississippi River, and less than 7,000 cormorants were estimated to have migrated along the river during the fall and spring of 1991 and 1992. Recent public concern for fish resources has grown with a perceived growth of the local cormorant population. Migrating cormorants collected on the Upper Mississippi River took Gizzard Shad (Dorosoma cepedianum) primarily, but chicks were fed a wide variety of fish species.

Colonial Waterbirds↗
USGS1995

Population size, trends, and conservation problems of the Double-Crested Cormorant on the Pacific Coast of North America

Population size, trends and conservation problems of the Double-crested Cormorant ( Phalacrocorax auritus ) were collated for the Pacific coast of North America using available data up to 1992. About 54,942 birds currently breed there, including roughly 5,848 (5,622 at 90 coastal colonies and at least 226 at 5 interior colonies) and 49,094 (43,358 at 126 coastal colonies and at least 5,736 at 22 interior colonies) for subspecies P. a. cincinatus in Alaska and P. a. albociliatus , from British Columbia to Sinaloa (Mexico), respectively. In addition, 51 and 22 inactive colonies have been documented in coastal and interior regions, respectively. Major historical declines (in the 1800s and early 1900s) occurred in much of Alaska, California, and Mexico, followed by increases in British Columbia, Washington, Oregon and California from the 1920s to 1980s. Recent declines are occurring in British Columbia, Washington, and Baja California. Trends are affected by apparent movements of nesting birds during El Niño oceanographic conditions and due to habitat loss at interior colonies, as well as recent use of artificial nesting habitats in some areas. Conservation problems have included various forms of human disturbance and persecution, marine pollutants, and high levels of predation owing to introduced and natural predators.

Alaska, California, Oregon, Washington↗
USGS1990

Foraging flights of the white-tailed tropicbird (Phaethon lepturus): Radiotracking and doubly-labelled water

Radiotracking transmitters were fitted to White-tailed Tropicbirds nesting at Culebra, Puerto Rico. Foragers were located by light aircraft out to 89 km SSW of the nesting colony, over a deep-water foraging area south of Vieques Island, Puerto Rico and west of St Croix, U. S. Virgin Islands. Two birds were followed out to 176 km NNW from the colony, over the Puerto Rico Trench, but these did not subsequently return. Foragers carrying radio transmitters performed similarly to those without, in terms of duration of absence from the colony, and mass of food brought for the chick. However, measuremetns of energy consumption by the doubly labelled water method indicated that birds with transmitters consumed significantly more energy than those without.

Colonial Waterbirds↗
USGS1990

Status of the greater flamingo in Haiti

Although flamingos in Haiti can still be found in most areas of their historical range, survey results indicate that numbers have declined drastically over the last 50 years. The coastal mangrove lagoons between Grand Saline and Gonaïves, the inland lakes of Étang Saumâtre and Trou Caïman, and Ile de la Gonâve have been, and remained, the major areas used by flamingos. The species has been extripated from areas with high human population densities (Ile à Vache, Les Cayes, and Cap-Haïtien). No evidence of breeding activity was obtained. The last nesting colony known to occur in Haiti was reported in 1928. Available data suggest that Haiti is mostly utilized by flamingos for feeding and roosting during non-breeding, winter dispersal from Great Inagua, and perhaps Cuba. Flamingo numbers in Haiti are estimated at about 900 (±600) birds. Population trends in Haiti are likely declining due to increasing human disturbance, habitat degradation, and exploitation for food and trade.

Colonial Waterbirds↗
USGS1997

Hematological and plasma biochemical reference ranges of Alaskan seabirds: Their ecological significance and clinical importance

Blood was analyzed from 151 pelagic marine birds to establish reference ranges for hematological and plasma biochemical parameters from healthy, wild populations of Pacific seabirds. Of the 13 species examined, 9 were from the Family Alcidae (N = 122 individuals) and the remainder (N = 29) from the Families Phalacrocoracidae, Laridae, and Procellariidae. Three of 8 hematological parameters (total white blood cell count, lymphocyte count and eosinophil count) differed significantly among species, as did 9 of 13 plasma biochemical parameters (alkaline phosphatase, aspartate aminotransferase, creatine kinase, cholesterol, glucose, lactate dehydrogenase, total bilirubin, total protein and field total protein). There were no differences among species for packed cell volume, buffy coat, cell counts of heterophils, monocytes and basophils, or for concentrations of alanine aminotransferase, triglycerides, uric acid and calcium. Plasma calcium concentration, triglyceride levels and field total protein varied significantly between sexes, with females having higher mean concentrations of all 3 parameters. However, no significant relationships between measures of breeding condition (brood patch size, subcutaneous and mesenteric fat deposits, or ovarian follicle size and ovary weight) and calcium or alkaline phosphatase concentrations in female birds could be identified. Alanine aminotransferase and uric acid were the only analytes which did not differ significantly between species or sexes.

