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USGS2003

Response of vegetation and breeding birds to the removal of cattle on the San Pedro River, Arizona (U.S.A.)

In late 1987 cattle were removed from the San Pedro Riparian National Conservation Area ( NCA ) in southeastern Arizona ( U.S.A. ). We monitored vegetation density and abundance of birds during the breeding season during 1986a??1990 in riparian, mesquite grassland, and Chihuahuan desert-scrub communities in the NCA. The density of herbaceous vegetation increased four- to six-fold in riparian and mesquite grassland communities. Little change occurred in herbaceous vegetation in desert scrub, or in the density of shrubs or trees in any of the communities. Of 61 bird species for which sufficient data were collected, mean detections per kilometer increased for 42 species, 26 significantly, and decreased for 19 species, 8 significantly. The number of individuals of all avian species detected on surveys increased each year from 103/kilometer in 1986 to 221/kilometer in 1991, an average annual increase of 23% ( p < 0.001 ). The largest increases occurred in riparian species, open-cup nesters, Neotropical migrants, and insectivores. Species of the Chihuahuan desert-scrub, in which vegetation changed the least, showed the smallest increases. Only a few of the species showed increasing regional trends for the same period, as demonstrated by the North American Breeding Bird Survey; thus, increases on the San Pedro Riparian NCA were likely caused by the change in local conditions, not by regional effects. Our results suggest that removing cattle from riparian areas in the southwestern United States can have profound benefits for breeding birds.

Conservation Biology↗

USGS2015

Stability of detectability over 17 years at a single site and other lizard detection comparisons from Guam

To obtain quantitative information about population dynamics from counts of animals, the per capita detectabilities of each species must remain constant over the course of monitoring. We characterized lizard detection constancy for four species over 17 yr from a single site in northern Guam, a relatively benign situation because detection was relatively easy and we were able to hold constant the site, habitat type, species, season, and sampling method. We monitored two species of diurnal terrestrial skinks ( Carlia ailanpalai [Curious Skink], Emoia caeruleocauda [Pacific Bluetailed Skink]) using glueboards placed on the ground in the shade for 3 h on rainless mornings, yielding 10,286 skink captures. We additionally monitored two species of nocturnal arboreal geckos ( Hemidactylus frenatus [Common House Gecko]; Lepidodactylus lugubris [Mourning Gecko]) on the basis of 15,212 sightings. We compared these count samples to a series of complete censuses we conducted from four or more total removal plots (everything removed to mineral soil) totaling 400 m 2 (about 1% of study site) in each of the years 1995, 1999, and 2012, providing time-stamped quantification of detectability for each species. Unfortunately, the actual population trajectories taken by the four species were masked by unexplained variation in detectability. This observation of debilitating latent variability in lizard detectability under nearly ideal conditions undercuts our trust in population estimation techniques that fail to quantify venue-specific detectability, rely on pooled detection probability estimates, or assume that modulation in predefined environmental covariates suffices for estimating detectability.

Journal of Herpetology↗

USGS2025

Using periodic matrix models to simulate the effectiveness of alternative reintroduction strategies for lizards on a seasonal tropical island

Conservation translocations and reintroductions are widely used to improve conservation outcomes for declining species. Reintroductions are unlikely to be successful if the threats that led to the extirpation of the focal species, such as non-native predators, have not been ameliorated. The non-native brown treesnake ( Boiga irregularis ) was introduced to Guam in the mid-20th century and has devastated the native lizard fauna of this Pacific Island. Native lizard populations persist on small islands near Guam and could act as sources for reintroductions. Recently, trapping methods have been shown to greatly reduce the density of brown treesnakes, raising the possibility that native lizards could be reintroduced where brown treesnake abundance is controlled. Here we developed demographic models for four lizard species present on Guam to assess their validity as a trial for reintroducing species to meet native species recovery goals. These four species vary in their size, activity, and susceptibility to predation by brown treesnakes. We used periodic matrix models to simulate changes in lizard vital rates driven by the wet-dry seasonal cycle found on Guam. We found that the release of 60 individuals of each species was likely to result in successful reintroduction outcomes provided adult survival in the wild is similar to rates estimated based on life history parameters. Demographic models can be used to forecast reintroduction outcomes, including predicting the probability of success and evaluating causes of failure in the event that populations do not establish.

