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Assessing the Role of Marsh Habitat Change on the Distribution and Decline of Black Rails in Virginia
Wilson, M. D.
Wilson, M. D.
Abstract
The Black Rail is the most imperiled bird species within the Chesapeake Bay region and along the Atlantic Coast. Black Rail populations have been declining in the eastern United States for over a century resulting in a retraction of its breeding range, an overall reduction in the number of breeding locations within its core range, and a loss of individuals within historic strongholds. The Chesapeake Bay has historically supported the bulk of the Black Rail populations within the Mid-Atlantic region. However, systematic survey efforts in the Chesapeake Bay have shown that populations of the Black Rail have declined by more than 85 % in a relatively short time span of 15 years. Loss and transformation of habitat is often attributed as one reason for the dramatic decline of Black Rails. The Chesapeake Bay is undergoing a relatively high rate of sea-level rise that has been suspected of altering habitats in the past and expected to continue to do so into the future. The objective of this project was to investigate the potential of how physical changes observable through remote sensing may be influencing Black Rail habitat availability and eventually population status. We compared habitat use patterns and habitat use changes for systematic data and historical data on the distribution of Black Rails. We digitized marsh vegetation from 1994 and 2006 to compare the compositon of habitats thorugh a relatively important time frame that coincided with a steep decline of Black Rails in the Chesapeake Bay. Results suggest a consistent pattern for places where Black Rails have disappeared between 2007 and the early 1990s as being the same places that have undergone the most relevant changes in habitat composition. The best possible examples of the potential of habitat mediated population losses are found at Pig Point and Dix Hammock . Both of these marshes have experienced the greatest transformation of high marsh being replaced by low marsh. This exact type of habitat change that would be expected to result in a negative response by Black Rails. Physical changes in habitat as a consequence of sea-level rise are probably not the only reason contributing to population declines of Black Rails. Nest predation and increased inundation that drown nests may also be likely contributors.
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2014-01-01
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Wilson, M. D. 2014. Assessing the role of marsh habitat change on the distribution and decline of Black Rails in Virginia. Center for Conservation Biology Technical Report Series, CCBTR-14-09. College of William and Mary and Virginia Commonwealth University, Williamsburg, VA. 14 pp.