Colonial Waterbirds↗
USGS1997

Female roseate tern fledges a chick following the death of her mate during the incubation period

Despite the death of her mate during the incubation period and a shortage (or lack of availability) of food in nearby waters, a female Roseate Tern (Sterna dougallii) nesting at the Falkner Island Unit of the Stewart B. McKinney National Wildlife Refuge in Connecticut was able to raise a chick to fledging in 1995 without human assistance. The growth and development of this chick was slower than that of other single chicks in the colony; it never weighed more than 90 g and did not fledge until 32 days of age. Despite this exceptional female's ability to rear a chick on her own, this observation supports the idea that bi-parental care is important in Roseate Terns, particularly during years of food shortage.

Colonial Waterbirds↗
USGS1997

Population trends of black terns from the North American Breeding Bird Survey, 1966-1996

Data from the North American Breeding Bird Survey indicate a survey-wide decline in Black Terns (Chlidonias niger) at an average rate of 3.1% annually during 1966-1996. Black Terns in Canada decreased at an average annual rate of 3.5% during this interval, while the United States population showed no significant trends. The long-term declines largely reflect trends prior to 1980, when the continental, Canadian, and United States populations decreased at average annual rates of 7.5%, 5.6%, and 11.9%, respectively. Most population trends were reversed during the 1990s, causing trend estimates over the 1980-1996 interval to become more positive. Associations between patterns of change in Black Terns, Mallards (Anas platyrhynchos), and numbers of ponds in the northern Great Plains suggest some relationships exist between habitat availability and the population trajectories.

Colonial Waterbirds↗
USGS1998

Status of the white-faced ibis: Breeding colony dynamics of the Great Basin population, 1985-1997

The status of the White-faced Ibis (Plegadis chihi) in the Great Basin is of concern because of its small population size and the limited and dynamic nature of its breeding habitat. We analyzed existing annual survey data for the White-faced Ibis breeding in the Great Basin and surrounding area for 1985-1997. Methods varied among colonies and included flight-line counts and fixed-wing aircraft and helicopter surveys. The number of White-faced Ibis breeding pairs in the Great Basin area has nearly tripled since 1985, despite years of severe flooding and drought at major breeding areas. This growth is reflected in both peripheral (i.e., Oregon, California, Idaho) and core (i.e., Nevada and Utah) components of the population. Our data on colony dynamics in Oregon and Nevada illustrate the ability of the highly nomadic White-faced Ibis to compensate for poor conditions at traditional colony sites by moving among colonies and rapidly colonizing newly available wetlands. We suggest that the White-faced Ibis would benefit from a landscape mosaic of well-distributed peripheral wetlands and persistent colony sites. The nomadic nature of the White-faced Ibis and the dynamic nature of their breeding habitat necessitates that wetland management decisions and population monitoring be conducted in a regional context.

Colonial Waterbirds↗
USGS1998

Diets of nestling gull-billed terns in coastal Virginia

We studied the diets of nestling Gull-billed Terns (Sterna nilotica) at colonies in coastal Virginia during the breeding seasons of 1995 and 1996 as part of a long-term study of the species. No previous quantitative assessments had been made of diets of this species anywhere along the Atlantic Coast, and only a few observations had been reported from other coastal areas in the southern United States. During 80 h of observations over the two seasons, 757 feeding observations were made, primarily at two colony sites. We examined how prey type (fish, marine invertebrates, terrestrial prey) and size were influenced by year, tide cycle, season (early and late) and age of the young (small chicks < 7 d old versus large chicks > 7 d). We did not find significant year differences, but all other factors revealed statistically significant results. Older (>7 d) chicks were fed relatively more terrestrial and marine invertebrate prey than were younger chicks. In June (early season), fewer fish and terrestrial prey were fed to chicks than later (July-August). Most prey were less than one bill length in size, with the majority of the smallest prey being marine invertebrates. Tide cycle influenced prey delivered with terrestrial prey becoming relatively more important during high and ebb periods than during low and flood tides when aquatic prey dominated. The major marine invertebrate prey taken was the fiddler crab (Uca spp.). Terrestrial prey consisted mostly of large odonates and orthopterans. Unlike earlier reports from Europe, we found no regurgitated food pellets in any of the colonies in either year. This study confirms that the Gull-billed Tern is an extremely opportunistic feeder and has adapted to a variety of habitats, helping to explain its cosmopolitan distribution.