Guam↗

USGS2004

Characterization of water quality in Government Highline Canal at Camp 7 Diversion and Highline Lake, Mesa County, Colorado, July 2000 through September 2003

The U.S. Geological Survey, in cooperation with the Colorado Division of Parks and Recreation, collected and analyzed water-quality data for the Government Highline Canal and Highline Lake from July 2000 through September 2003. Implementation of modernization strategies for the canal, which supplies most of the water to the lake, would decrease the amount of water spilled to Highline Lake from August through October. A reduction in spill water into Highline Lake could adversely affect the recreational uses of the lake. To address this concern and to characterize the water quality in the Government Highline Canal and Highline Lake, the U.S. Geological Survey conducted a study to evaluate limnological conditions prior to implementation of the modernization strategies. This report characterizes the water quality of inflow from the Government Canal and in Highline Lake prior to implementation of modernization strategies in the Government Canal. Flow entering the lake from the Government Canal was characterized using field properties and available chemical, sediment, and bacteria concentrations. Data collected at Highline Lake were used to characterize the seasonal stratification patterns, water-quality chemistry, bacteria populations, and phytoplankton community structure in the lake. Data used for this report were collected at one inflow site to the lake and four sites in Highline Lake. Highline Lake is a mesotrophic/eutrophic lake that has dimictic thermal stratification patterns. Samples collected in the photic zone indicated that there was little physical, chemical, or biological variability at this depth at any of the sampled sites in Highline Lake. Strong thermal and dissolved-oxygen stratification patterns were observed during summer. Dissolved-oxygen concentrations of less than 1 milligram per liter were observed during the summer. Ammonia likely was released from the bottom sediments of Highline Lake. The limiting nutrient in Highline Lake could be nitrogen or phosphorus. In general, the seasonal succession of phytoplankton was similar to that of other lakes in the temperate zone. Several types of algae associated with taste and odor issues were identified in samples, but critical concentrations were not exceeded for any listed algal group with the exception of the diatom genus Cyclotella in one sample. Bacteria concentrations were determined at the public swim beach at Highline Lake. E. coli samples were collected periodically by the USGS and weekly by the Colorado Division of Parks and Recreation. During the study period, no reported E. coli concentration exceeded the standard for natural swimming areas. Inflow water quality was characterized by samples collected at the Camp 7 check structure on the Government Canal. Inflow water temperatures reflected the seasonal patterns of the source water in the Colorado River. The water was well oxygenated. Nitrogen and phosphorus concentrations were low, and concentrations did not differ substantially from year to year or seasonally within a year. All samples had reportable numbers of fecal streptococcus. The maximum reported concentration of E. coli was reported at 77 colonies per 100 milliliters of sample. Suspended-sediment concentrations were relatively low.

Scientific Investigations Report↗

USGS2021

Mismatch-induced growth reductions in a clade of Arctic-breeding shorebirds are rarely mitigated by increasing temperatures

In seasonal environments subject to climate change, organisms typically show phenological changes. As these changes are usually stronger in organisms at lower trophic levels than those at higher trophic levels, mismatches between consumers and their prey may occur during the consumers’ reproduction period. While in some species a trophic mismatch induces reductions in offspring growth, this is not always the case. This variation may be caused by the relative strength of the mismatch, or by mitigating factors like increased temperature-reducing energetic costs. We investigated the response of chick growth rate to arthropod abundance and temperature for six populations of ecologically similar shorebirds breeding in the Arctic and sub-Arctic (four subspecies of Red Knot Calidris canutus , Great Knot C . tenuirostris and Surfbird C . virgata ). In general, chicks experienced growth benefits (measured as a condition index) when hatching before the seasonal peak in arthropod abundance, and growth reductions when hatching after the peak. The moment in the season at which growth reductions occurred varied between populations, likely depending on whether food was limiting growth before or after the peak. Higher temperatures led to faster growth on average, but could only compensate for increasing trophic mismatch for the population experiencing the coldest conditions. We did not find changes in the timing of peaks in arthropod availability across the study years, possibly because our series of observations was relatively short; timing of hatching displayed no change over the years either. Our results suggest that a trend in trophic mismatches may not yet be evident; however, we show Arctic-breeding shorebirds to be vulnerable to this phenomenon and vulnerability to depend on seasonal prey dynamics.

