Justification of Red List Category
This species qualifies as Endangered because it has a very small range, which is severely fragmented, and in decline.
The estimate of 930-1,300 mature individuals (roughly equivalent to 1,400-2,000 individuals in total) was estimated based on 712 calling males found within 66% of the suitable habitat within its known range.
This species's population is suspected to be in decline owing to the continued loss and degradation of its habitat for residential, industrial and recreational development, amongst other related and unrelated threats.
This species probably formerly occupied large areas of Puerto Rico (to U.S.A.), but its current distribution was recently thought to be restricted to the south-west, notably Susúa-Maricao, Guayanilla-Peñuelas and Guánica-Bermeja. However, recent survey work confirms that its range extends throughout most of the southern coast of Puerto Rico (Vilella and González 2009). There are further recent records from the Parguera Hills and Sierra Bermeja, c. 10 km west of Parguera. Studies in 1985-1987, 1989-1990 and 1992 found 712 singing males in 98 km2 of fragmented habitat, with 347 in the Guánica area, 177 in the Susúa-Maricao area and 188 in the Guayanilla area. The population was consequently estimated at 1,400-2,000 individuals, which is similar to the 1984 population estimate of 670-800 pairs (Vilella and Zwank 1993a).
The historical range probably comprised moist limestone and coastal forest in northern Puerto Rico, as well as currently occupied dry limestone forest, drier sections of the lower cordillera forest and perhaps dry coastal forest. It is presently more abundant in closed canopy dry forest on limestone soils, composed mainly of semi-deciduous hardwood trees with abundant leaf litter and an open understorey (little or no ground vegetation) at elevations up to 620 m asl, but more commonly above 75 m asl. It occurs at lower densities in dry, open, scrubby secondary growth, xeric or dry scrubland, open scrub-forest and thorny forest undergrowth, with a few birds in Eucalyptus robusta plantations (Cleere and Nurney 1998). Breeding occurs between late February and early July, mainly between April and June (Vilella 1995). Nests are common at elevations above 100 m asl and are characterised by a deep layer of leaf litter and an open midstorey beneath a closed canopy (Vilella 2008). Birds are perhaps permanently territorial, exhibiting strong interannual site fidelity. In Guánica forest, c. 87% of nests in one year produced at least one fledgling (Vilella 1995). It feeds on beetles, moths and other insects (Cleere and Nurney 1998).
Large scale deforestation of Puerto Rico during the late 19th and early 20th centuries reduced nightjar habitat to a small number of isolated fragments. The introduction of the mongoose in 1877 may have contributed to the initial drastic population decline (there are no data on its initial effect), but the differing habitat preferences of the two species suggests very little overlap in their current ranges (Vilella and Zwank 1993b).
Nowadays, habitat loss and degradation are the main threats, especially from residential, industrial and recreational expansion, with concomitant increases in disturbance and fire risk (Vilella 1995). This is particularly relevant as a landscape habitat model estimated greater amount of nightjar habitat outside protected areas (F. Vilella in litt., 2016). Grass fires started by local people occasionally spread to adjacent forest, with fires that occur during periods of low rainfall being particularly damaging (S. A. Colón López in litt. 2011). A proposed windfarm development in the Karso del Sur IBA has the potential to wipe out 5% of the total breeding population (Anon. 2007). Young birds are predated by Short-eared Owl Asio flammeus, and young and eggs may be predated by Pearly-eyed Thrasher Margarops fuscatus, fire-ants and feral cats (Cleere and Nurney 1998). The proposed construction of a natural gas pipeline in the Guayanilla Hills would create significant disturbance to breeding nightjars and destroy and fragment tracts of the species's habitat (C. A. Delannoy in litt. 2012).
Conservation Actions Underway
It is legally protected. Guánica, Susúa and Maricao are public lands designated as state forests, and Guánica is a biosphere reserve. The Conservation Trust of Puerto Rico has acquired lands in the Guayanilla-Peñuelas region; this area includes mature dry forest where nightjars are abundant. The latter constitutes the only protected nightjar habitat in this portion of its range. The population is not regularly surveyed, but spatial analysis has identified areas of potentially suitable habitat for protection and examination of changes in habitat cover over time (F. J. Vilella in litt. 2016). As part of BirdLife International's Preventing Extinctions Programme the Sociedad Ornitológica Puertorriqueña, Inc. has been designated as Species Guardian and have produced a revised species action plan in collaboration with the U.S. Fish and Wildlife Service. A survey of occupancy of habitat in order to establish current range was carried out by Mississippi State University between March and May 2009 (Vilella and González 2009). The priority conservation actions identified by the species action plan will be implemented through a newly-established Puerto Rican Nightjar Conservation Network and facilitated by the Species Guardian.
22 cm. Mottled grey, brown and black nightjar. Black throat bordered by white band. White in outertail. Female similar, but buff throat-band and outertail. Similar spp. Chuck-will's-widow C. carolinensis (northern migrant in winter) is larger, more reddish and has less white in tail. Antillean Nighthawk Chordeiles gundlachii has distinctive white patch in wing. Voice Sequence of emphatic whistles whip whip whip ... (between 2-15 notes, males may also sing continuously for several minutes with up to 160 notes).
Text account compilers
Benstead, P., Bird, J., Butchart, S., Calvert, R., Capper, D., Sharpe, C J, Symes, A., Taylor, J., Wege, D., Khwaja, N. & Wheatley, H.
Colón López, S., Vilella, F., Delannoy, C. & Cleere, N.
BirdLife International (2020) Species factsheet: Antrostomus noctitherus. Downloaded from http://www.birdlife.org on 10/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 10/08/2020.