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At least 289 records · Page 16Linked to original sources
USGS1985

Light attraction in endangered procellariiform birds: Reduction by shielding upward radiation

Autumnal attraction to man-made lighting causes heavy mortality in fledgling Hawaiian seabirds: Newell's Shearwater ( Puffinus auricularis newelli ), Dark-rumped Petrel ( Pterodroma phaeopygia sandwichensis ), and Band-rumped Storm-Petrel ( Oceanodroma castro ). These threatened, endangered, and rare species (respectively) approach and circle lights on their first flight from mountain nesting colonies on the island of Kauai to the sea. We shielded lights of the largest resort to prevent upward radiation on alternate nights during two fledgling seasons. Shielding decreased attraction by nearly 40%. Most attraction occurred 1-4 h after sunset. Full moon dramatically decreased attraction, a phenomenon that has both theoretical and management implications.

The Auk↗
USGS1985

A search for stability gradients in North American breeding bird communities

To search for the existence of stability gradients in North American breeding land bird communities we operationally defined stability (after Jarvinen 1979) as year-to-year persistence in species composition and distribution of species abundances. From the census data for 174 study plots we derived nine indices that estimate the annual variability of species composition, the species abundance distribution, diversity, and breeding density. The resulting matrix of study plot by stability indices was used to estimate the correlation structure of the stability indices. The correlation matrix was, in turn, subjected to a principal components analysis to derive synthetic gradients of variation. We then searched for patterns of variation in these stability gradients associated with either geographic location or habitat type. Three independent principal component axes reproduced most of the variation in the initial data and were interpreted as gradients of variation in species turnover, diversity, and breeding abundance. Thus, the annual stability of community structure apparently responds independently to species and abundance variation. Despite the clarity of the derived gradients, few patterns emerged when the plots were ordinated by either habitat or geographic location. In general, grasslands showed greater annual variation in diversity than forested habitats, and, for some habitats, northern communities were less stable than more southern communities. However, few of these patterns were very strong, and we interpret them cautiously.

The Auk↗
USGS1984

Annual variation in the distribution, abundance, and habitat response of the palila ( Loxioides bailleui )

We studied the distribution, population size, and habitat response of the Palila ( Loxioides bailleui ) during the 1980-1984 nonbreeding seasons to infer factors that limit the population and to develop management strategies. Distribution was fairly constant from year to year. Palila were confined to the subalpine woodland on Mauna Kea on the island of Hawaii, occurred between 2,000 and 2,850 m elevation, and reached highest densities on the southwest slopes. The population showed large annual fluctuations, from 6,400 birds in 1981 to 2,000 in 1984. The width of woodland was the most important variable in determining habitat response. Palila were more common in areas with greater crown cover, taller trees, and a higher proportion of native plants in the understory. Annual variation in Palila density within a habitat reflected variation in levels of their staple food, mamane pods. The main limiting factors of the population appeared to be the availability of good habitat and levels of their staple food. Palila had strongly depressed densities in the Pohakuloa flats area. This low density could not be explained by gross habitat features or food levels. Site tenacity, thermal stress, disturbance, and disease were hypothesized explanations. Our study indicated that the most effective management strategies would be the removal of feral ungulates and certain noxious plants from Palila habitat and the extension of the woodland zone to areas now intensively grazed.

The Auk↗
USGS1987

Release of captive-reared or translocated endangered birds: What do we need to know?

Attempts to evaluate the success of endangered-species reintroduction programs are frustrated by a lack of reliable information on releases of either endangered or nonendangered species. Although many programs have attempted to establish or augment wild populations with captive-reared or wild-caught birds (Williams 1977), there are few published accounts that allow quantitative statements on the success of releases and the role played by animals subjected to different rearing and release protocols (Berger 1978, Kear and Berger 1980). This makes it difficult to assess accurately the status of these species, or to evaluate the influence of various management actions.

The Auk↗
USGS1990

Renesting by American woodcocks ( Scolopax minor ) in Maine

The American Woodcock ( Scolopax minor ) is one of the earliest ground-nesting birds in the northeastern United States. In Maine, nesting begins in early April when temperatures can drop below freezing and significant snowfall can accumulate. Nests are usually in open woods, where eggs are laid on the ground in a shallow depression (Pettingill 1936, Mendall and Aldous 1943, Sheldon 1967). Peak hatching occurs in early May (Dwyer et al. 1982), when temperatures are cool and precipitation is common. Woodcock chicks are dependent on the female for most of their food for at least seven days after hatching (Gregg 1984). During cool, wet weather, chicks require constant brooding by females; prolonged periods of inclement weather may lead to substantial mortality of chicks (Dwyer et al. 1988).