Global Change Biology↗

USGS2014

Mesohabitats, fish assemblage composition, and mesohabitat use of the Rio Grande silvery minnow over a range of seasonal flow regimes in the Rio Grande/Rio Bravo del Norte, in and near Big Bend National Park, Texas, 2010-11

In 2010–11, the U.S. Geological Survey (USGS), in cooperation with the U.S. Fish and Wildlife Service, evaluated the physical characteristics and fish assemblage composition of mapped river mesohabitats at four sites on the Rio Grande/Rio Bravo del Norte (hereinafter Rio Grande) in and near Big Bend National Park, Texas. The four sites used for the river habitat study were colocated with sites where the U.S. Fish and Wildlife Service has implemented an experimental reintroduction of the Rio Grande silvery minnow (Hybognathus amarus), a federally listed endangered species, into part of the historical range of this species. The four sites from upstream to downstream are USGS station 08374340 Rio Grande at Contrabando Canyon near Lajitas, Tex. (hereinafter the Contrabando site), USGS station 290956103363600 Rio Grande at Santa Elena Canyon, Big Bend National Park, Tex. (hereinafter the Santa Elena site), USGS station 291046102573900 Rio Grande near Ranger Station at Rio Grande Village, Tex. (hereinafter the Rio Grande Village site), and USGS station 292354102491100 Rio Grande above Stillwell Crossing near Big Bend National Park, Tex. (hereinafter the Stillwell Crossing site). In-channel river habitat was mapped at the mesohabitat scale over a range of seasonal streamflows. A late summer (August–September 2010) high-flow regime, an early spring (April–May 2010) intermediate flow regime, and a late spring (May 2011) low-flow regime were the seasonal flows used in the study. River habitat was mapped in the field by using a geographic information system and a Global Positioning System unit to characterize the sites at the mesohabitat scale. Physical characteristics of a subset of mesohabitats in a reach of the Rio Grande at each site were measured during each flow regime and included depth, velocity, type and size of the substrate, and percent embeddedness. Selected water-quality properties (dissolved oxygen, pH, specific conductance, and temperature) of a subset of mesohabitats were also measured. The fish assemblage composition at the four sites was determined during the three flow regimes, and fish were collected by seining in each mesohabitat where physical characteristic data were measured, except during some periods of high flow when electrofishing was done to supplement seining. The total number and number of types of mesohabitats were larger during low flows compared to intermediate flows, and larger during intermediate flows compared to high flows. Decreases in streamflow typically led to increases in channel complexity in terms of the number of different types and total number of mesohabitats present. The total wetted area increased and the number of mesohabitat types generally decreased as streamflow increased. At all four sites, the smallest depths and velocities were generally measured during low flow and the largest depths and velocities at high flow. Specific conductance was relatively consistent between the Contrabando and Santa Elena sites, the two most upstream sites. Specific conductance decreased appreciably between the Santa Elena site and the Rio Grande Village, and decreased slightly between the Rio Grande Village site and the Stillwell Crossing site. Specific-conductance values within and among mesohabitat types at a given site were relatively consistent. The pH values measured within and among mesohabitat types also were relatively consistent at all four sites. Median dissolved oxygen concentrations were relatively consistent between the Contrabando and Santa Elena sites (8.34 and 8.54 milligrams per liter [mg/L], respectively) but decreased along the stretch of river between the Santa Elena and Rio Grande Village sites to 7.31 mg/L, possibly because of small dissolved oxygen concentrations associated with contributions from springs between the Santa Elena and Rio Grande Village sites. Dissolved oxygen concentrations increased substantially between the Rio Grande Village and Stillwell Crossing sites to 10.06 mg/L. Mesohabitat water temperatures were generally highest in mesohabitats commonly associated with shallow water depths and low velocities (forewaters, backwaters, and embayments). Of the 21 species of fish collected during the three flow regimes, red shiner ( Cyprinella lutrensis ) was the most abundant species overall, accounting for about 35 percent of all fish collected. Another minnow, the endemic Tamaulipas shiner ( Notropis braytoni ), was second in overall abundance. A nonnative species, the common carp ( Cyprinus carpio ), was the third most abundant species overall. No statistically significant differences in fish-species richness were found among the different mesohabitat types. Median fish-species richness and maximum fish-species richness values were larger, and fish-species richness was more variable in runs, pools, forewaters, and backwaters during low flow compared to the fish-species richness values calculated for intermediate and high flows. Fish density in backwater mesohabitats was significantly different from fish densities in run mesohabitats, but fish densities were not significantly different among the other mesohabitat types. Of the 39 Rio Grande silvery minnow individuals collected at the four study sites, 21 (more than half) were collected at the Santa Elena site, 12 at the Contrabando site, and 3 each at the Rio Grande Village and Stillwell Crossing sites. Rio Grande silvery minnow fish-species densities followed the same order as abundance of this species at the sites; fish-species densities ranged from 0.95 fish per 100 square meters (m 2 ) at the Santa Elena site to 0.11–0.47 fish per 100 m 2 at the other three sites. The Rio Grande silvery minnow was most common in pools and runs during low- and intermediate-flow regimes. This species was less commonly collected in backwaters, embayments, and rapids, and none were collected in forewaters or submerged channel bars. The Tamaulipas shiner has similar life-history characteristics compared to the Rio Grande silvery minnow, including similar feeding habits and habitat use. Tamaulipas shiner was most common in backwater, run, and riffle mesohabitats (in decreasing order) during low and intermediate flow and was less common in submerged channel bar, pool, forewater, rapid, and embayment mesohabitats (in decreasing order) during the same flows. The overall relative percent density (composite of all three flow regimes) of Rio Grande silvery minnow was largest in rapid and pool mesohabitats and for Tamaulipas shiner was largest in backwater mesohabitats. There were no statistically significant differences between the stream velocities associated with seine hauls of the Rio Grande silvery minnow and Tamaulipas shiner. Stream velocities associated with the seine hauls that included Rio Grande silvery minnow indicate that this species is predominantly found in low-velocity mesohabitats. Velocities associated with seine hauls that included the Tamaulipas shiner represented a much broader overall range of velocities than those associated with Rio Grande silvery minnow collections. No statistically significant differences were found between the depths for seine hauls that included Rio Grande silvery minnow or Tamaulipas shiner. The Rio Grande silvery minnow was more commonly collected in seine hauls from mesohabitats dominated by cobble substrates and less frequently collected in mesohabitats with substrates dominated by fine-sized silt and clay particles, gravels, and sands, in that order. In contrast, the Tamaulipas shiner was broadly distributed among mesohabitats characterized as having gravel, cobble, and silt and clay.

