Dataset Identification:
Resource Abstract:
- description: The federal and state endangered California clapper rail, Rallus longirostris obsoletus. is a species that, until
very recently, was on the verge of extinction. This secretive marsh bird's decline began over 100 years ago in the pristine
marshes of San Francisco Bay (Bay) and the California coast (Fig. 1). In the earlier part of this century, the rail was found
as far north as Humboldt Bay pd as far south as Morro Bay (Gill 1979) (Fig. 2). In the early 80s, the last known pair of rails
outside of the Bay was seen at Elkhorn Slough in Monterey County. During the first half of this century, exploitation of the
Bay's natural resources, including unrestricted filling and diking of the tidal marshes, began shrinking the rail's
habitat in San Pablo Bay, Central and South San Francisco Bay from over 51,000 hectares to less than 9,000 hectares that now
remain today (Dedrick 1993). The cumulative effects from this continued loss of critical habitat, combined with recent threats
from increased predation, probable contamination, and other stresses associated with expanding urban growth, has created a
crisis for our bay's indigenous rail. After the rail was listed as Endangered under the authority of the Endangered Species
Act by the U.S. Fish and Wildlife Service (Service) in 1970, censuses of the population in the Bay were initiated. In the
early 1970s, Gill estimated the total California clapper rail population at 4200 to 6000 individuals (1979). Surveys for the
rail continued into the 80s (Moss 1980), with Harvey providing an estimate of 1200-1500 rails in 1981. The survey by Harvey
was more accurate than the Gill estimate because an actual count was made, as compared to an average density which Gill applied
to all suitable habitat. Subsequent censuses were sporadic and incomplete (Harvey 1987) until the Service, led by the San
Francisco Bay National Wildlife Refuge (Refuge) began winter high tide surveys of South San Francisco Bay (South Bay) in 1988
(Foerster 1989). The Service began to suspect that the rail was in serious decline after the Refuge conducted a thorough survey
of major South Bay marshes in the winter of 1988-89 and estimated a total population of only 700 rails. It was discovered
that populations of rails in marshes on the east side of the bay were suffering the greatest declines and that predation by
non-native predators was implicated as a primary factor (Foerster 1989). This hypothesis was confirmed by data collected by
the Refuge and subsequently an Environmental Assessment and Predator Management Plan was implemented in March 1991 (Foerster
and Takekawa 1991). Since 1988, the Refuge has continued to conduct annual winter high tide surveys of South Bay rail populations
and some San Pablo Bay (North Bay) subpopulations (Figs. 2 and 3), with the assistance of the California Department of Fish
and Game (CDFG) and other local organizations such as the San Francisco Bay Bird Observatory. This report summarizes data
collected between November 1989 and January 1993, encompassing four annual winter surveys. During the last two years, the
Refuge also initiated research into several factors which were implicated in rail population decline. The factors which were
identified as significantly affecting rail survival included predation by non-native predators (Foerster and Takekawa 1991),
and high levels of heavy metals in prey species (Lonzarich, et al. 1992). Continued analysis of these factors by the Service
will culminate in a several reports to be released in late 1994.; abstract: The federal and state endangered California clapper
rail, Rallus longirostris obsoletus. is a species that, until very recently, was on the verge of extinction. This secretive
marsh bird's decline began over 100 years ago in the pristine marshes of San Francisco Bay (Bay) and the California coast
(Fig. 1). In the earlier part of this century, the rail was found as far north as Humboldt Bay pd as far south as Morro Bay
(Gill 1979) (Fig. 2). In the early 80s, the last known pair of rails outside of the Bay was seen at Elkhorn Slough in Monterey
County. During the first half of this century, exploitation of the Bay's natural resources, including unrestricted filling
and diking of the tidal marshes, began shrinking the rail's habitat in San Pablo Bay, Central and South San Francisco
Bay from over 51,000 hectares to less than 9,000 hectares that now remain today (Dedrick 1993). The cumulative effects from
this continued loss of critical habitat, combined with recent threats from increased predation, probable contamination, and
other stresses associated with expanding urban growth, has created a crisis for our bay's indigenous rail. After the
rail was listed as Endangered under the authority of the Endangered Species Act by the U.S. Fish and Wildlife Service (Service)
in 1970, censuses of the population in the Bay were initiated. In the early 1970s, Gill estimated the total California clapper
rail population at 4200 to 6000 individuals (1979). Surveys for the rail continued into the 80s (Moss 1980), with Harvey providing
an estimate of 1200-1500 rails in 1981. The survey by Harvey was more accurate than the Gill estimate because an actual count
was made, as compared to an average density which Gill applied to all suitable habitat. Subsequent censuses were sporadic
and incomplete (Harvey 1987) until the Service, led by the San Francisco Bay National Wildlife Refuge (Refuge) began winter
high tide surveys of South San Francisco Bay (South Bay) in 1988 (Foerster 1989). The Service began to suspect that the rail
was in serious decline after the Refuge conducted a thorough survey of major South Bay marshes in the winter of 1988-89 and
estimated a total population of only 700 rails. It was discovered that populations of rails in marshes on the east side of
the bay were suffering the greatest declines and that predation by non-native predators was implicated as a primary factor
(Foerster 1989). This hypothesis was confirmed by data collected by the Refuge and subsequently an Environmental Assessment
and Predator Management Plan was implemented in March 1991 (Foerster and Takekawa 1991). Since 1988, the Refuge has continued
to conduct annual winter high tide surveys of South Bay rail populations and some San Pablo Bay (North Bay) subpopulations
(Figs. 2 and 3), with the assistance of the California Department of Fish and Game (CDFG) and other local organizations such
as the San Francisco Bay Bird Observatory. This report summarizes data collected between November 1989 and January 1993, encompassing
four annual winter surveys. During the last two years, the Refuge also initiated research into several factors which were
implicated in rail population decline. The factors which were identified as significantly affecting rail survival included
predation by non-native predators (Foerster and Takekawa 1991), and high levels of heavy metals in prey species (Lonzarich,
et al. 1992). Continued analysis of these factors by the Service will culminate in a several reports to be released in late
1994.
Citation
- Title Summary of California Clapper Rail Winter Populations in the San Francisco Bay, 1989 to 1993.
-
- creation Date
2018-05-21T07:34:07.783322
Resource language:
Processing environment:
Back to top:
Metadata data stamp:
2018-08-06T21:54:26Z
Resource Maintenance Information
- maintenance or update frequency:
- notes: This metadata record was generated by an xslt transformation from a dc metadata record; Transform by Stephen M. Richard, based
on a transform by Damian Ulbricht. Run on 2018-08-06T21:54:26Z
Metadata contact
-
pointOfContact
- organisation Name
CINERGI Metadata catalog
-
- Contact information
-
-
- Address
-
- electronic Mail Address cinergi@sdsc.edu
Metadata language
eng
Metadata character set encoding:
utf8
Metadata standard for this record:
ISO 19139 Geographic Information - Metadata - Implementation Specification
standard version:
2007
Metadata record identifier:
urn:dciso:metadataabout:857e8494-c20f-47f5-83e4-25955ba982cc
Metadata record format is ISO19139 XML (MD_Metadata)