The Negrito population that once resided along the Dicamay River to the west of Sierra Madre near Jones, Isabela spoke Agta, Dicamay [duy] (Headland, 2003). This Northern Cordilleran language was considered extinct (EGIDS 10) when its last speaker passed away in the 1960s (Headland, 2010 as cited in Eberhard et al., 2022).
On the language's extinction
Headland explains in two publications (2003; 2009) that in 1957, SIL linguist Richard Roe visited the only family that spoke the language and elicited a wordlist with 291 lexical terms. Headland came to Isabela in November 1974 to look for remaining speakers but was unsuccessful. He learned from residents of nearby areas that Ilocano settlers wiped out the Agta population several years ago, and the supposed Agta orphans were adopted by Ilocanos. However, when several cases of outsiders massacring Agta camp groups were recounted, there was no mention of the Agta, Dicamay speakers (Headland & Headland, 1999, as cited in Headland, 2003).
Works about Agta, Dicamay
The existing wordlists of Agta, Dicamay, one compiled by Richard Roe (1960) and the other collected by the Summer Institute of Linguistics (1957-1980), are classified and posted as drafts that have not yet undergone peer review. Both works are made available online to researchers and the language community.
Eberhard, D. M., Simons, G. F., & Fennig, C. D. (Eds.). (2022). Agta, Dicamay. Ethnologue: Languages of the World (25th ed.). https://www.ethnologue.com/language/duy
Headland, T. N. (2003). Thirty endangered languages in the Philippines. Work Papers of the Summer Institute of Linguistics, University of North Dakota Session, 47(1), 1-12. DOI: 10.31356/silwp.vol47.01
Headland, T. N. (2009). Why the Philippine Negrito languages are endangered. In M. Florey (Ed.), Endangered languages of Austronesia (pp. 110-118). Oxford Academic. https://doi.org/10.1093/acprof:oso/9780199544547.003.0006
Roe, G. R. (Comp.). (1960). Agta - Dicamay wordlist [Draft]. SIL International. https://www.sil.org/resources/archives/76818
SIL International. (1957-1980). Isabela wordlists [Draft]. https://www.sil.org/resources/archives/76709