Texas↗

USGS2017

Late Quaternary environmental dynamics in the Atacama Desert reconstructed from rodent midden pollen records

In the past two decades, much has been learned about the late Quaternary climate history of the Atacama Desert with some details still unclear about the seasonality, timing and extent of wet and dry phases. Modern climate studies reveal that, far from exhibiting a unique pattern, seasonal precipitation originates from many sources and mechanisms. For the last 16 ka, we attempt to sort out these complexities in pollen records from four fossil rodent midden series spanning 22°–25°S in northern Chile. Widespread wet conditions prevailed during the late Pleistocene and early Holocene, particularly between 13 and 9 ka, evidenced by <400 m lowering of pollen zones (plant communities) compared to today. Regional differences in the timing and magnitude of this displacement may be related to the prevailing source (tropical/extra‐tropical) or mode (NNW/SE) of tropical precipitation through time. Wet conditions persisted well into the early Holocene, lasting ∼1–1.5 ka longer than previously suggested. The pollen record suggests extreme drying ∼8 ka, possibly associated with a northward shift of the Inter Tropical Convergence Zone, tracking minimum insolation values at subtropical latitudes during the austral summer. The establishment of conditions similar to today happened ∼4 ka.

Journal of Quaternary Science↗

USGS2007

Year-class formation of upper St. Lawrence River northern pike

Variables associated with year-class formation in upper St. Lawrence River northern pike Esox lucius were examined to explore population trends. A partial least-squares (PLS) regression model (PLS 1) was used to relate a year-class strength index (YCSI; 1974-1997) to explanatory variables associated with spawning and nursery areas (seasonal water level and temperature and their variability, number of ice days, and last day of ice presence). A second model (PLS 2) incorporated four additional ecological variables: potential predators (abundance of double-crested cormorants Phalacrocorax auritus and yellow perch Perca flavescens), female northern pike biomass (as a measure of stock-recruitment effects), and total phosphorus (productivity). Trends in adult northern pike catch revealed a decline (1981-2005), and year-class strength was positively related to catch per unit effort (CPUE; R2 = 0.58). The YCSI exceeded the 23-year mean in only 2 of the last 10 years. Cyclic patterns in the YCSI time series (along with strong year-classes every 4-6 years) were apparent, as was a dampening effect of amplitude beginning around 1990. The PLS 1 model explained over 50% of variation in both explanatory variables and the dependent variable, YCSI first-order moving-average residuals. Variables retained (N = 10; Wold's statistic ??? 0.8) included negative YCSI associations with high summer water levels, high variability in spring and fall water levels, and variability in fall water temperature. The YCSI exhibited positive associations with high spring, summer, and fall water temperature, variability in spring temperature, and high winter and spring water level. The PLS 2 model led to positive YCSI associations with phosphorus and yellow perch CPUE and a negative correlation with double-crested cormorant abundance. Environmental variables (water level and temperature) are hypothesized to regulate northern pike YCSI cycles, and dampening in YCSI magnitude may be related to a combination of factors, including wetland habitat changes, reduced nutrient loading, and increased predation by double-crested cormorants. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗

