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At least 19 recordsLinked to original sources
USGS1996

In memoriam: Robert Earl Stewart, Sr., 1913-1993

Robert Earl Stewart, Sr., our colleague, close friend, and mentor, was born on 16 April 1913 in Kansas City, Missouri. He graduated from high school in Grimes, Iowa, received his B.S. in Biology from the University of Iowa in 1936, and his M.S. in Zoology from the University of Michigan in 1937. His post-graduate work on the life history of the Common Yellow throat was published in the Wilson Bulletin in 1953. Bob joined the AOU in 1938, was made an Elective Member in 1949, and a Fellow in 1974. During World War II, he served with the U.S. Navy Medical Corps in the Pacific Theater.

The Auk↗
USGS1973

DDE: Interference with extra-renal salt excretion in the mallard

The effects of DDE on the function of the salt gland, the main route of sodium chloride excretion in marine birds, were investigated in mature mallards, Anas platyrhynchos, maintained on either fresh water or 1 percent salt water and given 0, 10, 100, or 1000 ppm DDE in the diet (12 birds per level). The rate of sodium chloride excretion by the salt gland following injections of concentrated salt solutions was not reduced (from that of controls) in DDE -treated birds maintained on salt water, but was significantly reduced in DDE -treated birds not previously given salt.

Bulletin of Environmental Contamination and Toxico↗
USGS1971

Elevation-relief ratio, hypsometric integral, and geomorphic area-altitude analysis

Mathematical proof establishes identity of hypsometric integral and elevation-relief ratio, two quantitative topographic descriptors developed independently of one another for entirely different purposes. Operationally, values of both measures are in excellent agreement for arbitrarily bounded topographic samples, as well as for low-order fluvial watersheds. By using a point-sampling technique rather than planimetry, elevation-relief ratio (defined as mean elevation minus minimum elevation divided by relief) is calculated manually in about a third of the time required for the hypsometric integral.

Bulletin of the Geological Society of America↗
USGS2000

Breeding season demography and movements of Eastern Towhees at the Savannah River Site, South Carolina

The Eastern Towhee ( Pipilo erythrophthalmus ) has undergone population declines across much of its range, especially in New England. Despite being a widespread and, at one time, a common species, relatively little is known about its natural history, ecology, or demographics. We conducted baseline research on Eastern Towhees at the Savannah River Site, South Carolina, in 1995 and 1996 to estimate breeding season survival rates, nest success rates, breeding densities, and daily movements. We also were interested in whether towhees had differences in survival and movement rates between young and mature managed pine stands. We found that survival rates during the breeding season of radio-marked towhees did not vary by sex or stand type. Daily nest success rates were very low [0.629 ± 0.088 (SE)] as a result of high predation levels. Abundance estimates adjusted for sampling effort differed between years. In 1995, the abundance estimate was significantly lower in mature stands (7.1 ± 0.47) than in young stands (9.6 ± 0.60) while in 1996, there was no different between mature stands (26.2 ± 5.67) and young stands (16.5 ± 3.39). Average daily movements by radio-marked towhees did not vary by sex or stand type. Movements among adjacent stands were common, and sometimes great distances.

South Carolina↗
USGS2000

Age-specific breeding in Emperor Geese

I studied the frequency with which Emperor Geese ( Chen canagica ) of known age were observed breeding on the Yukon-Kuskokwim Delta, Alaska. No one- or two-year old geese were observed on nests. Three-year old geese bred at a lower rate than four-year old geese. These data suggest that patterns of age-specific breeding in Emperor Geese are similar to other sympatrically nesting, large bodied geese [Greater White-fronted Geese ( Anser albifrons )] but delayed relative to smaller bodied geese [Cackling Canada Geese ( Branta canadensis minima ) and Pacific Black Brant ( B. bernicla nigricans )].

