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At least 37 records · Page 2Linked to original sources
USGS2026

Why are ornithological studies so focused on the breeding stage? A test of hypotheses

Unequal representation of focal research areas can arise during the initial stages of project development when investigators make decisions about what, when, and where to study. Regarding when research is conducted, publications on vertebrates are strongly skewed toward breeding-stage studies, leaving sizeable gaps in our knowledge pertaining to behavior and demography in nonbreeding stages. Here, we quantified how the focus on different annual cycle stages has changed over the past 64 years in the field of ornithology, and tested 3 hypotheses to explain underlying correlates of the focus on different stages. We surveyed field-based studies published in Ornithology from 1960 to 2024 and documented the annual cycle stages examined, regions of study, migratory strategies of focal species, and author affiliation for each paper. The tendency to conduct breeding-stage research in ornithology became more, rather than less, pronounced over the 64-year interval, and breeding-stage research was more common when field work focused on migratory species. Therefore, investigators, authors, and editors could likely increase representation of other annual-cycle stages by supporting, conducting, and publishing more studies in the tropics and more studies using remote tracking technologies. More nonbreeding and year-round studies are necessary to fully understand the ecology and evolution of species and develop the most effective strategies for conservation.

Ornithology↗
USGS1995

Simulation of stage and the the hydrologic budget of Devils Lake, Sauk County, Wisconsin

Water clarity of Devils Lake, in the Driftless Area of southwestern Wisconsin, has been decreasing because of blue-green algal blooms. An understanding of the hydrology of Devils Lake is needed to develop a mitigation plan to reduce phosphorus input. A model was developed to test the current understanding of the hydrology of the lake including stage and hydrologic budget and to estimate the effects of proposed mitigation plans on lake stage. Daily lake stage was simulated in the model by summing estimates of hydrologic-budget components. The Devils Lake hydrologic-budget components are precipitation on the lake surface, evaporation from the lake surface, runoff (consisting of overland flow to the lake and an intermittent stream flowing into the lake), and ground-water flow into and out of the lake. The model was calibrated to measured lake stage for the period 1980-92. Simulated stage compares reasonably well with historical stage data for Devils Lake. The root mean square of the differences of simulated and measured daily lake stages for the period 1980-92 is 0.83 foot. Simulated lake stage is very sensitive to small changes in runoff and evaporation coefficients, and ground-waterflow rates used in the model. The average model-calculated annual amounts of each hydrologic-budget component for the 1980-92 simulation period, in order of increasing volume, are evaporation (791 acre-feet), precipitation (973 acre-feet), runoff (1,107 acre-feet), and net ground-water flow, which is out of the lake (1,323 acre-feet). Three mitigation plans were simulated. Mitigation plan 3, which includes the addition of water from a basin adjacent to the northeastern side of the Devils Lake Basin, allows for withdrawals of hypolimnetic water and maintaining lake stage closer to optimal levels than would result without mitigation.

Wisconsin↗
USGS2025

Dynamic rating method for computing discharge and stage from time-series data

Ratings are used for several reasons in water-resources investigations. The simplest rating relates discharge to the stage of a river (the stage-discharge relation). From a pure hydrodynamics perspective, all rivers and streams have some form of hysteresis in the relation between stage and discharge because flow becomes unsteady as a flood wave passes. The stage-discharge relation is unable to represent hysteresis. However, a dynamic rating method can capture hysteresis, which is driven by the variable energy slope of a flood wave. A dynamic rating method called DYNPOUND, which accommodates compact and compound channel geometry, was developed by simplifying the one-dimensional Saint-Venant equations. The DYNPOUND method was developed in the Python programming language and computes discharge from stage and stage from discharge. Stage and discharge time series computed with this dynamic rating method were compared to the U.S. Geological Survey (USGS) published stage and discharge time series. The results from the DYNPOUND method were also compared to in-person field measurements of stage and discharge made at 10 USGS streamgages. DYNPOUND was calibrated for 10 USGS streamgages using published discharge time-series data computed with a simple rating method. The calibration objective was to minimize the mean squared logarithmic error (MSLE) of the DYNPOUND-computed discharge with respect to the discharge time series computed by a simple rating method. For each site, the calibration process also included comparing all field measurements within a selected water year to the corresponding DYNPOUND-computed discharge data points. The MSLE of the DYNPOUND-computed discharge time series for the 10 sites ranged from 8.51×10 −4 to 1.36×10 −1 . For each site, an event-based period was selected to compare the discharge time series computed with the dynamic rating method to discharge field measurements made at the streamgages; the range of MSLE for the 10 DYNPOUND-computed discharge sites was from 4.79×10 −4 to 2.30×10 −2 .

