Geology topics

B. K. Sandercock

Publications and source records attributed to B. K. Sandercock.

5 recordsLinked to original sources

USGS2011

Spread of plague among black-tailed prairie dogs is associated with colony spatial characteristics

Sylvatic plague ( Yersinia pestis ) is an exotic pathogen that is highly virulent in black‐tailed prairie dogs ( Cynomys ludovicianus ) and causes widespread colony losses and individual mortality rates >95%. We investigated colony spatial characteristics that may influence inter‐colony transmission of plague at 3 prairie dog colony complexes in the Great Plains. The 4 spatial characteristics we considered include: colony size, Euclidean distance to nearest neighboring colony, colony proximity index, and distance to nearest drainage (dispersal) corridor. We used multi‐state mark–recapture models to determine the relationship between these colony characteristics and probability of plague transmission among prairie dog colonies. Annual mapping of colonies and mark–recapture analyses of disease dynamics in natural colonies led to 4 main results: 1) plague outbreaks exhibited high spatial and temporal variation, 2) the site of initiation of epizootic plague may have substantially influenced the subsequent inter‐colony spread of plague, 3) the long‐term effect of plague on individual colonies differed among sites because of how individuals and colonies were distributed, and 4) colony spatial characteristics were related to the probability of infection at all sites although the relative importance and direction of relationships varied among sites. Our findings suggest that conventional prairie dog conservation management strategies, including promoting large, highly connected colonies, may need to be altered in the presence of plague.

Colorado, Oklahoma, Texas, Kansas, New Mexico↗

USGS2011

Scale-dependent factors affecting North American river otter distribution in the midwest

The North American river otter ( Lontra canadensis ) is recovering from near extirpation throughout much of its range. Although reintroductions, trapping regulations and habitat improvements have led to the reestablishment of river otters in the Midwest, little is known about how their distribution is influenced by local- and landscape-scale habitat. We conducted river otter sign surveys from Jan. to Apr. in 2008 and 2009 in eastern Kansas to assess how local- and landscape-scale habitat factors affect river otter occupancy. We surveyed three to nine 400-m stretches of stream and reservoir shorelines for 110 sites and measured local-scale variables ( e.g., stream order, land cover types) within a 100 m buffer of the survey site and landscape-scale variables ( e.g., road density, land cover types) for Hydrological Unit Code 14 watersheds. We then used occupancy models that account for the probability of detection to estimate occupancy as a function of these covariates using Program PRESENCE. The best-fitting model indicated river otter occupancy increased with the proportion of woodland cover and decreased with the proportion of cropland and grassland cover at the local scale. Occupancy also increased with decreased shoreline diversity, waterbody density and stream density at the landscape scale. Occupancy was not affected by land cover or human disturbance at the landscape scale. Understanding the factors and scale important to river otter occurrence will be useful in identifying areas for management and continued restoration.

Kansas↗

USGS2010

Exposure of nonbreeding migratory shorebirds to cholinesterase-inhibiting contaminants in the western hemisphere

Migratory shorebirds frequently forage and roost in agricultural habitats, where they may be exposed to cholinesterase-inhibiting pesticides. Exposure to organophosphorus and carbamate compounds, common anti-cholinesterases, can cause sublethal effects, even death. To evaluate exposure of migratory shorebirds to organophosphorus and carbamates, we sampled birds stopping over during migration in North America and wintering in South America. We compared plasma cholinesterase activities and body masses of individuals captured at sites with no known sources of organophosphorus or carbamates to those captured in agricultural areas where agrochemicals were recommended for control of crop pests. In South America, plasma acetylcholinesterase and butyrylcholinesterase activity in Buff-breasted Sandpipers was lower at agricultural sites than at reference sites, indicating exposure to organophosphorus and carbamates. Results of plasma cholinesterase reactivation assays and foot-wash analyses were inconclusive. A meta-analysis of six species revealed no widespread effect of agricultural chemicals on cholinesterase activity. however, four of six species were negative for acetylcholinesterase and one of six for butyrylcholinesterase, indicating negative effects of pesticides on cholinesterase activity in a subset of shorebirds. Exposure to cholinesterase inhibitors can decrease body mass, but comparisons between treatments and hemispheres suggest that agrochemicals did not affect migratory shorebirds' body mass. Our study, one of the first to estimate of shorebirds' exposure to cholinesterase-inhibiting pesticides, suggests that shorebirds are being exposed to cholinesterase- inhibiting pesticides at specific sites in the winter range but not at migratory stopover sites. future research should examine potential behavioral effects of exposure and identify other potential sitesand levels of exposure. ?? The Cooper Ornithological Society 2010.

Condor↗

USGS2002

Genetic parentage and mate guarding in the Arctic-breedng Western Sandpiper

Extrapair copulations and fertilizations are common among birds, especially in passerines. So far, however, few studies have examined genetic mating systems in socially monogamous shorebirds. Here, we examine parentage in the Western Sandpiper ( Calidris mauri ). Given that Western Sandpipers nest at high densities on the Arctic tundra, have separate nesting and feeding areas, and show high divorce rates between years, we expected extrapair paternity to be more common in this species compared to other monogamous shorebirds. However, DNA fingerprinting of 98 chicks from 40 families revealed that only 8% of broods contained young sired by extrapair males, and that 5% of all chicks were extrapair. All chicks were the genetic offspring of their social mothers. We found that males followed females more often than the reverse. Also, cuckolded males were separated from their mates for longer than those that did not lose paternity. Although these results suggest a role for male mate guarding, we propose that high potential costs in terms of reduced paternal care likely constrain female Western Sandpipers from seeking extrapair copulations.

The Auk↗

USGS2000

Do male breeding displays function to attract mates or defend territories? The explanatory role of mate and site fidelity

Many shorebirds show elaborate breeding displays that include aerial flights and ground displays accompanied by song. The mate attraction hypothesis suggests that breeding displays function to attract mates and maintain pair bonds, whereas the territory defense hypothesis suggests breeding displays function in defining and defending nesting and feeding territories. We tested these hypotheses in the Western Sandpiper ( Calidris mauri ) by contrasting the duration and level of male breeding displays among pairs that differed in their mate and site fidelity. As predicted by the mate attraction hypothesis, males performed the highest number of song sequences during pair formation, and males paired with their mate of a prior year sang less than males paired to new mates. Further, sitefaithful males mated to a new but experienced mate displayed significantly more than remated males or males new to the area. This suggests a male's prior familiarity with an area and his neighbors does not lessen his display rate as was predicted under the territory defense hypothesis. Limited support for the territory defense hypothesis came from observations of males performing breeding displays with neighboring males along nest territory boundaries. This behavior was short-lived, however, as males abandoned nesting areas after pair-formation and used adjacent or disjointed feeding areas during egg-laying and incubation. Male aggression (i.e., aerial and ground chases), as opposed to breeding displays, appeared to be the principal means of maintaining territory boundaries. Indeed, the rate at which males chased other males remained fairly constant and high throughout the breeding season. Male chasing behavior may also serve as a paternity guard to protect against extra-pair copulations. Our study also found that a female's prior breeding experience in an area correlated with a reduced display rate by her mate, particularly if that mate was new to the area. This indicates female characteristics may not only drive nest initiation, as has been shown in other studies, but are important in determining the duration and extent of male display.

Alaska↗