The Wilson Bulletin↗
USGS2000

Habitat and landscape correlates of presence, density, and species richness of birds wintering in forest fragments in Ohio

We investigated the distribution of wintering woodland bird species in 47 very small, isolated, woodland fragments (0.54-6.01 ha) within an agricultural landscape in north-central Ohio. Our objectives were to determine correlations between temporal, habitat, and landscape variables and avian presence, density, and species richness within the smallest woodlots occupied by such species. Our results suggest that even common species are sensitive to variation in habitat, landscape, and season. Woodlot area explained the most variation in presence, density, and species richness. Shrub cover was also an important predictor variable for presence of the smallest resident birds. Shrub cover might function as both a refuge from predators and as a windbreak, reducing thermal costs in a flat, open landscape. Landscape factors related to isolation and connectedness were also correlated with species presence and density. The species composition of the community changed through the winter, as did the density of individual species, suggesting that the winter season may play an important role in determining the distributions of bird populations across woodlots. The models presented here for Ohio birds in this specific landscape may have biological inference for other species in similar landscapes.

Ohio↗
USGS2000

Reproductive ecology of the Maui Parrotbill

The endangered Maui Parrotbill ( Pseudonestor xanthophrys ) is an excavating, insectivorous Hawaiian honeycreeper endemic to the high elevation rain forests of east Maui, Hawaii. From March 1994 to June 1997, we studied various aspects of their breeding ecology. We color-banded 18 individuals, located and monitored 9 active nests, and took behavioral data during 440 hrs of nest observation. Both members of a pair maintained a year-round, all-purpose territory that included nest sites and food resources. Maui Parrotbill were monogamous within and between years; we found no evidence of polyandry, polygyny, or helpers at the nest. Nests were cup-shaped, composed mainly of lichen interlaced with small twigs, and positioned in the outer canopy forks of mature ohia ( Metrosideros polymorpha ) trees. Modal clutch size was one. Females performed most nest construction and all incubation and brooding; males provisioned females and assisted in feeding nestlings after their fourth day. Fledglings depended on parental care for 5–8 months, during which their bill strength increased and foraging skills improved. We calculated the overall nest success rate by the Mayfield Method as 0.42 for the 1995/1996 and 1996/1997 breeding seasons combined. Nest failure and fledgling disappearance coincided with events of high rainfall. Their breeding ecology most closely resembled the Akiapolaau ( Hemignathus munroi ), another excavating, insectivorous Hawaiian honeycreeper found on Hawaii Island. As with the Akiapolaau, the threat of extinction is persistent and results from both the constraints of inherent life history traits and artificial ecological changes. We advocate the protection and expansion of habitable forest areas and an ongoing program to monitor and mitigate the effects of invasive species.

Hawai'i↗
USGS2002

Does Mallard clutch size vary with landscape composition?

We studied Mallards ( Anas platyrhynchos ) nesting in artificial nesting structures in northeastern North Dakota and compared clutch size between landscapes where proportion of cropland was either high (mean = 68.9%, cropland landscapes) or low (mean = 30.2%, grassland landscapes). Mallard clutch size was significantly related to nest initiation date and landscape composition. Mean clutch size, controlled for nest initiation date, was 1.24 ± 0.33 SE eggs smaller on cropland landscapes than on grassland landscapes. Generality of this pattern across space, time, and type of nesting sites is unknown, as is causation. Demographic importance of variation in clutch size may be influenced by covariation with other demographic variables, such as nest success and abundance of breeding pairs, which also are negatively correlated with landscape proportion of cropland. We suggest that researchers examine relationships between clutch size and landscape composition in both structure-nesting and ground-nesting Mallards, in other geographic areas, and in other duck species.

The Wilson Bulletin↗
USGS2002

Helping at a Henslow's Sparrow nest in Wisconsin

We document the first reported observation of helping at the nest of a Henslow's Sparrow ( Ammodramus henslowii ). Video surveillance recorded two unbanded adults (a presumed male and female) and one banded adult male feeding chicks. No intraspecific aggression among the adults was observed.

Wisconsin↗
USGS2002

Re-evaluating Bay-breasted Warbler breeding range: Nine-years presence in Lower Michigan

he breeding range of the Bay-breasted Warbler ( Dendroica castanea ) is thought to include only the northernmost portions of six northeastern and northcentral states in the United States. During a 10-year banding study of Kirtland's Warblers ( Dendroica kirtlandii ) in northern Lower Michigan, we caught 44 Bay-breasted Warblers outside of their reported migration dates during 9 of the 10 years. Two birds captured in 1997 were in breeding condition; one possessed a cloacal protuberance and the other a full brood patch. We also captured two hatching year birds with fleshy rictal flanges in 1997. We suggest that these records indicate a long term presence of Bay-breasted Warblers on breeding grounds considerably farther south than previously recorded.