continental United States↗
USGS1999

Simulation of stage and hydrologic budget for Shell Lake, Washburn County, Wisconsin

A model that simulates lake stage was developed to test the current understanding of the hydrology of Shell Lake, Wisconsin and to provide a tool for predicting the effects of withdrawing lake water on future lake stages. The model code is written in Fortran and simulates daily lake stage by summing estimates of hydrologic-budget components - precipitation falling on the lake surface, water evaporating from the lake surface, runoff (consisting of overland flow to the lake and intermittent streams flowing into the lake), and ground-water flow out of the lake. The model was calibrated to intermittent lake stage measurements for the period 1948-98. The hydrologic budget model was coupled to UCODE, a parameter estimation model, to aid in estimating runoff coefficients. Trends in stage simulated by the calibrated model compare reasonably well with historical stage trends. The root mean square of the differences of simulated and measured daily lake stage for the period 1948-98 is 0.54 foot. Predictive simulations indicate that withdrawing lake water is an effective way of reducing lake stage. Several years of pumping for at least 200 days per year at rates of 1,000 to 2,000 gallons per minute would have been required to reduce 1990's high stages by about one foot.

Wisconsin↗
USGS2014

Comparative responses to endocrine disrupting compounds in early life stages of Atlantic salmon, Salmo salar

Atlantic salmon (Salmo salar) are endangered anadromous fish that may be exposed to feminizing endocrine disrupting compounds (EDCs) during early development, potentially altering physiological capacities, survival and fitness. To assess differential life stage sensitivity to common EDCs, we carried out short-term (four day) exposures using three doses each of 17α-ethinylestradiol (EE2), 17β-estradiol (E2), and nonylphenol (NP) on four early life stages; embryos, yolk-sac larvae, feeding fry and one year old smolts. Differential response was compared using vitellogenin (Vtg, a precursor egg protein) gene transcription. Smolts were also examined for impacts on plasma Vtg, cortisol, thyroid hormones (T4/T3) and hepatosomatic index (HSI). Compound-related mortality was not observed in any life stage, but Vtg mRNA was elevated in a dose-dependent manner in yolk-sac larvae, fry and smolts but not in embyos. The estrogens EE2 and E2 were consistently stronger inducers of Vtg than NP. Embryos responded significantly to the highest concentration of EE2 only, while older life stages responded to the highest doses of all three compounds, as well as intermediate doses of EE2 and E2. Maximal transcription was greater for fry among the three earliest life stages, suggesting fry may be the most responsive life stage in early development. Smolt plasma Vtg was also significantly increased, and this response was observed at lower doses of each compound than was detected by gene transcription suggesting this is a more sensitive indicator at this life stage. HSI was increased at the highest doses of EE2 and E2 and plasma T3 decreased at the highest dose of EE2. Our results indicate that all life stages after hatching are potentially sensitive to endocrine disruption by estrogenic compounds and that physiological responses were altered over a short window of exposure, indicating the potential for these compounds to impact fish in the wild.

