|A Farallon arboreal salamander. Photo by Derek Lee/PRBO.|
A surprising number of arboreal salamanders inhabit Southeast Farallon Island, living deep in crevices during the dry season but dwelling near the surface when conditions are moist. PRBO has recently provided U.S. Fish and Wildlife Service (USFWS) with the first scientific assessment of the amphibian’s status on the island. A 2010 report on the first three years of this study considers the arboreal salamander as a valued and sensitive Farallon species.
The study method involved placement of about 100 mid-sized boards on the ground and, from November through April, regularly checking underneath them to count and measure the salamanders gathered there. Though the Farallon population size is not known, PRBO biologists in three years did record more than 1800 salamander encounters and marked more than 500 individuals.
Amphibians are “thin-skinned” and very vulnerable to environmental factors such as toxins, disturbance, and climate-related stresses. The arboreal salamander is long-lived and slow to mature, making adult survival rates particularly crucial. This same life-history factor is important in the management of other sensitive Farallon species, such as the Cassin’s Auklet.
PRBO’s salamander report for USFWS concludes: “This is a special, insular population and is the only native terrestrial vertebrate of the Farallones whose individuals and habitat need protection similar to other island fauna.”
|Golden-crowned Sparrow. Photo by Tom Grey.|
In an impressive show of homing ability, several Golden-crowned Sparrows returned in fall 2010 to the same locations where PRBO biologists had banded them eight months earlier.
The sparrows had completed a full migration cycle to their northerly nesting grounds and back to coastal Marin County for the winter. Twelve of the 33 Golden-crowns that were banded and/or carried tiny geolocator tags on this journey (see Observer 160, spring 2010) chose precisely the same wintering grounds as last year.
Because of songbirds’ remarkable site fidelity, PRBO researchers were able to recover four tags, with the hope of also recovering data about the birds’ travel patterns. Stay tuned!
Meanwhile, a sampling of Swainson’s Thrushes that nest near PRBO’s Palomarin Field Station are also wearing geolocator tags. They are now in Latin America for the winter. Some may return to our study area this spring. Neotropical migrants returning to their breeding grounds also exhibit strong site fidelity, as shown in PRBO’s long-term monitoring research.
With new micro-technology, we are trying to address the lack of knowledge about the birds’ conservation needs throughout their year-long cycles.
Dunlin—in new shorebird surveys.
|Dunlin. Photo by Tom Grey.|
In 2010 PRBO launched the new Pacific Flyway Shorebird Survey, and data gathered in the first year indicate that Dunlin is the most numerous shorebird species wintering in California.
This large-scale survey effort is a continuation of the Pacific Flyway Project, coordinated by PRBO from 1988 to 1995. It established the first baseline of data on shorebirds migrating between Alaska and Baja California.
Many shorebird species are likely declining in North America, and large-scale changes affect wetland habitats in California. PRBO designed new surveys to increase knowledge about which species and habitats are at greatest risk. In 2010, we trained 54 citizen scientists and established several hundred survey points in the Sacramento Valley and around San Francisco Bay.
While documenting shorebirds across these regions in November and December 2010, surveyers were greeted with the spectacle of large Dunlin flocks, both on tidal estuaries and in flooded rice fields.