Distribution, Relative Abundance and Status of the California Black Rail in Western North America

Abstract

We conducted breeding season surveys of California Black Rail (Laterallus jamaicensis coturniculus) populations in California and western Arizona from 1986-1989. During the course of our field work we developed a method to derive abundance indices and assign abundance values to each study area. We found the bulk of the population (> 80%) confined to the northern reaches of the San Francisco Bay estuary, especially the tidal marshland of San Pablo Bay and associated rivers. Elsewhere, distribution was patchy and subpopulations were small and isolated. Through a review of the literature, discussions with local field ornithologists, and our field work, we determined that the Black Rail population in Western North America is suffering a progressive decline. The causes of this downward trend-all related to habitat loss or degradation-are pervasive and ongoing.