Light-footed Clapper Rail Research Articles

Inorganic Analytes in Light-Footed Clapper Rail Eggs, in Their Primary Prey, and in Sediment From Two California Salt Marsh Habitats

Inorganic Analytes in Light-Footed Clapper Rail Eggs, in Their Primary Prey, and in Sediment From Two California Salt Marsh Habitats

Site Conditions, Not Parental Phenotype, Determine the Height of Spartina foliosa

The effect of parental growth form on ramets introduced to new sites has broad implications for ecological restoration. We asked whether transplants ofSpartina foliosa need to come from tall parents in order to produce tall stands for nesting by the light-footed clapper rail, one of southern California’s many endangered, salt-marsh-dependent species. Tall and shortS. foliosa transplants, collected from local salt marshes, were grown in a common garden and in microcosms, with different results. In the common garden, which had hypersaline soil, offspring of tall versus short clones did not differ, but they did respond to soil variations among blocks. In blocks with less sandy soil, stems were taller and up to 5 times more numerous, and patch sizes were up to 3 times larger. After two years in low-salinity microcosms, transplants receiving nitrogen additions produced more stems and over twice the total stem length of controls, regardless of parental height form. A slight parental effect was seen in this benign environment; the maximum height of tall-form transplants was 15 cm taller than that of short-form transplants, but the effect did not persist through year 2. Results indicate that both height forms ofS. foliosa grew better (taller and more dense) with less environmental stress (lower salinity, more nutrients). We conclude that environmental differences are more important than parental height form in determiningS. foliosa growth. This means that, for restoration purposes,S. foliosa ramets can and should be collected from short clones, rather than from existing, prime nesting habitat.

EFFECTS OF NITROGEN ADDITIONS ON THE VERTICAL STRUCTURE OF A CONSTRUCTED CORDGRASS MARSH

Because tall vegetation can enhance habitat quality in intertidal wetlands, we examined the effects of N fertilization on the height growth of a constructed cordgrass (Spartina foliosa) marsh in San Diego Bay, where plants are short and soil N low. We varied the duration (therefore also the quantity; 30 g N/m2 every month for 1, 2, 4, or 6 mo) and timing (30 g N/m2 in March, April, June, or August) of N additions during 1993. By fertilizing a second set of replicates for the 6-mo treatment during 1994, we were able to examine the persistence of effects from 1993 vs. the effects of amendments in both years. Traditional canopy response measures (total stem length, maximum height, foliar N) increased most with the greatest duration/quantity of additions in 1993. All duration and timing treatments produced canopies with >100 stems/m2 and ≥30 stems/m2 taller than 90 cm, considered suitable for nesting by the endangered Light-footed Clapper Rail (Rallus longirostris levipes). However, without additional fertilizer in 1994, the previous year’s canopy responses were not retained, suggesting insufficient storage of N in belowground tissues. Only plots fertilized in both years continued to produce ≥30 tall stems/m2. The coarse dredge-spoil sediments of the constructed marsh had only 1/4 to 1/3 the total N found in the fine-textured soils of a nearby natural marsh, where cordgrass grows tall and clapper rails nest. We recommend that future marsh restoration projects begin with fine soils that promote N retention and accumulation to sustain tall canopies, rather than suggesting long-term fertilization.

Food web analysis of southern California coastal wetlands using multiple stable isotopes.

