Geology Reports⌕ Search

Geology topics

D. A. Buhl

Publications and source records attributed to D. A. Buhl.

8 recordsLinked to original sources
USGS2011

Selection of nest-site habitat by interior least terns in relation to sandbar construction

Federally endangered interior least terns ( Sternula antillarum ) nest on bare or sparsely vegetated sandbars on midcontinent river systems. Loss of nesting habitat has been implicated as a cause of population declines, and managing these habitats is a major initiative in population recovery. One such initiative involves construction of mid-channel sandbars on the Missouri River, where natural sandbar habitat has declined in quantity and quality since the late 1990s. We evaluated nest-site habitat selection by least terns on constructed and natural sandbars by comparing vegetation, substrate, and debris variables at nest sites ( n = 798) and random points ( n = 1,113) in bare or sparsely vegetated habitats. Our logistic regression models revealed that a broader suite of habitat features was important in nest-site selection on constructed than on natural sandbars. Odds ratios for habitat variables indicated that avoidance of habitat features was the dominant nest-site selection process on both sandbar types, with nesting terns being attracted to nest-site habitat features (gravel and debris) and avoiding vegetation only on constructed sandbars, and avoiding silt and leaf litter on both sandbar types. Despite the seemingly uniform nature of these habitats, our results suggest that a complex suite of habitat features influences nest-site choice by least terns. However, nest-site selection in this social, colonially nesting species may be influenced by other factors, including spatial arrangement of bare sand habitat, proximity to other least terns, and prior habitat occupancy by piping plovers ( Charadrius melodus ). We found that nest-site selection was sensitive to subtle variation in habitat features, suggesting that rigor in maintaining habitat condition will be necessary in managing sandbars for the benefit of least terns. Further, management strategies that reduce habitat features that are avoided by least terns may be the most beneficial to nesting least terns.

Missouri River↗
USGS2011

Emergent sandbar construction for least terns on the Missouri River: Effects on forage fishes in shallow-water habitats

Emergent sandbars on the Missouri River are actively managed for two listed bird species, piping plovers and interior least terns. As a plunge-diving piscivore, endangered least terns rely on ready access to appropriately sized slender-bodied fish: <52 mm total length for adults and <34 mm total length for young chicks. As part of a multi-agency recovery programme, aimed at enhancing nesting habitat for plovers and terns, the U.S. Army Corps of Engineers mechanically created several emergent sandbars on the Missouri River. However, it was unknown whether sandbar construction is a benefit or a detriment to forage abundance for least terns. Therefore, we studied the shallow-water (<1.5 m) fish community near river and mechanically created emergent sandbars during three nesting seasons (2006–2008). We sampled every 2 weeks each year from late May to July within 15–16 areas to document the relative abundance, species richness and size classes of fish. Fish relative abundance was negatively related to depth. Catches were dominated by schooling species, including emerald shiner, sand shiner, spotfin shiner and bigmouth buffalo. Significant inter-annual differences in relative abundance were observed, with generally increasing trends in intra-seasonal relative abundance of shiners and the smallest size classes of fish (<34 mm). Significant differences in the fish communities between the sandbar types were not detected in this study. Results suggest that mechanical sandbar habitats host comparable fish communities at similar levels of relative abundance. Further analyses are required to evaluate if the levels of fish relative abundance are adequate to support least tern foraging and reproduction.

Nebraska, South Dakota↗
USGS2006

Fat dynamics of arctic-nesting sandpipers during spring in mid-continental North America

We measured fresh body mass, total body fat, and fat-free dry mass (FFDM) of three species of Arctic-nesting calidrid sandpipers (Baird's Sandpiper [ Calidris bairdii ], hereafter “BASA”; Semipalmated Sandpiper [ C. pusilla ], hereafter “SESA”; and White-rumped Sandpiper [ C. fuscicollis ], hereafter “WRSA”) during spring stopovers in the Prairie Pothole Region (PPR) of North Dakota, and evaluated the contribution of stored fat to (1) energy requirements for migration to their Arctic-breeding grounds and (2) nutrient needs for reproduction. All spring migrant WRSA ( n = 124) and BASA ( n = 111), and all but 2 of 99 SESA we collected were ≥2 years old. Male and female BASA migrated through North Dakota concurrently, male SESA averaged earlier than females, and WRSA males preceded females. Fat indices (ratio of fat to FFDM) of male and female SESA and WRSA averaged approximately twice those of male and female BASA. Total body fat of male and female BASA increased with date in spring 1980, but not in 1981; slopes were similar for both sexes each year. Male and female SESA arrived lean in 1980 and 1981, and total body fat increased with date in both years, with similar slopes for all combinations of sex and year. Male and female WRSA arrived lean in 1980–1981 and 1981, respectively, and total body fat increased with date, whereas females arrived with fat reserves already acquired in 1980. Interspecific and sex differences in migration schedules probably contributed to variation in fat storage patterns by affecting maintenance energy costs and food availability. Estimated flight ranges of BASA suggest that few could have met their energy needs for migration to the breeding grounds exclusively from fat stored by the time of departure from North Dakota. Estimated flight ranges of SESA and WRSA, along with fresh body masses of both species when live-trapped on or near their breeding grounds in northern Canada, suggest that major parts of both populations stored adequate fat by departure from temperate mid-continental North America to meet their energy requirements for migration and part of their nutrient needs for reproduction.