Virginia↗
USGS1997

Reproduction of black-crowned night-herons related to predation and contaminants in Oregon and Washington, USA

We studied reproductive characteristics of Black-crowned Night-Herons ( Nycticorax nycticorax ) at four colonies in south central Washington and one colony in north central Oregon in 1991. Nest success, adjusted using the Mayfield method, was significantly different between colonies and ranged from 12-84% to hatching and 12-73% to 14 days post-hatching. The mean number of young surviving to 14 days of age in each colony ranged from 0.47-1.94 per nesting female (includes recycling efforts that involve laying more than one clutch). They were marked intercolony differences in clutch size and incidence of recycling. Predation (primarily avian) was a major factor that adversely affected nest success in three colonies and was relatively unimportant in two colonies. Residues of DDE, total polychlorinated biphenyls, 2,3,7,8-tetrachlorodibenzo-p-dioxin, and other compounds in eggs were generally low and apparently had little influence on reproductive success at any of the colonies. Mean eggshell thinning ranged from 7-1 1 % in comparison to a pre-1947 norm for eggs measured in museum collections. Cytochrome P450 enzyme (EROD, PROD, and BROD) induction in livers of pipped embryos by colony ranged from low to average in comparison with other colonies throughout the U.S. Average EROD and BROD activities were highest at Sand Dune Island and were lowest at Potholes Reservoir which was designated the reference colony. In relation to our study of three of the five colonies in the early 1980s, residues of DDE and several related compounds appeared to decline, nest predation rates increased, and nest success decreased at all three colonies.

Oregon, Washington↗
USGS1997

Nesting season food habits of 4 species of herons and egrets at Lake Okeechobee, Florida

Based on the composition of nestling regurgitations collected during 3 breeding seasons, fish were the most important prey group for Great Egrets (Ardea alba: N = 200 nest-day samples; aggregate percent biomass [APB] = 73.4%), Snowy Egrets (Egretta thula: N = 115; APB = 91.4%), and Tricolored Herons (E. tricolor: N = 68; APB = 97.3%). For Little Blue Herons (E. caerulea: N = 57), grass shrimp (Palaemonetes paludosus; APB = 39.7%) ranked higher in overall importance than all fishes combined (APB = 36.5%). Dietary overlap, as measured by Schoener's Similarity Index, was greatest between Snowy Egrets and Tricolored Herons (77%) and lowest between Tricolored Herons and Little Blue Herons (30%). Diet diversity, as measured by Shannon's Index, was highest for Great Egrets (2.04), intermediate for Snowy Egrets (1.71) and Tricolored Herons (1.68), and lowest for Little Blue Herons (1.60). Great Egrets ate a wider variety of fish species and sizes, especially larger fishes, and more crayfish than the other species. Little Blue Herons ate fewer fish and more grass shrimp and insects, and ate smaller forage fishes than Tricolored Herons but similar-sized fish as Snowy Egrets. The coarse-scale trophic composition of Snowy Egret and Tricolored Heron diets did not differ significantly, but Tricolored Herons ate larger forage fishes than Snowy Egrets. Pronounced interannual and intercolony variation in diet composition suggested that Great Egrets and Little Blue Herons switched prey types as hydrologic conditions and habitat availability changed. Conversely, lack of such variation suggested that Snowy Egrets and Tricolored Herons adjusted their foraging tactics to ensure continued encounters with preferred prey despite changing habitat conditions. These results are generally consistent with other published data, help confirm some generalizations about foraging strategies and patterns of niche differentiation among these ecologically similar species, and have implications for managing the Lake Okeechobee ecosystem.

Florida↗
USGS1998

Key areas for wintering North American herons

Nearly all North American heron populations are migratory, but details of where they winter are little known. Locations where North American herons winter were identified using banding recovery data. North American herons winter from Canada through northern South America but especially in eastern North America south of New York, Florida, California, Louisiana, Texas, Mexico and Cuba, these areas accounting for 63% of winter recoveries. We identified regions where recoveries for various species clustered as 'key areas.' These forty-three areas constitute a network of areas that hold sites that likely are important to wintering herons. The relative importance of each area and site within the network must be evaluated by further on the ground inventory. Because of biases inherent in the available data, these hypothesized key areas are indicative rather than exhaustive. As a first cut, this network of areas can serve to inform further inventory activities and can provide an initial basis to begin planning for the year-round conservation of North American heron populations.

Colonial Waterbirds↗