Geology topics

Mark A. Ricca

Publications and source records attributed to Mark A. Ricca.

59 records · Page 4Linked to original sources

USGS2009

Salton Sea Ecosystem Monitoring Project

The Salton Sea is critically important for wintering and breeding waterbirds, but faces an uncertain future due to water delivery reductions imposed by the Interstate and Federal Quantification Settlement Agreement of 2003. The current preferred alternative for wetland restoration at the Salton Sea is saline habitat impoundments created to mitigate the anticipated loss of wetland habitat. In 2006, a 50-hectare experimental complex that consisted of four inter-connected, shallow water saline habitat ponds (SHP) was constructed at the southeastern shoreline of the Salton Sea and flooded with blended waters from the Alamo River and Salton Sea. The present study evaluated ecological risks and benefits of the SHP concept prior to widespread restoration actions. This study was designed to evaluate (1) baseline chemical, nutrient, and contaminant measures from physical and biological constituents, (2) aquatic invertebrate community structure and colonization patterns, and (3) productivity of and contaminant risks to nesting waterbirds at the SHP. These factors were evaluated and compared with those of nearby waterbird habitat, that is, reference sites.

Open-File Report↗

USGS2009

Use of a nesting platform by Gull-billed Terns and Black Skimmers at the Salton Sea, California

In 2006, we constructed an elevated nesting platform at the Salton Sea, California, and monitored its use by Gull-billed Terns and Black Skimmers over three subsequent breeding seasons. Black Skimmers were the first to colonize the platform with a total of five nests in 2006. In 2007 Gull-billed Terns colonized the platform with a total of 28 nests and the number of Black Skimmer nests increased to 20. Neither species nested on the platform in 2008. Low success for both species was probably influenced by at least two factors. First, when both species nested on the platform, nest densities were higher than is typical of their colonies on larger, earthen islands, and colony success may have been reduced by overcrowding. Second, lack of access to water may have reduced chicks' ability to thermoregulate effectively in the hot environment of the Salton Sea. Refinements to the size, design, and location of artificial nesting habitats are necessary to enhance productivity of colonial groundnesting birds at the Salton Sea successfully.

Western Birds↗

USGS2008

Sources of organochlorine contaminants and mercury in seabirds from the Aleutian archipelago of Alaska: Inferences from spatial and trophic variation

Persistent organochlorine compounds and mercury (Hg) have been detected in numerous coastal organisms of the Aleutian archipelago of Alaska, yet sources of these contaminants are unclear. We collected glaucous-winged gulls, northern fulmars, and tufted puffins along a natural longitudinal gradient across the western and central Aleutian Islands (Buldir, Kiska, Amchitka, Adak), and an additional 8 seabird species representing different foraging and migratory guilds from Buldir Island to evaluate: 1) point source input from former military installations, 2) westward increases in contaminant concentrations suggestive of distant source input, and 3) effects of trophic status ( δ 15 N) and carbon source ( δ 13 C) on contaminant accumulation. Concentrations of Σ polychlorinated biphenyls (PCBs) and most chlorinated pesticides in glaucous-winged gulls consistently exhibited a ‘U’-shaped pattern of high levels at Buldir and the east side of Adak and low levels at Kiska and Amchitka. In contrast, concentrations of Σ PCBs and chlorinated pesticides in northern fulmars and tufted puffins did not differ among islands. Hg concentrations increased westward in glaucous-winged gulls and were highest in northern fulmars from Buldir. Among species collected only at Buldir, Hg was notably elevated in pelagic cormorants, and relatively high Σ PCBs were detected in black-legged kittiwakes. Concentrations of Σ PCBs, dichlorodiphenyldichloroethylene ( p , p ′ DDE), and Hg were positively correlated with δ 15 N across all seabird species, indicating biomagnification across trophic levels. The east side of Adak Island (a former military installation) was a likely point source of Σ PCBs and p , p ′ DDE, particularly in glaucous-winged gulls. In contrast, elevated levels of these contaminants and Hg, along with PCB congener and chlorinated pesticide compositional patterns detected at Buldir Island indicated exposure from distant sources influenced by a combination of atmospheric–oceanic processes and the migratory movements of seabirds.

Science of the Total Environment↗

USGS2002

Survival of Columbian white-tailed deer in western Oregon

Columbian white-tailed deer (Odocoileus virginianus leucurus; CWTD) are an endangered subspecies on which little demographic information exists. We determined survival rates and causes of mortality for 64 radiocol- lared adults from 1996 to 1998, and for 63 radiocollared neonatal fawns during the summer and fall months of 1996-2001 in Douglas County, Oregon, USA. Annual adult survival rates averaged 0.74 over 3 years, and most mor- tality (73%) occurred between fall and winter. Seasonal survival was lowest (0.75) for the fall-winter 1997-1998, and was 20.90 during all spring-summer periods. Annual and seasonal survival rates did not differ by gender. Average annual survival was 0.77 for deer in wildland areas compared with 0.66 for deer in suburban areas, but these dif- ferences were not consistent between years and seasons. Survival over the entire 3-year study was low (0.38). Eight deer died from a combination of emaciation and disease, and almost all (92%) necropsied deer were in poor body condition. Fawn survival to 7 months was low (0.14, 95% CI = 0.02-0.26) and declined most rapidly during the first 1.5 months of life. Predation (n = 21) and abandonment (n = 6) were the most frequent known causes of death for fawns. Our results suggest that CWTD may have responded to density-dependent factors during this short-term study, although the effects of other environmental or intrinsic factors cannot be ignored. Fawn survival may be insufficient to produce enough recruits for population growth and eventual range expansion.

Journal of Wildlife Management↗

USGS2001

Sexual segregation in Roosevelt Elk: Cropping rates and aggression in mixed sex groups

Few studies of sexual segregation in ruminants have tested widely invoked mechanisms of segregation in mixed-sex groups. In a sexually segregated population of Roosevelt elk ( Cervus elaphus roosevelti ), we examined if adult males had reduced intake of forage when in mixed-sex groups and if intersexual differences in aggression caused females to avoid males. Based on a mechanistic model of forage intake, animals with lower instantaneous feed intake should have higher cropping rates. Focal animal sampling indicated that adult males and females in summer and winter had similar cropping rates in mixed-sex groups, whereas males in male-only groups had lower rates of cropping than males in mixed-sex groups. Outside the mating season, males in male groups spent proportionally less time ≤1 body length of congenders than females in female groups, and the rate of aggression ≤1 body length was higher for males. Female–female aggression was higher in mixed-sex groups that contained more males than the median proportion of males in mixed-sex groups. Female and mixed-sex groups walked away when groups of males numbering >6 were ≤50 m but did not walk away when male groups ≤50 m had ≤5 individuals. Sexual segregation was associated with behaviors of sexes in mixed-sex groups: reduced intake of forage by males and increased female–female aggression with more males.

Journal of Mammalogy↗