The Auk↗
USGS1990

American woodcock winter distribution and fidelity to wintering areas

We examined winter distribution and fidelity to wintering areas for the American Woodcock ( Scolopax minor ), which exhibits reversed, sexual size dimorphism. Band-recovery data revealed no difference in winter distributions of different age/sex classes for woodcock from the same breeding ares. Similarly, band recoveries from woodcock banded on wintering grounds revealed no difference in fidelity to wintering sites. Males may winter north of a latitude that is optimal for survival based on physiological considerations, but they gain a reproductive advantage if they are among the first to arrive on the breeding grounds. This may explain our results, which indicate males and females have similar distribution patterns during winter.

The Auk↗
USGS1990

Individual variation in behavior and breeding success of Northern Fulmars

In a sample of breeding Northern Fulmars ( Fulmarus glacialis ) observed in 4-5 years, up to 43% of the variability in 13 attributes of breeding behavior was consistent among individuals or pairs. Sample means for most attributes were correlated in a predictable way with annual levels of breeding success. Except for laying dates, there was little evidence that individual differences in these attributes contributed to variation in breeding success. A test of breeding experience as a contributing factor revealed an interaction between individual and annual components of variation. During years when the whole population did relatively poorly, pairs with no previous breeding experience were affected disproportionately. Late-nesting fulmars were more successful than early layers, possibly because delayed breeding ensured that food availability was adequate for successful incubation.

Alaska↗
USGS1990

Notes on longevity and flightlessness in bristle-thighed curlews

Bristle-thighed Curlews ( Numenius tahitiensis ) are among the least-studied shorebirds in the world. They have a highly restricted breeding range in western Alaska and winter exclusively on remote islands in the central and south Pacific (AOU 1983, Kessel 1989). The status of these birds is not known, but they are considered to be rare throughout their range (Johnsgard 1981). We describe two unusual traits of Bristle-thighed Curlews - exceptional longevity and flightlessness during molt-and discuss their significance to the species' migration and nonbreeding ecology.

The Auk↗
USGS1990

[Book review] Return of the Whooping Crane

Fewer than 40 years ago, Life magazine ran an article decrying the plight of Whooping Cranes ( Grus americana ) on their wintering grounds at Aransas National Wildlife Refuge (Aransas) along the Gulf Coast. The small flock of approximately 20 birds that summered at Wood Buffalo National Park (Wood Buffalo) in Canada and wintered on the Texas coast at Aransas comprised the entire wild population of the species-a population that at the time seemed to be drifting inexorably to- ward extinction. Today, the Aransas/Wood Buffalo flock numbers more than 140 birds, there are more than 30 birds in captivity at the Patuxent Wildlife Research Center (Patuxent), and another 20-plus birds at the International Crane Foundation in Baraboo, Wisconsin. There are also a dozen wild birds in an experimental flock (termed the Rocky Mountain flock by Doughty) that winters at Bosque Del Apache National Wildlife Refuge (NWR) in New Mexico and summers in the mountain valleys centered on Grays Lake NWR in Idaho.

The Auk↗
USGS1991

Thirty-eighth supplement to the American Ornithologists' Union Check-list of North American birds

This fourth supplement after the 6th edition (1983) of the AOU "Check-list of North American Birds" consists of changes adopted by the Committee on Classification and Nomenclature between 1 March 1989 and 1 March 1991. The changes fall into eight categories: (1) five species ( Ixobrychus sinensis, Porphyrula flavirostris, Sterna bergii, Streptopelia orientalis , and Ficedula narcissina ) are added to the main list because of new distributional information; (2) six species ( Pterodroma cervicalis, Ortalis wagleri, Lophornis brachylopha, Corvus sinaloae, Cinclocerthia gutturalis , and Loxops caeruleirostris ) are added to the list because of the splitting of species previously in the list; (3) one extinct species ( Dysmorodrepanis munroi ) is added to the list because of re-identification of the unique type; (4) one scientific name ( Speotyto cunicularia ) is changed because of generic splitting; (5) one scientific name ( Phalacrocorax brasilianus ) is changed for nomenclature reasons, accompanied by a change in English name; (6) the spelling of one scientific name ( Neocrex colombianus ) is corrected; (7) to other English names are changed or corrected; and (8) one sequencing change is made. No new distributional information is included except as noted above (i.e. minor changes of distribution of distributional records within North America are not included). The twelve additions bring the number of species recognized as occurring within the Check-list area (main list) to 1957.

