Assessment of Black Rail Status in Georgia, Breeding Season 2017 and 2018 Summaries
Abstract
The Black Rail (Laterallus jamaicensis) is the most secretive and least understood marsh bird in North America with the Eastern Black Rail (L. j. jamaicensis), one of two subspecies that occur here, listed as endangered in six states along the Atlantic Coast and proposed for federal listing under the Endangered Species Act (USFWS–R4–ES–2018–0057, 2018). Black Rails require dense vegetation for cover during all stages of their life cycle. They require wetlands with minimal water coverage during the breeding season. Historic population size for the Eastern subspecies was likely in the tens of thousands (25,000 to 100,000; Delaney and Scott 2002) but is now believed to be in the hundreds to low thousands. Eastern Black Rails breed within three geographic areas within North America including the Atlantic Coast, the Gulf Coast, and the Midwest. The Atlantic Coast has generally been considered to support the largest breeding population throughout the range with pairs mostly confined to the highest elevations within tidal salt marshes. Breeding range along the Atlantic Coast has contracted south more than 450 kilometers and the population is estimated to be declining by 9% annually (Watts 2016). The primary driver of declines over the past three decades is believed to be sea-level rise and associated tidal inundation during the nesting season. Georgia is noticeably missing from most of the early descriptions of Eastern Black Rail distribution (e.g. Allen 1900, Bent 1926, Forbush 1929). Early authors describing Eastern Black Rail status in the state (Burleigh 1938, Greene et al. 1945, Burleigh 1958) indicate that the species was perhaps more common and widespread in previous decades. As in all states within the breeding range, the lack of status and distribution information is certainly facilitated by their secretive habits, but in Georgia this is also likely reflected in an extremely low population size, a lack of overlap between Black Rails and bird watchers, or both. Scattered historic occurrences along the outer coast suggested a presence of a potential breeding population (Sykes 2010). The Eastern Black Rail ranks as a species of high conservation concern (GA DNR Wildlife Action Plan 2015) and breeding season surveys ranked as one of the highest conservation action priorities within the plan. The 2016 population estimate for the state (based on available habitat) was 10 to 40 pairs though the uncertainty in this estimate was very high (Watts 2016). The only definitive breeding record in the state comes from Greene County (Sykes 2010), and this site has been the most consistently documented breeding area throughout the state in the past 25 years (Watts 2016). During the 2017 field season, 409 coastal points were surveyed, and during the 2018 field season 206 points were surveyed. All points surveyed in 2017 were along the outer coast in tidal or impounded wetlands. During the 2018 survey, 141 inland points and 65 coastal points were surveyed. Three rounds of surveys were conducted between 18 April and 17 July 2017 and between 1 May and 15 July 2018. All points were surveyed three times unless there were access issues during one of the survey rounds. A total of 1,827 individual play-back surveys were conducted, 1,213 in 2017, and 614 in 2018. We detected no Black Rails during either season.