Carbon, nitrogen, and sulfur stable isotopes were used to characterize the food webs (i.e., sources of carbon and trophic status of consumers) in Tijuana Estuary and San Dieguito Lagoon. Producer groups were most clearly differentiated by carbon, then by sulfur, and least clearly by nitrogen isotope measurements. Consumer 15N isotopic enrichment suggested that there are four trophic levels in the Tijuana Estuary food web and three in San Dieguito Lagoon. A significant difference in multiple isotope ratio distributions of fishes between wetlands suggested that the food web of San Dieguito Lagoon is less complex than that of Tijuana Estuary. Associations among sources and consumers indicated that inputs from intertidal macroalgae, marsh microalgae, and Spartina foliosa provide the organic matter that supports invertebrates, fishes, and the light-footed clapper rail (Rallus longirostris levipes). These three producers occupy tidal channels, low salt marsh, and mid salt marsh habitats. The only consumer sampled that appears dependent upon primary productivity from high salt marsh habitat is the sora (Porzana carolina). Two- and three-source mixing models identified Spartina as the major organic matter source for fishes, and macroalgae for invertebrates and the light-footed clapper rail in Tijuana Estuary. In San Dieguito Lagoon, a system lacking Spartina, inputs of macroalgae and microalgae support fishes. Salicornia virginica, S. subterminalis, Monanthochloe littoralis, sewage- derived organic matter, and suspended particulate organic matter were deductively excluded as dominant, direct influences on the food web. The demonstration of a salt marsh-channel linkage in these systems affirms that these habitats should be managed as a single ecosystem and that the restoration of intertidal marshes for endangered birds and other biota is compatible with enhancement of coastal fish populations; heretofore, these have been considered to be competing objectives.

RAPD analysis reveals low genetic variability in the endangered light‐footed clapper rail

Numbers of light-footed clapper rails Rallus longirostris levipes, an endangered bird inhabiting southern California salt marshes, have substantially declined from historic levels. RAPD (randomly amplified polymorphic DNA) analysis was employed to assess the genetic variability within and among four of the largest remaining light-footed clapper rail populations. A single, larger population of the endangered Yuma clapper rail Rallus longirostris yumanensis was used for comparison. A total of 325 RAPD primers were tested on DNA from a subset of five clapper rails composed of a single representative for each of the four light-footed clapper rail populations and a representative for the single Yuma clapper rail population. Of the 1338 amplified bands (loci) surveyed in these five representative birds, approximately 1% were polymorphic, indicating the level of differentiation across all loci is quite low. Nine primers yielding these 16 polymorphic bands were used to analyse 48 individuals from five populations. Five of these bands were polymorphic in both subspecies, six were polymorphic only within the light-footed clapper rails, and five were polymorphic only within the Yuma clapper rail samples. Considering the few bands that were polymorphic among the light-footed clapper rail populations, a surprisingly high level of population differentiation (GST = 0.28) was found. This is in accord with the results of AMOVA analyses which show that a fairly high percentage of the limited variability among the rails is due to either differences between subspecies or differences between the light-footed rail populations. Because inbreeding depression is suspected and overall genetic distances between populations are low, movement of light-footed clapper rails from larger populations into smaller ones might be considered as a management strategy. Employing RAPDs as one of a series of assays is useful in revealing the population structure of genetically depauperate species.

Influence of physical processes on the design, functioning and evolution of restored tidal wetlands in California (USA)

The performance of two intertidal wetland mitigation projects constructed by the California Department of Transportation (Caltrans) in the Sweetwater Marsh National Wildlife Refuge (SMNWR) in San Diego Bay was evaluated over 5 years. Most of the Sweetwater wetland complex has been altered this century, including diking (with subsequent subsidence), filling, modification of the tidal regime, freshwater inflow and sediment fluxes. The mitigation project goals included a range of functional criteria intended to support two endangered bird species (light-footed clapper rail and California least tern) and one endangered plant (salt marsh bird's-beak). While the mitigation projects have achieved some of the performance criteria established in the regulatory permits (particularly, those related to fish), vegetation criteria for one of the bird species have not been met. The initial grading (in relation to local tidal datums) should support the target plant species, but growth has been less than required. Shortcomings of the habitat include elevated soil and groundwater salinity, low nutrient levels (especially nitrogen, which is readily leached from the coarse substrate), and eroding topography (where a single oversized and overly sinous channel and the lower-than-natural marshpalin result in high velocity surface water flow and erosion). The failure to achieve a large plain at low-marsh elevations highlights the importance of a more complete understanding of the relationship between the site physical processes (topography, hydrology, climate, geomorphology), substrate conditions, and biotic responses.

