Data Zone
Justification of Red List category
Despite being larger than previously assumed, the population size of this species is very small and undergoing a continuing decline due to the impacts of predation by invasive species and nest parasitism. Moreover, the population is at risk of hurricanes and sea-level rise, which may cause the flooding and destruction of key pine forest habitat. The species is therefore listed as Endangered.
Population justification
Point count surveys following a distance sampling design in northern North Andros estimated a population of c. 1,200-2,800 mature individuals in the study area (Rowley et al. 2021). The study site included the largest area of pine forest on Andros, which was found to be the species’ preferred habitat (Rowley et al. 2021). These forests may represent around 30-50% of good pine forest habitat present on Andros and may hold a large proportion of the global population, as other pine forests are small, patchy and likely not used as much by the species (J. Antalffy and K. Omland pers. comm. 2021). Tentatively, it is assumed that global population is 2-3 times higher than the estimate for the study site in North Andros (J. Antalffy and K. Omland pers. comm. 2021) and is therefore here placed in the band 2,400-8,400 mature individuals.
The species has been extirpated from Abaco and now only occurs on Andros. Its ability to use a variety of habitats suggests that all individuals may get in contact with each other, and it is therefore assumed that the species forms a single subpopulation.
Trend justification
The species is thought to undergo a continuing decline due to the combined effects of predation by invasive species, nest parasitism by Shiny Cowbirds and the loss and degradation of its preferred pine forest habitat through the impacts of hurricanes and subsequent saltwater inundations, as well as through clearance for agriculture.
The rate of decline has not been quantified, but it is considered unlikely to exceeded 30% over the past three generations (10.3 years; Bird et al. 2020). The rate of decline may however increase rapidly in the future, as the species and its habitat are at high risk of hurricanes and storm-surge flooding. The intensity, and probably the frequency of hurricanes in the Atlantic are projected to increase with climate change (see e.g., Knutson et al. 2010; Walsh et al. 2016; Hall and Kossin 2019). While pine forests show resilience to storms, they are very sensitive to flooding and saltwater inundation and may take decades to recover (B. Watson pers. comm. 2021). Potentially severe storms and flooding on Andros in the near future may prove detrimental for the species and its habitat and increase the rate of decline considerably.
Icterus northropi is endemic to the Andros group in The Bahamas, including North Andros, South Andros and Mangrove Cay. It formerly occurred on Abaco, but it became extirpated in the early 1990s (M. Price in litt. 2010, 2011). Even though the reason for the decline on Abaco has not been fully settled, it is likely that predation by cats played a major role, together with a high frequency of hurricanes of category 3 or higher (S. Johnson pers. comm. 2021).
This species inhabits all habitat types present on Andros, mostly pine forests and wetlands, and less frequently developed, agricultural and coppice habitats (Rowley et al. 2021). It preferably nests in pine forests of Caribbean pine (Pinus caribeaea) with an open understory of tall thatch palms, using both pines and thatch palms as nesting trees (Stonko et al. 2018; Yancy et al. 2020). Until recently, it had been assumed that the species depended heavily on anthropogenic, converted habitats and introduced coconut palms (Cocos nucifera) for nesting (Currie et al. 2005; Price et al. 2011; Raza et al. 2020); however this assumption was based on studies focussing mainly on settled areas, leaving pine forests under-surveyed (Stonko et al. 2018). The species breeds between March and August, with a peak in May-July; the nest is an enclosed basket made from plant fibres (Raza et al. 2020).
The species feeds on arthropods, but also takes fruits and nectar and is sometimes seen on nectar feeders in towns (Raza et al. 2020).
The species is facing a variety of threats, including habitat loss, hurricanes and salt water inundation, predation and nest parasitism.
Pine forests are being cleared for agriculture. An increased fire frequency through intentional burning can destroy key thatch palm understory, which is a preferred nesting habtiat, and convert pine forests into herbaceous and fern growth. Being among the most fragile ecosystems in the Bahamas, pine forests may take decades to regrow. Invasive plants may further block out pine forest and hinder regrowth (J. Antalffy, K. Omland, B. Watson and S. Johnson pers. comm. 2021).