Michigan↗
USGS2002

Grassland birds orient nests relative to nearby vegetation

We studied orientation of nest sites relative to nearby vegetation for dabbling ducks (Cinnamon Teal, Anas cyanoptera ; Blue-winged Teal, A. discors ; Gadwall, A. strepera ; Mallard, A. platyrhynchos ; and Northern Shoveler, A. clypeata ) and Short-eared Owls ( Asio flammeus ) in ungrazed grassland habitat during 1995–1997 in westcentral Montana. We estimated an index of vegetation height and density in intercardinal directions (NE, SE, SW, NW) immediately around nests. All species oriented nests with the least vegetation to the southeast and the most vegetation to either the southwest or northwest. Furthermore, maximum vegetation around nests shifted from the southwest to the northwest with increasing nest initiation date, apparently as a response of individuals tracking seasonal change in the afternoon solar path. Thus, nests were relatively exposed to solar insolation during cool morning hours but were shaded from intense insolation in the afternoon throughout the breeding season. We suggest that nest microhabitat was selected in part to moderate the thermal environment.

Montana↗
USGS2002

Timing and magnitude of Broad-winged Hawk migration at Montclair Hawk Lookout, New Jersey, and Hawk Mountain Sanctuary, Pennsylvania

The Broad-winged Hawk ( Buteo platypterus ) breeds in eastern and central Canada and the United States, and winters in Central America and northern and central South America. Birders and ornithologists count migrating Broad-winged Hawks at dozens of traditional watch sites throughout the northeastern United States. We modeled counts of migrating Broad-winged Hawks from two raptor migration watch sites: Montclair Hawk Lookout, New Jersey, and Hawk Mountain Sanctuary, Pennsylvania, to determine whether annual abundance and trend estimates from individual sites within the mid-Atlantic states are representative of the region as a whole. We restricted ourselves to counts made between 10:00 and 16:00 EST during September to standardize count effort between sites. We created one model set for annual counts and another model set for daily counts. When modeling daily counts we incorporated weather and identity of individual observers. Akaike’s Information Criteria were used to select the best model from an initial set of competing models. Annual counts declined at both sites during 1979–1998. Broad-winged Hawk migration began, peaked, and ended later at Montclair than at Hawk Mountain, even though Hawk Mountain is 155 km west-southwest of Montclair. Mean annual counts of hawks at Montclair were more than twice those at Hawk Mountain, but were not correlated. Broad-winged Hawks counted at Montclair may not be the same birds as those counted at Hawk Mountain. Rather, the two sites may be monitoring different regional subpopulations. Broad-winged Hawks counted at the two sites may use different migration tactics, with those counted at Hawk Mountain being more likely to slope soar, and those at Montclair more likely to use thermal soaring. A system of multiple watch sites is needed to monitor various breeding populations of this widely dispersed migrant.

New Jersey, Pennsylvania↗
USGS2002

Ring-necked Pheasant parasitism of Lesser Prairie-Chicken nests in Kansas

We report observations of Ring-necked Pheasants ( Phasianus colchicus ) parasitizing Lesser Prairie-Chicken (T ympanuchus pallidicinctus ) nests in native sand sagebrush ( Artemisia filifolia ) rangeland in southwestern Kansas. We found low incidence of interspecific nest parasitism as only 3 of 75 prairie-chicken nests were parasitized. Two of the three parasitized clutches hatched, but no Ring-necked Pheasant chicks were known to have survived.

Kansas↗
USGS2004

Sunrise nest attendance and aggression by least Bell's vireos fail to deter cowbird parasitism

We video-recorded three, natural, brood-parasitism events by Brown-headed Cowbirds ( Molothrus ater ) at nests of Least Bell's Vireos ( Vireo bellii pusillus ). All instances occurred near dawn, during both egg-laying and incubation stages of the nesting cycle. In each case, an adult vireo was on the nest when the female cowbird arrived. Both members of each parasitized pair vigorously attacked the intruding cowbird, but in no encounter did a pair of vireos successfully defend its nest from parasitism. Thus, Least Bell's Vireos in our study were unable to prevent a female cowbird from parasitizing their nests once the cowbird had reached the nest.

The Wilson Bulletin↗