USGS1971

Geochemical, aeromagnetic, and generalized geologic maps showing distribution and abundance of mercury and arsenic, Golconda and Iron Point quadrangles, Humboldt County, Nevada

Detailed geologic and geochemical studies of the four 7 1/2-minute wuadrangles that make up the Edna Mountain 15-minute quadrangle in Humboldt County, Nevada, were begun druring the 1969 summer field season. The objectives of the project are to map the geology of this structurally complex area at 1:24,000 scale and to determine the regional distribution and abundance of metals in rocks of the area and the factors that control the distribution and abundance of those metals. Tungsten-bearing hot-spring tufa, metalliferous black shale in Ordovician rocks, base-metal and barite deposits in Paleozoic sedimentary rocks, and copper-molybdenum in granodiorite plutons of Creataceous age occur in the Edna Mountain dare. None of these deposits have been of much economic significance, although tungsten was mined from the hot-spring deposits during World War II.

Nevada↗

USGS1971

Geochemical, aeromagnetic, and generalized geologic maps showing distribution and abundance of antimony and tungsten, Golconda and Iron Point quadrangles, Humboldt County, Nevada

Miscellaneous Field Studies Map↗

USGS1971

Geochemical, aeromagnetic, and generalized geologic maps showing distribution and abundance of gold and copper, Golconda and Iron Point quadrangles, Humboldt County, Nevada

Nevada↗

USGS1971

Geochemical, aeromagnetic, and generalized geologic maps showing distribution and abundance of lead and silver, Golconda and Iron Point quadrangles, Humboldt County, Nevada

Detailed geologic and geochemical studies of the four 7 1/2-minute quadrangles that make up the Edna Mountain 15-minute quadrangle in Humboldt County, Nevada, were begun during the 1969 summer field season. The objectives of the project are to map the geology of this struct urally complex area at 1:24·,000 scale and to determine the regional distribution and abundance of metals in rocks of the are\3. and the factors that control the distribution and abundance of those metals. Tungstenbearing hot-spring tufa, metalliferous black shale in Ordovician rocks, base-metal and barite deposits in Paleozoic sedimentary rocks, and copper-molybdenum in granodiorite plutons of Cretaceous age occur in the Edna Mountain area. None of these deposits have been of much economic significance, although tungsten was mined from the hot-spring deposits during World War II. The numerous occurrences of mineralized ground, however, along with the broad spectrum of types of mineralization, intensity of alteration, structural complexity, and abundance of intermediate to silicic igneous intrusive rocks suggest that concealed or heretofore unrecognized mineral deposits may exist in the area. Integrated geologic, geochemical, and geophysical studies on a district- wide scale might improve our un~erstanding of the factors that control the distribution, methods of emplacement, and spatial and genetic relationships (if any) of these different types of deposits. We hope that broad target areas or guidelines for mineral exploration in th.is area may be identified. This series of maps shows the distribu t ion and abundance of mercury, arsenic, antimony, tungsten, gold, copper, l ead, and s ilver related to a geologic and aeromagnetic base in the Golconda and Iron Point 7 1/2-minute quadrangles. All samples are rock samples; most are f rom shear or f ault zones, fractures, jasperoid, breccia reefs, and altered rocks . All the samples were prepared and analyzed in truck-mounted laboratories at Wi nnemucca, Nevada. Arsenic , tungs t en, copper, lead, and si lver were determined by semiquantitative spectrogr aph i c methods by D. F. Siems and E. F. Cooley . Mercury and gold were determined by atomi c absorption methods and antimony was determined by a colorimetric method by R. M. O'Leary, M. S. Erickson, and others.

