We do not guarantee individual replies due to extremely high volume of correspondence. Throughout the Bay, the remaining clapper rail population is besieged by mammal and bird predators. Present-day tidal-marsh habitat in San Francisco Bay is ∼15% of historical (1850s) acreage (Dedrick 1989). Mercury concentrations were determined by cold-vapor atomic absorption using a PerkinElmer model 403 AA (PerkinElmer, Boston, Massachusetts). San Francisco Bay National Wildlife Refuge, Newark, California. The data were not normal (Shapiro-Wilk test, P = 0.0338). Only 69% of eggs whose viability could be assessed were viable. Higher mean concentrations of aluminum, barium, chromium, and strontium were statistically associated with the presence of deformities in the North Bay eggs, whereas mean concentrations of lead, boron, and mercury were not. All these contaminant-induced adverse effects would give an advantage in the wild to potential predators of California Clapper Rails. People Interactions Though their chattering call is often heard, rails are not often seen except by avid bird-watchers or hunters. 1980). Other South Bay marshes were assessed only in 1992. Barium concentrations were significantly higher in late-stage eggs and were highest in the three embryos with deformities of the feet. Most boron concentrations in eggs, however, were below known avian embryotoxic thresholds (Smith and Anders 1989). A clattering cackle in the salt marsh is often our first clue to the presence of this big rail. Johnson (1973) observed a hatchability rate of 92.3% in Northern Clapper Rails in 98 nests in Nassau County, New York, in the late 1960s. Selenium concentrations in the deformed embryos were the lowest among all embryos observed in the present study. The only breeding population of this subspecies is now located solely in the intertidal margins of San Francisco Bay. Typically birds ride out storms by moving to higher areas of the marsh. You might not need every rivet in place for the airplane to fly, but would you fly it through a cyclone if you knew that 10% of its rivets were missing? No significant differences were found (P = 0.3904). Rails can move upstream along riparian corridors from breeding habitat to freshwater marsh habitat S. N. Q., and Methylmercury concentration in eggs was strongly correlated with total mercury concentrations (r2 = 0.81, P < 0.000001). Concentrations of PCBs were high enough to exert an effect on hatch-ability in only one California Clapper Rail egg from the South Bay (Laumeister Marsh) in 1992 (Schwarzbach et al. S. N.Wiemeyer, and South San Francisco Bay breeding bird survey, 1971. Nesting habitat of the Light-footed Clapper Rail in southern California. In the North Bay in 1998-1999, we observed that 52.3% of eggs in Corte Madera Marsh were eaten by predators; whereas at Wildcat Marsh, only 12.9% of the eggs were lost to predation. But we believe that preserving marshes instead of weakening them can improve the chance of a smooth landing. 2002). University of California, Berkeley, Richmond Field Station There are sharp-pointed plants, such as black needlerush, and sucking mud. The head was either not correctly placed at the air-cell pole of the egg or was not correctly tucked beneath the right wing. Organochlorine concentrations in eggs are presented as the FWW value. Sólo el 69% de los huevos cuya viabilidad pudo ser determinada fueron viables. California Clapper Rail nest success was evaluated in six intertidal salt marshes in San Francisco Bay, California. One of these embryos was polydactylus, with an extra digit on each foot and edema in the neck region. The Clapper Rail is usually hidden in dense cover, but sometimes we see it stalking boldly along the muddy edge of the marsh, twitching its short tail as it walks, or swimming across a tidal creek. Only one egg, from Wildcat Marsh, had an elevated boron concentration. Concentrations of all organochlorines in eggs were greater at Corte Madera than at Wildcat. Through this process we've been able to estimate the distributions of several species in tidal marshes, including clapper rails, least bitterns (Ixobrychus exilis) and seaside sparrows (Ammospiza maritima). Las inundaciones fueron un factor poco importante, pues redujeron el número de huevos disponibles para eclosionar sólo en un 2.3%. Lonzarich, Egg hatchability in North Bay and South Bay marshes was 65% and 70%, respectively. Some of the urban predators that disturb or kill sensitive bird species in our county include crows, ravens, raccoons, opossums, rats — and feral cats. Concentrations in eggs in the North Bay also appear to have declined by ∼50% since the mid-1980s (Table 3), when selenium was elevated in Wildcat Marsh in particular. The others include the sora, Virginia, king, black and yellow rail. Even with this variety of rail species, the clapper rail is likely only to be confused with the king rail, a slightly larger bird that prefers freshwater marshes. This assessment, conducted in four breeding seasons (1991, 1992, 1998, 1999), determined that productivity of California Clapper Rails was much reduced over the natural potential. Concentrations in North Bay failed eggs, however, were half those found in the mid-1980s. You can be assured our editors closely monitor every feedback sent and will take appropriate actions. The detection limit for barium in 1992 eggs was 0.1 μg g−1. San Francisco Bay tidal marshland acreages: Recent and historic values. thesis, Stanford University, Palo Alto, California. We are currently studying how marsh birds such as clapper rails (Rallus crepitans) have adapted to tropical storms along the Alabama and Mississippi Gulf coast. Other trace-element analytes were determined by a Jarrell-Ash model 1100 Mark III, after a preconcentration step and nitric-perchloric digestion. In the South Bay, Laumeister had the most severe predation, with 61% of all eggs laid taken by predators. Mean (± SE) percentage of moisture in eggs was 75.6 ± 0.4%). The detection limit for lead in 1992 eggs was 1 μg g−1 DW. To assess whether a significant fraction of mercury in California Clapper Rail eggs was not in the methylmercury form, methylmercury concentration was determined for a subset of nine North Bay and eight South Bay eggs.
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