The Auk↗
USGS1992

[Book review] Descriptions of thirty-two new species of birds from the Hawaiian Islands: Part I. Non-Passeriformes [and] Part II. Passeriformes

Perhaps the great appeal of paleontological studies is that they inspire visions of past worlds richer and more interesting than our own. Yet, no matter how fascinating, these fossil creatures and their environments manifest a remoteness measured by more than geological time. But what if bones tell the story of a world that ought to still exist? In their long-awaited, twin monographs describing 32 species of subfossil birds from the Hawaiian Islands and commenting on the remains of perhaps as many as 22 other species, the authors more than double in size the recent endemic avifauna for this subtropical, oceanic archipelago.

The Auk↗
USGS1992

Roosting behavior of premigratory Dunlins ( Calidris alpina )

We studied roosting behavior of Dunlins ( Calidris alpina ) during late summer along the coast of the Yukon-Kuskokwim Delta, Alaska, in relation to tidal cycle, time of day, time of season, and occurrence of predators. Within Angyoyaravak Bay, peak populations of 70,000-100,000 Dunlins occur each year. The major diurnal roost sites were adjacent to intertidal feeding areas, provided an unobstructed view of predators, and were close to shallow waters used for bathing. At one site studied intensively, roosting flocks formed at high water consistently during the day but rarely at night. On about 75% of the days, Dunlins also came to the roost at dawn and dusk when the tide was low. The size of the roosting flock, the length of time birds spent at the roost site, and behavior at the roost site were highly variable throughout the season and significantly affected by both tide level and time of day. Roosting behavior changed significantly between early and late August, as Dunlins underwent heavy wing and body molt, and began premigratory fattening. The reaction of Dunlins to potential predators, the formation of roosting flocks in response to light cues, and seasonal changes in social behavior at the roost site suggested that communal roosting behavior may be related not only to the risk of predation but also to behavior during migration.

Alaska↗
USGS1994

Observer differences in the North American Breeding Bird Survey

Because count data collected in many bird surveys are only an index to population size, factors that can influence the counts must be identified and incorporated into analyses. Observer quality is often ignored in analyses of population changes from survey data, but observers differ in methods and capabilities and, hence, tend to count different numbers of birds. We assess the consequences of between-observer differences in counts for estimation of population trends in the North American Breeding Bird Survey. Observer differences in numbers of birds counted were found in 50% of the 369 species we examined. For many species, observers in later years tended to count more birds than observers in earlier years, suggesting an increase in observer quality over time. Analysis of population trends from 1966 through 1991 indicates that failure to include observers as covariables in the analysis results in an overly optimistic view of population trends.

The Auk↗
USGS1994

Charadrius montanus : Montane, grassland, or bare-ground plover?

The Mountain Plover ( Charadrius montanus ) is an aridland member of the Charadriidae. This plover is generally considered an associate of the North American shortgrass prairie, which is dominated by blue grama ( Bouteloua gracilis ) and buffalo grass ( Buchloe dactyloides ; Graul 1975). The species breeds at many locations across the western Great Plains plus at isolated locales in western Colorado, Wyoming and New Mexico (Leachman and Osmundson 1990) and recently in eastern Utah (K.S. Day pers.comm.). Continental populations of the Mountain Plover declined 63% from 1966 to 1991 (Knopf 1994), with the historic and current breeding stronghold being the Pawnee National Grassland in Weld County, Colorado (Graul and Webster 1976). Currently, a second major breeding population of Mountain Plovers is on the Charles M. Russell National Wildlife Refuge, Phillips County, Montana. Unlike when found on the grassland landscape of Weld County, Mountain Plovers in Phillips County selectively nest in prairie dog ( Cynomys spp.) towns (Knowles et al., 1982, Olson and Edge 1985) in vegetative settings that include prickly pear ( Opunitia polyacantha ), fringed sagewort ( Arteminisia frigida ), big sagebrush ( A. tridentata ), western wheatgrass ( Agropyron smithii ), and blue grama, Collectively, Weld and Phillips counties provide nesting habitat for approximately one-half of the continental population of Mountain Plovers,