Nevada↗

USGS2006

Use of sediment rating curves and optical backscatter data to characterize sediment transport in the Upper Yuba River watershed, California, 2001-03

Sediment transport in the upper Yuba River watershed, California, was evaluated from October 2001 through September 2003. This report presents results of a three-year study by the U.S. Geological Survey, in cooperation with the California Ecosystem Restoration Program of the California Bay-Delta Authority and the California Resources Agency. Streamflow and suspended-sediment concentration (SSC) samples were collected at four gaging stations; however, this report focuses on sediment transport at the Middle Yuba River (11410000) and the South Yuba River (11417500) gaging stations. Seasonal suspended-sediment rating curves were developed using a group-average method and non-linear least-squares regression. Bed-load transport relations were used to develop bed-load rating curves, and bed-load measurements were collected to assess the accuracy of these curves. Annual suspended-sediment loads estimated using seasonal SSC rating curves were compared with previously published annual loads estimated using the Graphical Constituent Loading Analysis System (GCLAS). The percent difference ranged from -85 percent to +54 percent and averaged -7.5 percent. During water year 2003 optical backscatter sensors (OBS) were installed to assess event-based suspended-sediment transport. Event-based suspended-sediment loads calculated using seasonal SSC rating curves were compared with loads calculated using calibrated OBS output. The percent difference ranged from +50 percent to -369 percent and averaged -79 percent. The estimated average annual sediment yield at the Middle Yuba River (11410000) gage (5 tons/mi2) was significantly lower than that estimated at the South Yuba River (11417500) gage (14 tons/mi2). In both rivers, bed load represented 1 percent or less of the total annual load throughout the project period. Suspended sediment at the Middle Yuba River (11410000) and South Yuba River (11417500) gages was typically greater than 85 percent silt and clay during water year 2003, and sand concentrations at the South Yuba River (11417500) gage were typically higher than those at the Middle Yuba River (11410000) gage for a given streamflow throughout the three year project period. Factors contributing to differences in sediment loads and grain-size distributions at the Middle Yuba River (11410000) and South Yuba River (11417500) gages include contributing drainage area, flow diversions, and deposition of bed-material-sized sediment in reservoirs upstream of the Middle Yuba River (11410000) gage. Owing to its larger drainage area, higher flows, and absence of man-made structures that restrict sediment movement in the lower basin, the South Yuba River transports a greater and coarser sediment load.

Scientific Investigations Report↗

USGS1986

Harvest, survival, growth, and movement of five strains of hatchery-reared rainbow trout in Virginia streams

Catchable-size (minimum length 17.8 cm) rainbow trout ( Salmo gairdneri ) of five genetically distinct strains were harvested by anglers at significantly different rates when the fish were stocked into four put-and-take trout streams in southwestern Virginia. Fish from Standard Winter (SW) and Ennis (EN) strains were caught easily; 85.7 and 93.2% of their respective total harvests occurred during the first 2 d of the fishing season. Sand Creek (SC), Fish Lake (FL), and McConaughy (MC) strains were harvested more uniformly over the first 3 weeks of fishing; 64.6, 58.4, and 43.4% of their respective total harvests occurred during the first 2 d. The average total harvests of SC (47.7%) and SW (46.7%) strains were similar and ranked highest among the five strains; however, no strain showed statistical superiority in all four streams. Harvest of the MC strain was consistently and significantly lower than the other four strains within each stream and averaged 25.6%. Average harvests of FL (42.8%) and EN (39.5%) strains were intermediate. Significant environmental (stream) influences and genotype-environment interactions were evident. No significant differences in tendency to move downstream were found. Fish of the EN, SW, and SC strains were significantly more vulnerable to fishing with bait (versus artificial lures) than fish from FL and MC strains. Differences in natural mortality rate, growth, and downstream movement among strains in a fifth, unfished, stream were not significant. Condition factor ( K ) decreased significantly for all five strains in an unfished stream. The MC strain appeared to be poorly suited for put-and-take streams, while SW and SC strains performed about equally well and are worthy of further evaluation in stocked stream environments. Managers should select strains (other than SW or SC) for future evaluation in put-and-take streams based on hatchery performance, but should give consideration to potential masking or damping effects of natural environments.

