Distribution in the Americas
Endemic, non-migratory. The Puerto Rican Nightjar is endemic to Puerto Rico. The species was first described from a previously misidentified skin collected in Bayamón near San Juan in 1888, a collection of sub-fossil bones from cave deposits in the wet karst region of north-central Puerto Rico, and a record of a bird seen in wet karst forest near Rio Piedras in 1911 (Wetmore 1919, 1920). Therefore, all the initial locality information for the nightjar was from the northern region of the island. Following these initial records the species went unrecorded for many years and was presumed extinct following the introduction of the small Indian mongoose Herpestes auropunctatus around 1877 (Vilella and Zwank 1993b). In 1961 the species was found in Guánica Forest, located 62 km to the southwest of the last recorded sighting 50 years earlier (Reynard 1962). The long period of presumed extinction, and the limited knowledge of its biology and distribution led to the species being listed as Endangered by the U.S. Fish and Wildlife Service, the International Union for the Conservation of Nature, and the Puerto Rico Department of Natural and Environmental Resources (Díaz 1983, BirdLife International 2011).
The first detailed study on the nightjar was conducted from 1969 to 1971 by Kepler and Kepler (1973). In addition to Guánica Forest, they found nightjars in the Susúa Forest and reported hearing them from the road near the Guayanilla Hills, but conducted no formal surveys there. A more extensive study on relative abundance and geographic distribution was conducted during 1985-1992 in an expanded number of localities across southwest Puerto Rico, and also included searches in historical habitat on the moist karst forest of the island's north-central region (Vilella and Zwank 1993a). No relict populations were found in the northern moist karst forest region of the island. Nightjars were found in three main areas located in coastal dry and lower cordillera forests of southwestern Puerto Rico. These included; Guánica-Ensenada, Susúa-Maricao, and Guayanilla-Peñuelas. This study also reported the first nightjar records in the Parguera Hills and Sierra Bermeja, located on the southwestern tip of Puerto Rico (Vilella and Zwank 1993a).
Research on nightjar occupancy outside forest reserves and formerly reported locations indicated the species' geographic range was considerably different from what had been previously estimated (Vilella and González 2009). Nightjar presence was detected in 12 of 18 municipalities across southern Puerto Rico.
Dry coastal and lower montane forests. At Guánica Forest, Puerto Rican Nightjars are most abundant in semi-deciduous and evergreen forests above 75 meters in elevation. Approximately 35% of the 246 tree species at Guánica Forest are deciduous during the dry season. The dominant plant families are Fabaceae, Euphorbiaceae and Myrtaceae (Lugo et al. 1996). Semi-deciduous forest is characterized by shallower slopes where the tree species Bursera simaruba and Bucida buceras constitute the emergent overstory. This association also is characterized by the layering of the forest, with a shorter layer of shrubs and trees found under the emerging canopy. The most common plant species of the midstory include Coccoloba microstachya, Coccoloba krugii, Colubrina elliptica, Plumeria alba, and various species of Capparis.
Evergreen forest occurs at higher elevations in areas with deeper soils and greater moisture. This forest is dominated by some of the same species found in deciduous forest plus evergreen species such as Krugiodendron ferreum, Amyris elemifera, Guaiacum officinale, Guaiacum sanctum, Coccoloba diversifolia, and several species of Eugenia. During the 1930’s, plantations of Dominican mahogany (Swietenia mahogani) and logwood (Haematoxyumn campechianum) were established in areas of evergreen forest. Over time these have developed into mature evergreen forest mixed with mahogany and logwood in the overstory. The mixed plantation-evergreen forest at Guánica Biosphere Reserve harbor the highest densities recorded for the Puerto Rican Nightjar (Vilella and Zwank 1993a, Gonzalez 2010) and also includes the greatest number of nightjar nests documented to date (Vilella 2008).
Below 75 meters elevation Guánica Forest is dominated by xeric coastal scrub and cactus dominated vegetation. While Puerto Rican Nightjars occur in lower numbers within coastal scrub, no nests have been located at these lower elevations (Vilella 1995). Coastal scrub is characterized by exposed limestone with occasional solution holes and shallow soil pockets. As a result, these areas have few widely spaced deciduous trees (Bursera simaruba, Plumeria alba) among which are interspersed many shrubs, grasses, cacti (Pilosocereus royenii, Melocactus intortus ) and areas of exposed limestone, providing virtually no usable nesting habitat for the Puerto Rican Nightjar.
Puerto Rican Nightjars also occur in the higher elevation forests of Susúa and Maricao. Susúa Forest represents a transitional zone between the dry forests of the coast and the moist forests found in the mountains of the Cordillera Central. Susúa Forest was established as a reserve in 1935 and is located within the southwestern serpentine and volcanic region of the island (Silander et al. 1986). Steeper than Guánica, most of the ridges and slopes are covered with dry forest vegetation similar in structure to Guánica Forest with a canopy height reaching up to 6 m.