Aquatic Toxicology↗
USGS1998

Species-environment relationships and vegetation patterns: Effects of spatial scale and tree life-stage

Do relationships between species and environmental gradients strengthen or weaken with tree life-stage (i.e., small seedlings, large seedlings, saplings, and mature trees)? Strengthened relationships may lead to distinct forest type boundaries, or weakening connections could lead to gradual ecotones and heterogeneous forest landscapes. We quantified the changes in forest dominance (basal area of tree species by life-stage) and environmental factors (elevation, slope, aspect, intercepted photosynthetically active radiation (PAR), summer soil moisture, and soil depth and texture) across 14 forest ecotones (n = 584, 10 m x 10 m plots) in Rocky Mountain National Park, Colorado, U.S.A. Local, ecotone-specific species-environment relationships, based on multiple regression techniques, generally strengthened from the small seedling stage (multiple R2 ranged from 0.00 to 0.26) to the tree stage (multiple R2 ranged from 0.20 to 0.61). At the landscape scale, combined canonical correspondence analysis (CCA) among species and for all tree life-stages suggested that the seedlings of most species became established in lower-elevation, drier sites than where mature trees of the same species dominated. However, conflicting evidence showed that species-environment relationships may weaken with tree life-stage. Seedlings were only found in a subset of plots (habitats) occupied by mature trees of the same species. At the landscape scale, CCA results showed that species-environment relationships weakened somewhat from the small seedling stage (86.4% of the variance explained by the first two axes) to the tree stage (76.6% of variance explained). The basal area of tree species co-occurring with Pinus contorta Doug. ex. Loud declined more gradually than P. contorta basal area declined across ecotones, resulting in less-distinct forest type boundaries. We conclude that broad, gradual ecotones and heterogeneous forest landscapes are created and maintained by: (1) sporadic establishment of seedlings in sub-optimal habitats; (2) survivorship of saplings and mature trees in a wider range of environmental conditions than seedlings presently endure; and (3) the longevity of trees and persistence of tree species in a broad range of soils, climates, and disturbance regimes.

Plant Ecology↗
USGS2014

Size-selective mortality of steelhead during freshwater and marine life stages related to freshwater growth in the Skagit River, Washington

We evaluated freshwater growth and survival from juvenile (ages 0–3) to smolt (ages 1–5) and adult stages in wild steelhead Oncorhynchus mykiss sampled in different precipitation zones of the Skagit River basin, Washington. Our objectives were to determine whether significant size-selective mortality (SSM) in steelhead could be detected between early and later freshwater stages and between each of these freshwater stages and returning adults and, if so, how SSM varied between these life stages and mixed and snow precipitation zones. Scale-based size-at-annulus comparisons indicated that steelhead in the snow zone were significantly larger at annulus 1 than those in the mixed rain–snow zone. Size at annuli 2 and 3 did not differ between precipitation zones, and we found no precipitation zone × life stage interaction effect on size at annulus. Significant freshwater and marine SSM was evident between the juvenile and adult samples at annulus 1 and between each life stage at annuli 2 and 3. Rapid growth between the final freshwater annulus and the smolt migration did not improve survival to adulthood; rather, it appears that survival in the marine environment may be driven by an overall higher growth rate set earlier in life, which results in a larger size at smolt migration. Efforts for recovery of threatened Puget Sound steelhead could benefit by considering that SSM between freshwater and marine life stages can be partially attributed to growth attained in freshwater habitats and by identifying those factors that limit growth during early life stages.

Washington↗
USGS1973

Toxicity of TFM (lampricide) to six early stages of rainbow trout (Salmo gairdneri)

The lampricide TFM (3-trifluoromethyl-4-nitrophenol) was tested against the following life stages of rainbow trout ( Salmo gairdneri ): green eggs, eyed eggs, sac fry, swim-up fry, fry, and fingerlings in four water hardnesses (12, 44, 170, and 320 mg/liter as CaCO 3 ). The eyed-egg stage was one of the most resistant stages tested, and the sac-fry stage was one of the least resistant. Increased water hardness decreases toxicity to all stages. The LC50’s range from 0.532 mg/liter to 40.0 mg/liter depending upon life stage, water hardness, and duration of exposure. The margin of safety for coexisting species exposed to TFM ranges from 3.2 to 4.1 in natural waters. The margin of safety for early life stages of rainbow trout and larval lamprey under controlled laboratory conditions ranges from 4.2 to 12.2. Therefore, all six early life stages of rainbow trout are safe in minimum lampricidal concentrations of TFM.