North American Journal of Fisheries Management↗

USGS2006

Effects of floods on fish assemblages in an intermittent prairie stream

1. Floods are major disturbances to stream ecosystems that can kill or displace organisms and modify habitats. Many studies have reported changes in fish assemblages after a single flood, but few studies have evaluated the importance of timing and intensity of floods on long-term fish assemblage dynamics. 2. We used a 10-year dataset to evaluate the effects of floods on fishes in Kings Creek, an intermittent prairie stream in north-eastern, Kansas, U.S.A. Samples were collected seasonally at two perennial headwater sites (1995-2005) and one perennial downstream flowing site (1997-2005) allowing us to evaluate the effects of floods at different locations within a watershed. In addition, four surveys during 2003 and 2004 sampled 3-5 km of stream between the long-term study sites to evaluate the use of intermittent reaches of this stream. 3. Because of higher discharge and bed scouring at the downstream site, we predicted that the fish assemblage would have lowered species richness and abundance following floods. In contrast, we expected increased species richness and abundance at headwater sites because floods increase stream connectivity and create the potential for colonisation from downstream reaches. 4. Akaike Information Criteria (AIC) was used to select among candidate regression models that predicted species richness and abundance based on Julian date, time since floods, season and physical habitat at each site. At the downstream site, AIC weightings suggested Julian date was the best predictor of fish assemblage structure, but no model explained >16% of the variation in species richness or community structure. Variation explained by Julian date was primarily attributed to a long-term pattern of declining abundance of common species. At the headwater sites, there was not a single candidate model selected to predict total species abundance and assemblage structure. AIC weightings suggested variation in assemblage structure was associated with either Julian date or local habitat characteristics. 5. Fishes rapidly colonised isolated or dry habitats following floods. This was evidenced by the occurrence of fishes in intermittent reaches and the positive association between maximum daily discharge and colonisation events at both headwater sites. 6. Our study suggests floods allow dispersal into intermittent habitats with little or no downstream displacement of fishes. Movement of fishes among habitats during flooding highlights the importance of maintaining connectivity of stream networks of low to medium order prairie streams. ?? 2006 The Authors.

Freshwater Biology↗

USGS2020

Evaluation of survey methods for colonial waterbirds at Chase Lake National Wildlife Refuge, North Dakota

Estimating the number of breeding pairs in a mixed-species waterbird colony is difficult because colonial waterbirds are vulnerable to human intrusion and their colonies are often in remote areas with limited access. We investigated methods to estimate the number of nests of waterbirds at a large, mixed-species colony at Chase Lake National Wildlife Refuge in south-central North Dakota. The primary goals of this study were to evaluate survey methods for shrub- and ground-nesting colonial waterbirds at Chase Lake National Wildlife Refuge and to develop protocols for estimating abundance of the different species. The specific objectives were (1) to assess visible-nest counts for ciconiiform species from the perimeter of nesting areas (hereafter, perimeter counts) and observational surveys from fixed points outside the colony to count flights of adult ciconiiforms in and out of the colony (hereafter, flightline surveys) as alternatives to within-colony counts of ciconiiform nests, and (2) to assess semiautomated, pixel-based image-analysis techniques to estimate abundance of American White Pelicans ( Pelecanus erythrorhynchos ) as an alternative to traditional manual counts from aerial photographs. For shrub-nesting ciconiiform species, observers counted 2,259 and 1,759 active ciconiiform nests in 2012 and 2013, respectively, during within-colony counts of ciconiiform nests. Results from within-colony counts of ciconiiform nests indicated a positive relation between the number of nests and the area of the shrub subcolony for the three most common ciconiiform species and all ciconiiform species combined. The perimeter nest counts of ciconiiform nests at Chase Lake represented only 18.8 percent of the total active ciconiiform nests counted in 11 subcolonies in 2012, which was well below the recommended target of 50 percent. Although we found a positive relationship between the number of nests counted during perimeter counts and the number of nests counted during within-colony counts for the three most common ciconiiform species and all ciconiiform species combined, perimeter counts at Chase Lake were hampered by disturbance to nesting birds. Thus, we discontinued the perimeter counts before they were completed. We did not develop predictive models from these perimeter counts in 2012 because these models could be misleading due to inconsistent application of the survey methods, which likely would have provided inaccurate perimeter counts. The extent of this issue is unknown. Flightline surveys at Chase Lake documented patterns of ciconiiform activity that were unknown for this region. For the common ciconiiform species, the number of flights to and from the South Island at Chase Lake were greatest in the morning (7:00−12:00 central daylight time [CDT]) and least in the afternoon (12:00−17:00), and least early in the breeding season (May 29–June 20, 2013) and greatest later in the breeding season (June 24–August 1, 2013). Flightline surveys are an index but lacked comparability with within-colony nest counts because the two methods provide measures of different things (that is, adult activity away from the colony as compared to the number of nests within the colony). The overall proportions of flights generally reflected the proportions of the within-colony nest counts for the four most common species: Black-crowned Night-Heron ( Nycticorax nycticorax ), Cattle Egret ( Bubulcus ibis ), Great Egret ( Ardea alba ), and Snowy Egret ( Egretta thula ). Flightline surveys at Chase Lake indicated apparent variation related to the time of day and season, as well as a variation in detection of inbound and outbound adult ciconiiforms. For ciconiiforms at Chase Lake, the most appropriate combination of survey approaches will depend on the need for annual estimates of nest abundance of ciconiiform species, balanced with the financial, personnel, and logistical constraints associated with the survey methods. For ground-nesting American White Pelicans, the results from this study indicated that digital-image processing using remote-sensing software provides an accurate estimate of the number of American White Pelican nests. Estimates of the number of pelican nests from digital-image processing, using two commercially available remote-sensing software packages, produced nest estimates that were comparable to those of traditional manual counts from aerial photographs.

