J. Turner | Geology Reports

USGS2014

Raptor abundance and northern bobwhite survival and habitat use

Predation risk has a profound influence on prey behavior and habitat use. The Rio Grande Plains ecoregion of Texas, USA, provides a unique opportunity to investigate changes in prey behavior because the ecoregion experiences a high influx of raptors every year during autumn migration. We used an 8-year data set (2000–2008) of radiocollared northern bobwhites ( Colinus virginianus ) and raptor abundance to test the hypothesis that bobwhites responded to increased raptor abundance via changes in woody-cover use at the home-range scale. Bobwhite survival was negatively correlated with raptor abundance, with red-tailed hawks ( Buteo jamaicensis ), and northern harriers ( Circus cyaneus ) accounting for 51% of the variability in bobwhite survival ( P  < 0.010). However, we documented no change in the amount of woody cover used by bobwhites in their home range between the raptor migration (6.6% ± 0.5%; n  = 73 bobwhites) and non-migration periods (7.1% ± 0.4%; n  = 105 bobwhites; P  = 0.490). In addition, bobwhites that survived the raptor migration period used similar amounts of woody cover within their home range (6.3% ± 0.6%, n  = 58 bobwhites) compared with those dying during the migration period (6.8% ± 0.4%, n  = 100 bobwhites; P  = 0.530). Our data suggest that bobwhites do not alter their use of woody cover at the home-range scale in response to increasing raptor abundance, but this does not preclude increased use of woody cover at the point-of-use scale.

Texas↗

USGS2006

Future trends in transport and fate of diffuse contaminants in catchments, with special emphasis on stable isotope applications

A summary is provided of the first of a series of proposed Integrated Science Initiative workshops supported by the UNESCO International Hydrological Programme. The workshop brought together hydrologists, environmental chemists, microbiologists, stable isotope specialists and natural resource managers with the purpose of communicating new ideas on ways to assess microbial degradation processes and reactive transport at catchment scales. The focus was on diffuse contamination at catchment scales and the application of compound-specific isotope analysis (CSIA) in the assessment of biological degradation processes of agrochemicals. Major outcomes were identifying the linkage between water residence time distribution and rates of contaminant degradation, identifying the need for better information on compound specific microbial degradation isotope fractionation factors and the potential of CSIA in identifying key degradative processes. In the natural resource management context, a framework was developed where CSIA techniques were identified as practically unique in their capacity to serve as distributed integrating indicators of process across a range of scales (micro to diffuse) of relevance to the problem of diffuse pollution assessment. Copyright ?? 2006 John Wiley & Sons, Ltd.

Hydrological Processes↗