Journal of the Fisheries Research Board of Canada↗
USGS2007

Peak stages from backwater conditions at streamflow-gaging stations in and near South Dakota through water year 2001

Stream stages associated with the annual peak discharge are presented for 182 streamflow-gaging stations in and near South Dakota. The peak stage at a station can occur as the result of the annual maximum discharge, but also as the result of backwater conditions. Backwater, often caused by ice, can produce a peak stage higher than the stage coincident with annual maximum discharge. The U.S. Geological Survey has cooperated with the South Dakota Department of Transportation to prepare this report, which provides a summary of peak-stage data through water year 2001 for gaging stations in and near South Dakota where annual peak stages resulting from backwater conditions have exceeded stages associated with annual peak discharge by as much as several feet. Where applicable, data summaries include the flood stage that is assigned by the National Weather Service.

South Dakota↗
USGS2015

csa2sac—A program for computing discharge from continuous slope-area stage data

Introduction Continuous Slope-Area (CSA) gages were developed by the Arizona Water Science Center to enable the estimation of hydrographs when direct measurements of discharge cannot be made (Smith and others, 2010). CSA gages extend standard U.S. Geological Survey (USGS) methods for determining peak discharges to mid and high flows over a hydrograph computed at regular intervals with indirect measurement methods (Benson and Dalrymple, 1967; Dalrymple and Benson, 1967). CSA gages combine continuous stage records at two or more (typically three or four) cross sections with crosssection surveys and estimates of channel roughness to compute discharge over a range of flows. With standard indirect methods of determining peak discharge, water-surface elevation in the study reach at the peak flow is estimated from surveys of debris associated with the peak-flow water line. With CSA gages, stages are continuously measured at the cross sections, at regular and synchronized intervals (typically 5 minutes) over a flow event, and discharge can be calculated at each interval. Calculation of discharge using indirect methods has been automated with the slope-area computation (SAC) program (Fulford, 1994). SAC is a widely used program within the USGS; it is easily run and displays output in a clear and convenient format, which includes flags that alert the user to shortcomings in the calculation. Use of SAC has been facilitated by SACGUI (Bradley, 2012; SACGUI uses a version of SAC called SAC7), a user interface that directly reads and displays survey data, allows for specification of water-surface slope and channel roughness, writes the input file for SAC7, runs SAC7, and displays SAC7 output. csa2sac is a program (appendix 1) that repeatedly runs SAC7 using stage data and a SAC7 input template file to compute the discharge at CSA gages. It is written in the C programming language, and is compatible with 64-bit Windows operating systems. The program reads a SAC7 input file and a file containing stage-data time series. It writes a new version of the SAC7 input file with the stage data for one time step, runs SAC7, then extracts computed discharges from the SAC7 output file and collates the discharges and stages to a separate file. It repeats these steps for each time interval in the stage file to produce a discharge time series from the stage data. csa2sac has been tested with two, three, four, and six cross sections and found to operate successfully. By running SAC7, csa2sac maintains consistency and comparability of both discharges calculated from CSA gages and of standard USGS methods for computing discharges indirectly. Brown and Metcalfe (2014) have made available alternative software for producing CSA discharges. In addition to csa2sac, the SAC7 program is required. It is the same as the original SAC program, except that it is compiled for 64-bit Windows operating systems and has a slightly different command line input. It is available online (http://water.usgs.gov/software/SAC/) as part of the SACGUI installation program. The program name, “SAC7.exe,” is coded into csa2sac, and must not be changed.

