Conservation Biology of the Critically Endangered Bahama Oriole: Estimating Current Population Size and Evaluating Threats

Abstract

The Bahamas and adjacent Caribbean islands are home to eight island endemic orioles, half of which are Threatened or Near Threatened. The Bahama Oriole (Icterus northropi) is listed by IUCN as Critically Endangered. This species is currently restricted to Andros Island, as it was extirpated from Abaco Island during the 1990s due to unknown causes. The only formal study of this species was a PhD thesis, which estimated that only 141-254 individuals remained (Price et al., J. Field Ornithology, 2011). First, we will estimate the current population size using distance sampling to obtain census estimates with statistically robust confidence intervals. We will conduct both breeding season and non-breeding season counts to determine which habitats are crucial to the species during the whole annual cycle. Second, we will monitor breeding success and evaluate known threats including cowbirds, native nest predators, introduced feral predators and lethal yellowing disease of palm trees. Third we are using remote sensing and ground truthing to map five major habitat types. A pilot field trip in May 2016 documented three pairs nesting deep within pine forest for the first time. Although densities may be low in pine forests, since the majority of terrestrial habitat is pine, this habitat could be crucial to the species. The Bahamas National Trust (BNT) and the University of Maryland (UMBC) are leading this collaborative effort, with the support of Audubon and the American Bird Conservancy. We are seeking additional funding to enable a comprehensive long-term approach to ensuring the survival of the Bahama Oriole.