North Dakota↗

USGS2022

From flowering to foliage: Accelerometers track tree sway to provide high-resolution insights into tree phenology

Trees are bioindicators of global climate change and regional urbanization, but available monitoring tools are ineffective for fine-scale observation of many species. Using six accelerometers mounted on two urban ash trees ( Fraxinus americana ), we looked at high-frequency tree vibrations, or change in periodicity of tree sway as a proxy for mass changes, to infer seasonal patterns of flowering and foliage (phenophases). We compared accelerometer-estimated phenophases to those derived from digital repeat photography using Green Chromatic Coordinates (GCC) and visual observation of phenophases defined by the USA National Phenology Network (NPN). We also drew comparisons between two commercial accelerometers and assessed how placement height influenced the ability to extract seasonal transition dates. Most notably, tree sway data showed a greenness signal in an urban environment and produced a clear flowering time-series and peak flowering signal (PF), marking the first observations of a flower phenophase using accelerometer data. Estimated start of spring (SOS) from accelerometers and time-lapse GCC were more similar than start of autumn (SOA); accelerometers lagged behind the time-lapse camera dates by three and four days for SOS and 13 and 14 days for SOA for each tree. Estimates for SOS and SOA from accelerometers and time-lapse cameras aligned closely with different NPN phenophases. The two commercial accelerometers produced similar season onset: a difference of 2.4 to 3.8 days for SOS, 2.1 days for SOA, and 0.5 to 2.0 days for PF. Accelerometers placed at the main crown branch point versus higher in the canopy showed a difference of 0.2 to 4.9 days for SOS and -1.5 to 1.7 days for PF. Our results suggest accelerometers present a novel opportunity to objectively monitor reproductive tree biology and fill gaps in phenology observations. Furthermore, widely available accelerometers show promise for scaling up from individual trees to the landscape level to aid forest management and assessing climate change impacts to tree phenology.

Colorado↗

USGS2020

Persistence and plasticity in conifer water-use strategies

The selective use of seasonal precipitation by vegetation is critical to understanding the residence time and flow path of water in watersheds, yet there are limited datasets to test how climate alters these dynamics. Here, we use measurements of the seasonal cycle of tree ring 18O for two widespread conifer species in the Rocky Mountains of North America to provide a multi-decadal depiction of the seasonal origins of forest water use. The results show that while the conifer tree stands had a dominant preference for use of snowmelt, there were multi-annual periods over the last four decades when use of summer precipitation was preferential. Utilization of summer rain emerged during years with increased snowfall and tree growth, suggesting that summer rain enhanced the transpiration stream only during the periods of highest water use. We hypothesize this could be explained through shallowing of the root profile during wetter periods and/or through the influence of changing water table depths on the residence time of summer precipitation in the root zone. We suggest the tree ring proxy approach used here could be applied in other watersheds to provide critical insight into the temporal dynamics of plant water use that could not be inferred from short measurement campaigns. These data on the seasonal origins of forest water are critical for understanding forest vulnerability to drought, the processes that affect precipitation pathways and residence time in watersheds and the interpretation of tree ring proxy data.

Colorado↗