Tangier Islands Dialect

[David Bergdahl]

David L. Shores is the expert on the dialect--I would begin with his work:

David Shores' 1984 article, "The Stressed Vowels of the Speech of
Tangier Island, Virginia" in _Journal of English Linguistics_, Vol 17,
pp 37-56.
David L. Shores. Tangier Island: Place, People, and Talk. Cranbury, New Jersey: Associated University Presses.Hardbound $47.50 (0-87413-717-9). Tangier (pop. 700) is in Chesapeake Bay. Part 3 of this book describes the relic dialect of the island. 

See also Walt Wolfram's work on Ocracoke Island, a North Carolina Sea Island, which
also has a distinctive speech form.