Puerto Rican Nightjars are most abundant in the southern regions of Susúa Forest. Throughout the reserve, nightjars are restricted to drier forest found on the steep slopes and ridges. Susúa Forest includes approximately 157 tree species, of which 18 are classified as rare or endangered. Ridgetops and slopes are dominated by Coccoloba mycrostachya, Machonia portoricensis, Ouratea litoralis, and Cassine xylocarpa. (García 1991). Unlike Guánica, a number of rivers drain Susúa Forest where riparian habitats are dominated by moist forest with a tree canopy reaching 15 meters. Riparian forest is dominated by Neolauregia resinosa, Rondeletia inermis, Rheedia hessi, and Pimenta racemosa (García 1991). Puerto Rican Nightjars are not found in the moist forest of Susúa, nor do they use gallery forest found along rivers. Puerto Rican Nightjars range beyond the northern boundaries of Susúa Forest. The highest elevation (640 meters) where nightjars have been recorded is on the southeastern section of the Maricao Forest (Delannoy 2005). Maricao Forest is a montane reserve located approximately 10 km to the northwest of the Susúa Forest. A Puerto Rican Nightjar nest was located at the edge of a trail on a eucalyptus (Eucalyptus robusta) plantation (Delannoy 2005).
The third major region occupied by the Puerto Rican Nightjar is the dry limestone forests of the Guayanilla-Peñuelas Hills. Nightjars densities in the region of Guayanilla-Peñuelas are second only to the Guánica Forest (Vilella and Zwank 1993a, González 2010). Puerto Rican Nightjars occur throughout the dry forest found along slopes and ridges but are not found in the moist forest and deep canyons of this region.
The dry forests of Guayanilla-Peñuelas are characterized by vegetation very similar to Guánica Forest. Subtropical dry forest is dominated by Pictetia aculeata, Bourreria suculenta, and Croton discolor. A number of areas in this region reflect recent and ongoing disturbance from agriculture. Vegetation is dominated by spiny scrubland typical of disturbed areas and includes Ricinus communis, Sesbania dispinosa, and Prosopis juliflora. The canopy of the semi-deciduous dry forest found on slopes and ridges is dominated by Guaiacum officinale, Comocladia dodonea, and Bursera simaruba. Unique among other dry forest areas of southwestern Puerto Rico, the region of the Guayanilla-Peñuelas Hills harbors karst formations characterized by deep canyons with underground rivers. Vegetation along the canyons is characterized by moist forest.
Based on the earliest records for the species (Wetmore 1919) the historical range of the Puerto Rican Nightjar included both the northern and southern karst forests of the island, and may have ranged into the lower montane forests of the Cordillera Central. While Puerto Rico was practically totally forested at the time of its discovery in 1493, by the early 20th century deforestation had peaked and little original forest cover remained (Wadsworth 1950). Extensive habitat destruction and the introduction of the mongoose may have contributed to the extinction of the species in the northern portion of its historical range.
The mongoose was introduced to the West Indies during the 1870's, a period in which the economy of the majority of the Caribbean islands was based on the production of sugarcane. Damage to this vital crop by rats (Rattus spp.) was severe by 19th century standards (e.g., 150,000 pounds sterling per year in Jamaica). Most Caribbean mongoose are derived from five females and four males brought from India to Jamaica in 1872 by W. Bancroft Espeut, a Jamaican sugar producer. The idea to introduce mongoose came to Mr. Espeut from his wife, who lived for several years in Ceylon (Sri Lanka) and had there possessed a mongoose as a pet. Following published claims of successful rat control in sugarcane fields (Espeut 1882) all Caribbean islands with a major sugar industry introduced mongoose within 30 years of arriving in Jamaica.
Like the rest of the island, southwestern Puerto Rico also experienced extensive habitat destruction. Deforestation in Puerto Rico peaked in the early 1930s when forest cover reached a low of approximately 81,000 ha, representing about 9% of the land (Birdsey and Weaver 1987). However, forest recovery following cessation of intensive land-use has progressed in time and space (Lugo et al. 1996). By the 1980s forest cover, including coffee shade, occupied about 280,000 hectares, about 31.5% of the island's land area (Birdsey and Weaver 1987). Nightjars likely benefited from land-use changes during the second half of the 20th century. Many areas currently occupied by nightjars were probably recolonized once adequate forest structure became established. Unfortunately, there is no information regarding the location and extent of relict nightjar populations that survived this prolonged period of habitat modification and loss.
The only existing fossil information for the Puerto Rican Nightjar are a set of sub-fossil bones (five humeri and one metacarpal) collected by Wetmore during his 1911 visit to Puerto Rico. These were collected from caves in the moist karst forest region of Morovis, located in north-central Puerto Rico (Wetmore 1919). How these bones ended up in cave remains can only be speculated, as Puerto Rican Nightjars are never found near the caves of the Guayanilla Hills. They may represent prey items of the extinct Puerto Rican Barn Owl (Tyto cavatica). Wetmore (1920) described this extinct species of owl from bones collected in cave deposits of Puerto Rico.