Jeffrey Mackay | Geology Reports

USGS2003

Long term productivity of canvasbacks ( Aythya valisineria ) in a snowpack-driven desert marsh

Ruby Lake, Nevada, is a large palustrine wetland that hosts the southern-most major breeding population of Canvasbacks ( Aythya valisineria ). That arid marsh, fed by springs derived from mountain snowpack, differs in climate and hydrology from glaciated potholes of the northern prairies where most Canvasbacks breed. Fourteen years of nesting data on Canvasbacks over a 31 year period (1970–2000) were analyzed to determine factors affecting breeding performance at Ruby Lake and whether they differed from those in the prairies. Long-term Mayfield nest success at Ruby Lake (50% of all nests) was in the range of that in the northern prairies (21–65%). Of all Canvasback nests, 73% were parasitized (mostly by Redheads [ Aythya americana ]) as compared to 83–97% in a large Manitoba marsh and 57–65% in Manitoba potholes. However, as in the northern prairies, nest parasitism generally had little or no effect on either nest success or percentage of host eggs that hatched. In Manitoba potholes, nest success was unrelated to habitat variables measured; but successful nests at Ruby Lake were over shallower water, farther from shore, in wider bands of emergent vegetation, and surrounded by lower stem densities than unsuccessful nests. Water level is the key factor in breeding performance of Canvasbacks at both Ruby Lake and the northern prairies; however, the source of water differs (mountain snowpack at Ruby Lake, direct precipitation in the prairies) and effects of water-level variations are reversed. In small prairie potholes (mostly <0.4 ha) with many mammalian predators, productivity of Canvasbacks (which build floating nests) is increased by high water that floods the emergent fringe. At Ruby Lake, a very large marsh (2,830 ha) with mostly avian predators, Canvasback productivity is decreased by high water that floods interior emergent stands too deeply. Water level at Ruby Lake was highly correlated (multiple R 2 = 0.91) with mountain snowpack up to three years earlier, emphasizing the strong effect of climatic variations on wetland birds in that arid region.

The Auk↗

USGS2001

Estimates of evapotranspiration from the Ruby Lake National Wildlife Refuge area, Ruby Valley, northeastern Nevada, May 1999–October 2000

The Ruby Lake National Wildlife Refuge in Ruby Valley, Nevada, contains the largest area of perennial wetlands in northeastern Nevada and provides habitat to a large number of migratory and nesting waterfowl. The long-term preservation of the refuge depends on the availability of sufficient water to maintain optimal habitat conditions. In the Ruby Valley water budget, evapotranspiration (ET) from the refuge is one of the largest components of natural outflow. To help determine the amount of inflow needed to maintain wetland habitat, estimates of ET for May 1999 through October 2000 were made at major habitats throughout the refuge. The Bowen-ratio method was used to estimate daily ET at four sites: over open water, in a moderate-to-dense cover of bulrush marsh, in a moderate cover of mixed phreatophytic shrubs, and in a desert-shrub upland. The eddy-correlation method was used to estimate daily ET for periods of 2 to 12 weeks at a meadow site and at four sites in a sparse-to-moderate cover of phreatophytic shrubs. Daily ET rates ranged from less than 0.010 inch per day at all of the sites to a maximum of 0.464 inch per day at the open-water site. Average daily ET rates estimated for open water and a bulrush marsh were about four to five times greater than in areas of mixed phreatophytic shrubs, where the depth to ground water is less than 5 feet. Based on the seasonal distribution of major habitats in the refuge and on winter and summer ET rates, an estimated total of about 89,000 acre-feet of water was consumed by ET during October 1999-September 2000 (2000 water year). Of this total, about 49,800 acre-feet was consumed by ET in areas of open water and bulrush marsh.

Nevada↗