The Auk↗
USGS1993

Optimal allocation of point-count sampling effort

Both unlimited and fixed-radius point counts only provide indices to population size. Because longer count durations lead to counting a higher proportion of individuals at the point, proper design of these surveys must incorporate both count duration and sampling characteristics of population size. Using information about the relationship between proportion of individuals detected at a point and count duration, we present a method of optimizing a point-count survey given a fixed total time for surveying and travelling between count points. The optimization can be based on several quantities that measure precision, accuracy, or power of tests based on counts, including (1) mean-square error of estimated population change; (2) mean-square error of average count; (3) maximum expected total count; or (4) power of a test for differences in average counts. Optimal solutions depend on a function that relates count duration at a point to the proportion of animals detected. We model this function using exponential and Weibull distributions, and use numerical techniques to conduct the optimization. We provide an example of the procedure in which the function is estimated from data of cumulative number of individual birds seen for different count durations for three species of Hawaiian forest birds. In the example, optimal count duration at a point can differ greatly depending on the quantities that are optimized. Optimization of the mean-square error or of tests based on average counts generally requires longer count durations than does estimation of population change. A clear formulation of the goals of the study is a critical step in the optimization process.

The Auk↗
USGS1994

Sources of variation in loss rates of color bands applied to adult roseate terns ( Sterna dougallii ) in the western North Atlantic

A model-based analysis was done to test several hypotheses concerning the rates of loss of butt-ended color bands placed on adult Roseate Terns ( Sterna dougallii ) in the western North Atlantic. These birds were captured and color banded from 1987-1991 at four colony sites, and recaptured from 1989-1992 as part of a study of the population dynamics of this species. Two types of color bands, Darvic and celluloid, were used, but only one band type was used for each individual bird. Each bird was given three color bands. The estimated probability that a bird with all color bands present during one breeding season still had all color bands during the next breeding season was 0.87. The analysis provided no evidence that colony site, cohort, calendar year of banding, age of color band, or whether or not the bands were heat-sealed closed, were important sources of variation in band-retention probabilities.

The Auk↗
USGS1996

First-time observer effects in the North American Breeding Bird Survey

Currently the operational analysis of Breeding Bird Survey (BBS) data by the National Biological Service accounts for observer differences in estimating the trend for each route, but within-observer differences are not modeled. We tested for the existence of a form of within-observer differences in skill level, namely a change in ability to count birds of a given species after an observer's first year on a given route. An increase in ability could positively bias the trend estimate. Removal of an observer's first year of observation on each route for the period 1966 to 1991 resulted in lower average unweighted trend estimates for 415 of 459 species (90%). These reductions were statistically significant for 213 species (46%). The average reduction in trend was 1.8% change per year (SD = 5.4%). In route-regression analysis, route data are weighted by a measure of precision. Removing first-year observer counts reduced the weighted trend estimate for 275 of 416 species (66%), but differences generally were small.

The Auk↗
USGS1996

Geographic variation in migratory behavior of greater white-fronted geese ( Anser albifrons )

We studied the migration and winter distribution of adult Greater White-fronted Geese ( Anser albifrons frontalis ) radio-marked on the Yukon-Kuskokwim Delta (YKD) and Bristol Bay Lowlands (BBL) of Alaska from 1987 to 1992. The major autumn staging site for geese from both breeding areas was the Klamath Basin on the California/Oregon border. However, temporal use of this area differed markedly between populations. Geese from the BBL arrived at the Klamath Basin nearly 30 days before geese from the YKD and departed before most YKD geese had arrived. Ninety percent of BBL geese used the Klamath Basin in autumn, whereas 30% of YKD geese bypassed the Klamath Basin during autumn and instead flew directly to the Central Valley of California. Nearly all BBL geese migrated directly from the Klamath Basin to wintering areas in Mexico, bypassing the Central Valley. Ninety percent of the BBL geese wintered in Mexico, as opposed to <20% of the YKD geese. Wetlands of the Interior Highlands in the state of Chihuahua, particularly Laguna Babicora, were used by >90% of the radio-marked geese in Mexico. Marshes along the West Coast comprised the other important wintering habitat in Mexico. The Sacramento Valley of California was the predominant wintering area for YKD geese. BBL geese migrated north from Mexico into the San Joaquin Valley or Sacramento-San Joaquin Delta of California by the last week of January. Fifty-five percent of the BBL population used the Klamath Basin in spring, but many birds staged in eastern Oregon and western Idaho. In contrast, geese from the YKD staged almost exclusively in the Klamath Basin during spring before flying to staging areas in Alaska. Breeding allopatry and temporal partitioning on staging and wintering areas likely has contributed to the evolution of previously described phenotypic differences between these populations. These two populations, along with the Tule Greater White-fronted Goose (A. a. gambeli), may constitute a portion of a Rassenkreis, a group of subspecies connected by clines, each ecotype of which has independent conservation needs.

The Auk↗