The Black Rail: A New Resident of Oak Ecosystems
Oak woodlands provide habitat for California's most diverse array of terrestrial wildlife. At least 331 vertebrate species utilize these habitats, including 160 species of birds. We can now expand this list with the addition of a very unexpected discovery. The California black rail (Laterallus jamaicensis coturniculus), a secretive, tiny, short-legged marsh bird, has recently been reported as a year-round resident of wetlands on hardwood rangelands. This is unusual for a bird that normally lives in coastal tidal and delta marshes, where dwindling populations have caused it to be listed as a threatened species by the State of California and as a candidate for endangered status by the federal government. No one had thought to look for it in the foothills. Audubon Field Notes describe this occurrence as "mind bending."
Researchers accidentally discovered probable breeding populations in a small, densely vegetated strip of marsh along a spring-fed watercourse, and in stream overflow areas and irrigation seepage at the Sierra Foothill Research and Extension Center (SFREC) near Browns Valley in Yuba County. Subsequent search has so far turned up a dozen populations in the SFREC vicinity, as well as in Butte and Nevada counties. The birds seem to require dense cattail, rushes, or sedge vegetation in well-drained settings, with perennial water flow and water levels an inch deep or less. Foothill springs, or even irrigation ditch leaks, that maintain marshes or wet meadows as small as one acre, even if surrounded by dry annual grassland or woodland, could be black rail habitat. Some rails have been found in wetlands that have originated in recent decades, so they appear to invade newly created habitats. They are likely to be found in marginal use areas, where vegetation is not especially desirable or extensive for grazing and too wet for other uses. Some areas moderately winter-grazed by cattle have even been found to continue to attract black rails. Proximity to heavily traveled roadways and home sites does not seem to limit their occurrence.
The California black rail is the smallest North American rail, the size of a small sparrow. It short legs confine it to shallow water. It is more gray than black, with a chestnut mantle and white speckles on the back. Adults have unusual flaming red eyes. However, don't count on seeing it, for it is one of our mot elusive birds. It seldom is seen in flight (probably only flies at night), stays deep within dense cover, and scurries rapidly across openings. I've been with an experienced birder who saw one dash between sedge tussocks, and thought it was a mouse. It can, however, readily be identified by its distinctive call, a three note piping sound that seems to say "kee-kee-do". Under the right circumstances, a marsh can come alive with territorial males counter-calling or chorusing this call for lengthy periods. When highly disturbed, it also has a distinctive growl-like vocalization that greatly exaggerates its tiny source. Information about its life cycle and habits is sketchy or non-existent.
Black rails have been reported in a few other inland, fresh-water locations in marshes along the lower Colorado River in California and Arizona. These populations, like those of the oak woodland, appear to be resident rather than migratory. This raises the question of whether they represent a persistent remnant of an earlier, more widespread distribution, from times when marshlands were more extensive and connected; or if they are more recent arrivals, newly dispersed in a chance manner to a few inland locations. At this time we do not know the extent of the inland distribution of the black rail or how they got here. Nor do we know how these populations relate to those of the coastal marshes.
California black rails are probably more numerous than has previously thought. This is encouraging news for a threatened species whose coastal habitat is under intense development pressure. It is also encouraging to find them in small, marginal foothill settings, which can probably be easily protected and preserved. An understanding of how these mini-marshlands of the oak woodland are satisfying the biological requirements of the black rail would contribute greatly to drafting a recovery plan for the species.
Aigner, Paul A.; Jerry Tecklin; and Catherine E. Koehler. 1995. Probable breeding population of the black rail in Yuba County, California. Western Birds 26:157-160.