Open-File Report↗
USGS1965

The operation and maintenance of a crest-stage gaging station

The purpose of this manual is to familiarize field personnel with the procedures involved in operating crest-stage gaging stations. Crest-stage gages are used to determine the elevation of a peak stage occurring at a specific location in a stream. A crest-stage gage consists of a length of 14-inch diameter pipe installed in a vertical position in the stream channel (figure 1). The pipe is vented and equipped with an intake system that allows water to enter and leave the pipe as the stream rises and recedes. An equal length of aluminum "T" channel (staff) is inserted in the pipe and made to rest on a positive stop called a datum pin. When granulated cork is placed in the gage, the cork will float on the rising stage, then adhere to the staff after the stage recedes. The peak stage is then determined by removing the staff and measuring the distance between the cork line and the lower end of the staff. The primary purpose of a crest-stage gaging station is to collect hydrologic data for flood-frequency analyses. Collection of data for such analyses involves operating a network of stations for a period of years until sufficient peak flow data are obtained to accurately define flood-frequency curves. Because carelessness in collecting data at the gage site might result in the loss of an entire year's flood event, the importance of proper operation and maintenance of these gages can not be overemphasized. Peak discharges are related to the basin characteristics and major changes in these characteristics must be evaluated. For€st fires, timber harvest, or a new road location that alters the natural drainage of the basin, may effect the intensity and timing of the runoff of the basin. Rigid datum controls must be maintained at the gage site throughout the period of record. Physical changes of the site resulting from flood flows or manmade alterations must be evaluated. If a drainage structure such as a culvert is part of the site features, free-flow conditions must be maintained or obstructions carefully documented.

Open-File Report↗
USGS1985

Stage fluctuations of Wisconsin lakes

This report describes lake-stage fluctuations of 83 gaged lakes in Wisconsin and presents techniques for estimating stage fluctuation at ungaged lakes. Included are stage information at 83 lakes and stage-frequency data for 32 of these lakes that had sufficient record for analysis. Lakes are classified by a hydrologic-topographic lake classification scheme as ground-water flowthrough (GWF) lakes, surface-water drainage (SWD) lakes, and surface-water flow-through (SWF) lakes. Lakes within the same class were found to have similar water-level fluctuations. The lake-stage records indicate that most annual maximums occur during the months of May and June for all three classes. Annual minimum lake levels generally occur in September for surface-water drainage lakes, in March for surface-water flowthrough lakes, and in November for ground-water flow-through lakes. Data for each lake include location, period of water-level record, hydrologic classification, drainage area, surface area, lake volume, maximum depth, long-term mean stage and its standard deviation, maximum and minimum observed lake stage, and the average annual lake-stage fluctuation.

Wisconsin↗
USGS2026

Carryover effects across juvenile periods vary by species, cause-specific mortality, and stage-specific behavior

Conditions during one life-stage can carry over to influence fitness outcomes in later stages. How carryover effects manifest, however, may vary depending on the type and magnitude of risks that animals face in subsequent life-stages. The influence of carryover effects on cause-specific mortality remains largely unclear, particularly during vulnerable life-stages, including juvenile periods. We proposed and investigated the Cause-specific carryover hypothesis, that the relative influence of traits developed during a previous stage on mortality during the next vary by cause of mortality, using juvenile sagebrush songbirds (Brewer’s sparrow, Spizella breweri ; sagebrush sparrow, Artemisiospiza nevadensis ; sage thrasher, Oreoscoptes montanus ) as a focal system. We tracked birds during the post-fledging period (a juvenile period following the nestling period), identified the rates and causes of mortality, and tested the relative influence of different nestling traits (wing length, tarsus length, feather development, and body condition) on post-fledging mortality risk. Carryover effects varied across co-occurring species and differed by cause of mortality, and tarsus length had an unexpected and outsized impact on predation risk in the two sparrows. Although wing morphology typically is considered the most important trait for mobility in birds, most mortalities occurred during the first 5 days of the post-fledging period when altricial fledglings were incapable of flight and likely relied on running or scrambling ability to escape predators. Therefore, carryover effects were driven by stage-specific behavior during the period of highest risk. Developing animals may face investment trade-offs between morphological traits that influence different types of risk during different subsequent stages.