Hurricanes can have severe impacts on the species and its habitat, and their intensity and probably frequency are projected to increase with climate change (see e.g., Knutson et al. 2010; Walsh et al. 2016; Hall and Kossin 2019). Pine forests show considerable storm resilience; however, they are very sensitive to flooding and saltwater inundations, as these can irreversibly damage pine forests (J. Antalffy, K. Omland, B. Watson and S. Johnson pers. comm. 2021). Andros is moreover very susceptible to sea-level rise; a rise of 1 m will lead to a 30% decrease in land area (J. Antalffy, K. Omland, B. Watson and S. Johnson pers. comm. 2021).
Predation by invasive cats, which are widespread across Andros, and potentially feral dogs, black rats and raccoons are an additional threat (J. Antalffy, K. Omland, B. Watson and S. Johnson pers. comm. 2021). Introduced corn snakes are currently not considered a severe threat. Native Bahamian Racers prey on fledglings on the ground, while the nocturnal Bahamian Boas climb take roosting birds and access nests; however, pine tree crowns may be safe from snakes (J. Antalffy, K. Omland, B. Watson and S. Johnson pers. comm. 2021).
Particularly in developed areas, nests are parasitised by Shiny Cowbirds (Molothrus bonariensis); about 75% of nests in coconut palms were found to be parasitised, while parasitism in pine forests is much lower or absent (J. Antalffy, K. Omland, B. Watson and S. Johnson pers. comm. 2021). Consequently, planting of coconut palms may be harmful to the species, while the yellowing disease which rapidly destroys coconut plantations may be beneficial.
Conservation Actions Underway
The Bahama Oriole Project, a collaboration between the University of Maryland Baltimore County and the Bahamas National Trust is leading research into this species's population size, habitat use, behaviour and threats, with the aim of developing a conservation strategy to reverse the population decline. Education projects aimed at raising awareness for the species and its habitat are carried out in local communities. Parts of the range are protected within Blue Holes and West Side National Parks and Crab Replenishment Reserve.
Conservation Actions Proposed
Carry out further survey work to confirm the population size. Monitor population trends. Investigate the impact of cats and other invasive and native predators on the population size. Examine the feasibility of translocating the species to Abaco, from where it has been extirpated.
Protect native pine forest habitat. Discourage the creation of coconut palm plantations. Discourage intentional burning of thatch palm understory. Consider restoring pine forests where feasible. Consider controlling invasive plants and mammals. Continue environmental education programmes to raise awareness for the species and its habitat.
20-22 cm. A slender-billed oriole with an obviously decurved culmen. Head and body black with yellow underparts from the pectoral line back to the undertail coverts. There is a brown or greenish wash to the back. On the upperparts the lower back, rump and uppertail coverts are yellow. The wing linings are also yellow. The greater coverts, remiges and rectrices have white tips and fringing. Females are similar to males but have a duller, paler back. Juveniles and immatures have olive to olive-grey upperparts and greenish-yellow underparts and rump. They acquire more black plumage with age, first on the lores and throat. Bill black with bluish-grey basal half to lower mandible; legs grey-blue; iris dark brown. Similar spp Unlikely to be confused with any other species in its range. Voice Calls include a hard keek or check.
Text account compilers
Hermes, C.
Contributors
Antalffy, J., Cant-Woodside, S., Clark, J., Hayes, W.K., Johnson, S., Khwaja, N., Omland, K., Price, M., Sharpe, C.J., Symes, A., Taylor, J., Watson, B. & Wheatley, H.
Recommended citation
BirdLife International (2024) Species factsheet: Bahama Oriole Icterus northropi. Downloaded from
https://datazone.birdlife.org/species/factsheet/bahama-oriole-icterus-northropi on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.