Simulation model evaluation of potential recovery of endangered light-footed clapper rail populations

Conservation of the endangered light-footed clapper rail Rallus longirosris levipes is a major objective in the remaining areas of Southern California salt marsh. We used simulation modeling to determine the potential of different types of estuaries and different management strategies for increasing the size of the rail population. Analyses of existing data show that the size of breeding populations of rails is closely associated with above-ground biomass of Pacific cordgrass Spartina foliosa. A model cordgrass was constructed to analyze the effects of salinity and soil moisture, and of the impact of various management actions, on the potential for biomass production. The model shows that keeping the salt marsh open to the sea is critically important, but that enhancing the fresh water supplied to the marsh has mixed results. The simulation model was used in conjunction with field estimates of rail density to estimate the potential for rail population recovery. These estimates show that full implementation of the recovery plan for rails is only possible if all remaining wetland area is restored to high-quality rail habitat. Our results suggest that a greater benefit to rails may result from concentrating on habitat improvement of those estuaries that have the greatest potential for Spartina production rather than the dispersion of expenditures upon all existing wetlands, many of which may have limited potential for rail population expansion.

Movements and Activity Patterns of the Light-Footed Clapper Rail

We monitored 54 individually color-banded light-footed clapper rails (Rallus longirostris levipes) (9 were harnessed for radio telemetry) to determine movements, home range, and activity patterns. Resightings over 3 years indicated a strong site tenacity. Maximum distances between locations for a given rail were generally 95%) was done during daylight hours. To check for nighttime activity, fixes were taken on 4 rails every 2-3 hours through 1 night each. Of our total tracking effort, 37% of locations were obtained in the first 4 hours of daylight, followed by 19, 26.9, and 16.5%, respectively, in consecutive 4-hour time blocks. Position fixes were taken every 15-30 minutes. Rails under visual observation yielded more fixes/unit of time, whereas rails roosting through high tides did not change position and, therefore, were not checked as often. Tracking stations were situated along the edge of the marsh, 15-50 m apart. The telemetered rails were within 50 m of the observer. The presence of an observer did not appear to affect a rail's behavior because rails were habituated to human activity (e.g., biking, jogging, class tours, boating, driving, and picnicing). Two or more readings were taken within 515 minutes, to determine a single location for a telemetered rail by triangulation. The data were entered into a computer that converted our compass readings to Cartesian coordinates. The program discarded fixes with >3 readings that crossed >5 m apart. A graphics plotter displayed the spread of fixes for a rail on maps of approximately 1:1,719-1:4,132 scale. Movements and range were measured on these maps with a digital planimeter and calipers. Home ranges were calculated using minimum convex polygons. We assessed activity patterns based on visual observations of the 4 most frequently observed telemetered rails and the mate of 1 of them. We quantified vocalizations by counting each bout of calling by each rail as 1 vocalization. We sexed rails by observing the behavior of m ted pairs. Also, the females of mated pairs were always smaller than the males. This size difference was corroborated by the measurement of 100 museum skins, measurements of 12 rails subsequently observed mating, and measurements of 5 birds later found dead and examined by laparotomy. Birds referred to by sex, herein, are only those observed mating or later dissected.

Foraging Behavior and Foods of the Light-Footed Clapper Rail

Journal Article Foraging Behavior and Foods of the Light-Footed Clapper Rail Get access Richard Zembal, Richard Zembal U.S. Fish and Wildlife Service, 24000 Avila Road, Laguna Niguel, CA 92656 Search for other works by this author on: Oxford Academic Google Scholar Jack M. Fancher Jack M. Fancher U.S. Fish and Wildlife Service, 24000 Avila Road, Laguna Niguel, CA 92656 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 90, Issue 4, 1 November 1988, Pages 959–962, https://doi.org/10.2307/1368864 Published: 01 November 1988 Article history Received: 18 April 1988 Accepted: 07 July 1988 Published: 01 November 1988