Wyoming↗
USGS2026

Two-stage approach to automatic detection with machine learning for improved surveillance of the invasive Cuban treefrog

The Cuban treefrog ( Osteopilus septentrionalis ), as an invasive species in the southern United States, presents a need for effective surveillance. Automated detection expedites processing of audio data for large-scale surveillance and monitoring programs. However, current available methods commonly used for anuran species have not been sufficient to detect Cuban treefrogs. Here, we present results from a two-stage method for automated detection that employs both cross-correlation template matching and secondary supervised learning classifiers. In the first stage, audio data are screened for initial detections using template matching, in which the detections contain both true and false positives. In the second stage, the false positives are screened out using classifier algorithms. We used this method to process 139,985 audio recordings, consisting of 596,046 total minutes, collected at 13 locations in Louisiana and Florida from 2014 to 2022. From the stage 1 template matching, we detected 83,191 Cuban treefrog signals across recordings. The stage 2 machine learning model was able to identify stage 1 false positive detections with a testing accuracy of 98.46% and a testing false positive rate of 1.116%. After pruning false positive detections, a total of 20,271 individual Cuban treefrog detections remained, distributed mainly across 3 sites in an area with known presence. Locations with presumed absence had an easily verifiable number of false positive detections ( n = 109 across all other sites). The two-stage methodology utilizing both template matching and machine learning algorithms can be integrated into wildlife surveillance or monitoring programs for species with distinctive, conserved calls as an effective way to achieve sensitive species detection with a low incidence of false positives.

Florida, Louisiana↗
USGS2015

Factors influencing recruitment of walleye and white bass to three distinct early ontogenetic stages

Determining the factors that influence recruitment to sequential ontogenetic stages is critical for understanding recruitment dynamics of fish and for effective management of sportfish, particularly in dynamic and unpredictable environments. We sampled walleye ( Sander vitreus ) and white bass ( Morone chrysops ) at 3 ontogenetic stages (age 0 during spring: ‘age-0 larval’; age 0 during autumn: ‘age-0 juvenile’; and age 1 during autumn: ‘age-1 juvenile’) from 3 reservoirs. We developed multiple linear regression models to describe factors influencing age-0 larval, age-0 juvenile and age-1 juvenile walleye and white bass abundance indices. Our models explained 40–80% (68 ± 9%; mean ± SE) and 71%–97% (81 ± 6%) of the variability in catch for walleye and white bass respectively. For walleye, gizzard shad were present in the candidate model sets for all three ontogenetic stages we assessed. For white bass, there was no unifying variable in all three stage-specific candidate model sets, although walleye abundance was present in two of the three white bass candidate model sets. We were able to determine several factors affecting walleye and white bass year-class strength at multiple ontogenetic stages; comprehensive analyses of factors influencing recruitment to multiple early ontogenetic stages are seemingly rare in the literature. Our models demonstrate the interdependency among early ontogenetic stages and the complexities involved with sportfish recruitment.

Ecology of Freshwater Fish↗
USGS2021

Breeding season space use by lesser prairie-chickens (Tympanuchus Pallidicinctus) varies among ecoregions and breeding stages

Large-scale declines of grassland ecosystems in the conterminous United States since European settlement have led to substantial loss and fragmentation of lesser prairie-chicken ( Tympanuchus pallidicinctus ) habitat and decreased their occupied range and population numbers by ∼85%. Breeding season space use is an important component of lesser prairie-chicken conservation, because it could affect both local carrying capacity and population dynamics. Previous estimates of breeding season space use are largely limited to one of the four currently occupied ecoregions, but potential extrinsic drivers of breeding space use, such as landscape fragmentation, vegetation structure and composition, and density of anthropogenic structures, can show large spatial variation. Moreover, habitat needs vary greatly among the lekking/prelaying, nesting, brood-rearing, and postbreeding stages of the breeding season, but space use by female lesser prairie-chickens during these stages remain relatively unclear. We tested whether home range area and daily displacement (the net distance between the first and last location of each day) of female lesser prairie-chickens varied among ecoregions and breeding stages at four study sites in Kansas and Colorado, U.S.A., representing three of the four currently occupied ecoregions. We equipped females with very-high-frequency (VHF) or Global Positioning System (GPS) transmitters, and estimated home range area with kernel density estimators or biased random bridge models, respectively. Across all ecoregions, breeding season home range area averaged 190.4 ha (±19.1 ha se ) for birds with VHF and 283.6 ha (±23.1 ha) for birds with GPS transmitters, whereas daily displacement averaged 374.8 m (±14.3 m). Average home range area and daily displacement of bird with GPS transmitters were greater in the Short-Grass Prairie/ Conservation Reserve Program Mosaic and Sand Sagebrush Prairie Ecoregions compared to sites in the Mixed-Grass Prairie Ecoregion. Home range area and daily displacement were greatest during lekking/prelaying and smallest during the brood-rearing stage, when female movements were restricted by mobility of chicks. Ecoregion- and breeding stage-specific estimates of space use by lesser prairie-chickens will help managers determine the spatial configuration of breeding stage-specific habitat on the landscape. Furthermore, ecoregion- and breeding stage-specific estimates are crucial when estimating the amount of breeding habitat needed for lesser prairie-chicken populations to persist.