The Auk↗
USGS2006

Factors influencing soil invertebrate communities in riparian grasslands of the central platte river floodplain

In the Platte River Valley of central Nebraska, USA, riparian grasslands (also known as wet meadows) have been severely impacted by a reduction in river flows, causing lower ground-water levels and altered seasonal hydroperiods. The potential impacts of these hydrologic changes, as well as the environmental factors that influence wet meadow soil invertebrate communities, are not well understood. An understanding of the ecological processes that influence these invertebrate communities is crucial for maintaining and restoring wet meadows along the Platte River. Our objectives were to describe the soil invertebrate community of wet meadows throughout the growing season and to examine the relative roles of abiotic factors in determining patterns in invertebrate community structure. We conducted the study in 12 wet meadows along the Platte River during 1999 and 2000. We identified 73 invertebrate taxa; 39 were considered soil inhabitants. Total biomass was primarily composed of earthworms, Scarabaeidae, Isopoda, and Elateridae, with earthworms and Scarabaeidae accounting for >82%. Differences in river flow and precipitation patterns influenced some soil invertebrates. Earthworms and Scarabaeidae declined dramatically from 1999 (wet year) to 2000 (dry year). The topographic gradient created by the ridge-swale complex affected several soil invertebrate taxa; Scarabaeidae, Diplopoda, and Lepidoptera biomasses were greatest on drier ridges, while Tipulidae and Isopoda biomasscs were greatest in wetter sloughs. Responses of earthworm taxa to the topographic gradient were variable, but generally, greater biomasses occurred on ridges and mid-elevations. Water-table depth and soil moisture were the most important variables influencing wet meadow soil invertebrates. Because these communities are linked to the hydrologic processes of the Platte River, future alterations of wet meadow hydrology could shift the distribution patterns of many of these invertebrates and possibly eliminate more moisture-tolerant taxa. To maintain wet meadows and their biotic communities, flow management should focus on regaining as much as possible of the former hydrograph through properly timed flows that provide an adequate hydrologic regime for wet meadows. In addition, restoration of wet meadows will depend on restoring the natural topography of wet meadows. ?? 2006, The Society of Wetland Scientists.

Wetlands↗
USGS2000

Effects of water conditions on clutch size, egg volume, and hatchling mass of mallards and gadwalls in the Prairie Pothole Region

We examined the relationship between local water conditions (measured as the percent of total area of basins covered by water) and clutch size, egg volume, and hatchling mass of Mallards ( Anas platyrhynchos ) and Gadwalls ( A. strepera ) on four study sites in the Prairie Pothole Region of North Dakota and Minnesota, 1988–1994. We also examined the relationship between pond density and clutch size of Mallards and Gadwalls, using data collected at another North Dakota site, 1966–1981. For Mallards, we found no relationships to be significant. For Gadwalls, clutch size increased with percent basin area wet and pond density; hatchling mass marginally increased with percent basin area wet. These species differences may reflect, in part, that Mallards acquire lipid reserves used to produce early clutches before they reach the breeding grounds, whereas Gadwalls acquire lipid reserves locally; thus Gadwall clutches are more likely to be influenced by local food resources.

Minnesota, North Dakota↗
USGS1999

Foods and foraging of prairie striped skunks during the avian nesting season

Food habits of prairie skunks are not well understood, yet such knowledge might provide insight into factors influencing nest depredation. We studied food habits of radiocollared adult striped skunks (Mephitis mephitis) during 1976-78 in North Dakota, where skunks are regarded as important predators of ground-nesting birds. Plant foods, primarily grain and sunflower seeds, occurred in a larger percentage of scats in spring (15 Apr 31 May) than summer (1 Jun 15 July, P=0.04), but overall, plant foods were a minor part of skunk diets. Animal foods, primarily birds (including eggs), small rodents, and insects occurred annually in a large percentage of scats of all skunks. These foods were acquired nearly exclusively in grasslands. Percentage of scats containing animal foods was similar, irrespective of sex, season, or year (P>0.45). In spring, vertebrates occurred in a smaller percentage of scats of females than males (P<0.01). Among females, vertebrates also occurred in a smaller percentage of scats in spring than summer (P<0.01). Among all skunks, birds occurred in a smaller percentage of scats in spring than in summer (P<0.01). Both birds (P<0.02) and mammals (P<0.01) occurred in a smaller proportion of scats when wetland conditions were poor. Percentage of scats containing insects, the primary invertebrate food of skunks, did not vary by sex, season, or year (P>0.15). Insects were mostly adult and larval Coleoptera, larval Lepidoptera, and adult and nymph Orthoptera.

Wildlife Society Bulletin↗
USGS1995

Modified transmitter attachment method for adult ducks

The value of radio telemetry for waterfowl research depends on the availability of suitable methods of attaching transmitters. In previous studies, external transmitters attached to adult Mallards (Anas platyrhynchos) with sutures and glue did not stay on birds reliably. In an attempt to improve transmitter retention, a method of attachment was tested in which 4-g transmitters were attached mid-dorsally with sutures and with a stainless steel anchor-shaped wire inserted subcutaneously (anchor transmitters). Field tests indicated that all of 26 female Mallards and 63 of 65 female Gadwalls (Anas strepera) retained their anchor transmitters during 4369 bird-days of monitoring during nesting and brood rearing. Survival rates of females with anchor transmitters compared favorably with those reported from other studies. In this study, females with and without anchor transmitters did not differ with respect to survival rates of their ducklings. The anchor transmitter may be suitable for a variety of field studies on numerous species.

Journal of Field Ornithology↗