Acoustical identification of Didunculus strigirostris, critically endangered Tooth-billed Pigeon of Samoa

The Tooth-billed Pigeon (Didunculus strigirostris) was classified as critically endangered in 2014. A Manumea Recovery Plan 2006–2016 was implemented by the Ministry of Natural Resources and Environment of Samoa (MNRE in Recovery plan for the Manumea or Tooth-billed Pigeon Didunculus strigirostris, Ministry of Natural Resources and Environment, Government of Samoa, Apia, 2006) but the main objectives of the plan could not be achieved because of the difficulty of discriminating between the coo calls of Didunculus strigirostris and those of the Pacific Imperial Pigeon (Ducula pacifia). The study provides key information for field work and training of a national team for monitoring Didunculus populations. The spectrographical and statistical analysis of coo calls of these two species shows significant differences in frequency traits. Calls of Didunculus are slightly higher than those of Ducula. The differences, however, are small and detectable only under optimal conditions. The coo calls show overlap in both pitch and length, so identification by call only in the field is not often possible; laboratory analysis of recordings is usually necessary.