Colorado↗
USGS2000

Modeling and estimation of stage-specific daily survival probabilities of nests

In studies of avian nesting success, it is often of interest to estimate stage-specific daily survival probabilities of nests. When data can be partitioned by nesting stage (e.g., incubation stage, nestling stage), piecewise application of the Mayfield method or Johnson's method is appropriate. However, when the data contain nests where the transition from one stage to the next occurred during the interval between visits, piecewise approaches are inappropriate. In this paper, I present a model that allows joint estimation of stage-specific daily survival probabilities even when the time of transition between stages is unknown. The model allows interval lengths between visits to nests to vary, and the exact time of failure of nests does not need to be known. The performance of the model at various sample sizes and interval lengths between visits was investigated using Monte Carlo simulations, and it was found that the model performed quite well: bias was small and confidence-interval coverage was at the nominal 95% rate. A SAS program for obtaining maximum likelihood estimates of parameters, and their standard errors, is provided in the Appendix.

Ecology↗
USGS2010

Multi-stage origin of the Coast Range ophiolite, California: Implications for the life cycle of supra-subduction zone ophiolites

The Coast Range ophiolite of California is one of the most extensive ophiolite terranes in North America, extending over 700 km from the northernmost Sacramento Valley to the southern Transverse Ranges in central California. This ophiolite, and other ophiolite remnants with similar mid-Jurassic ages, represent a major but short-lived episode of oceanic crust formation that affected much of western North America. The history of this ophiolite is important for models of the tectonic evolution of western North America during the Mesozoic, and a range of conflicting interpretations have arisen. Current petrologic, geochemical, stratigraphic, and radiometric age data all favor the interpretation that the Coast Range ophiolite formed to a large extent by rapid extension in the forearc region of a nascent subduction zone. Closer inspection of these data, however, along with detailed studies of field relationships at several locales, show that formation of the ophiolite was more complex, and requires several stages of formation. Our work shows that exposures of the Coast Range ophiolite preserve evidence for four stages of magmatic development. The first three stages represent formation of the ophiolite above a nascent subduction zone. Rocks associated with the first stage include ophiolite layered gabbros, a sheeted complex, and volcanic rocks vith arc tholeiitic or (roore rarely) low-K calc-alkaline affinities. The second stage is characterized by intrusive wehrlite-clinopyroxenite complexes, intrusive gabbros, Cr-rich diorites, and volcanic rocks with high-Ca boninitic or tholeiitic ankaramite affinities. The third stage includes diorite and quartz diorite plutons, felsic dike and sill complexes, and calc-alkaline volcanic rocks. The first three stages of ophiolite formation were terminated by the intrusion of mid-ocean ridge basalt dikes, and the eruption of mid-ocean ridge basalt or ocean-island basalt volcanic suites. We interpret this final magmatic event (MORB dikes) to represent the collision of an active spreading ridge. Subsequent reorganization of relative plate motions led to sinistral transpression, along with renewed subduction and accretion of the Franciscan Complex. The latter event resulted in uplift and exhumation of the ophiolite by the process of accretionary uplift.

California↗