Puerto Rican Nightjar Antrostomus noctitherus

  • Order: Caprimulgiformes
  • Family: Caprimulgidae
  • Monotypic
  • Authors: Francisco J. Vilella
Sections

Breeding

On leaf litter. 1-2 eggs. Puerto Rican Nightjar nests have been located (first egg laid) between 24 February and 1 July, with the peak of nesting activity from April through June. This 3-month period includes the bulk of the nightjar's known nesting dates. Like other caprimulgids, the nightjar does not construct a nest as such; the female merely lays the eggs directly on supporting leaf litter. Nests are never found in exposed areas or clearings, clutches consist of 1-2 eggs, most nests (83%) consist of two egg clutches (Vilella 1995). Puerto Rican Nightjar nest, Guánica Forest. Photo: Mike MorelEggs are buffy brown with numerous brownish purple spots over the entire surface (Kepler and Kepler 1973, Vilella 1995). However, there is variability in the amount of spotting, with some eggs being paler and less speckled than others. Eggs appear only moderately cryptic on the substrate; however, incubating adults provide excellent concealment through their cryptic plumage. Nightjars sit tightly on the eggs during the day and hold their body pressed to the ground, enhancing their inconspicuousness. Puerto Rican Nightjar on nest, Guánica Forest. Photo: Mike Morel

Males of various nightjar species have been documented sharing incubation and brooding duties with the female (Cink 2002, Wilkinson 2009). Puerto Rican Nightjar males actively incubate and brood during daylight hours (Vilella 1995, Delannoy 2005). Incubating adults remain on the eggs even when closely approached. However, if approached within a meter, the adult will usually flush from the nest. When flushed, incubating males fly up abruptly, landing a few meters from the nest. Once on the ground, they spread their tail and wings widely, the white tail patches very conspicuous at this time. The bird vibrates its body and hops, drawing attention away from the nest. This display varies in intensity depending on the phase of the incubation period and the frequency of visits by the observers, as it does in other caprimulgid species (Cink 2002). Relief of incubating and brooding males by the female occurs frequently during crepuscular hours. Puerto Rican Nightjar males attending nests become restless as neighboring singing activity increases; females will approach the male who displays briefly before flying off (Vilella 1995). Puerto Rican Nightjar displaying during nest relief, Guanica Forest. Photo: FJ Vilella

Eggs hatch after an 18-20 day incubation period; most hatching occurs from March to July. Brooding is most common during May and June. Puerto Rican Nightjar chicks resemble the young of the Whip-poor-will (Caprimulgus vociferus) (Cink 2002). Puerto Rican Nightjar chicks, Guanica Forest. Photo: Mike Morel
As with incubation, Puerto Rican Nightjar males are actively involved in brooding and care of the young. Chicks are fed by regurgitation throughout the night. During twilight hours, both members of the pair alternate feeding the chicks. Chicks are capable of short-distance movements within 24 hours of hatching. Adult nightjars land a short distance from the chicks and utter soft clucking sounds to which the chicks respond. These initial movements are seldom greater than 50 cm from the original nest site (Vilella 1995). As they develop chicks move increasingly farther away from the original nest site. By the time they are 14 days old they have moved several meters from the location of the nest. Brooding male Puerto Rican Nightjar with 14-day old chick, 20 June 2010 Guanica Forest. Photo: Mike MorelBrooding males do not sing for prolonged periods of time during twilight hours, and when they do, it is often away from the chicks. Juvenile nightjars remain within the territory of the nesting pair for some time (≥1 month) after fledging (Vilella 1995).Adult (left) and juvenile (right) Puerto Rican Nightjars. 22 March 2009, Guanica Forest. Photo: Mike MorelWhen a brooding nightjar is disturbed it engages in prominent displays, similar to those observed during the incubation phase, except they are more intense and last for longer periods of time. Also, distraction displays during brooding frequently occur at greater distances and often above ground on tree branches. Puerto Rican Nightjars engage in intense distraction displays during the brooding phase, Guanica Forest. Photo: FJ VilellaPuerto Rican Nightjar pairs exhibit strong site fidelity to nesting sites. Nightjar males maintain small home ranges during the breeding season (Vilella 1995). Two males fitted with radiotransmitters for up to 24 days averaged 65.8 ± 7.5 m/movement. Home ranges for the radiomarked males were 4.8 ha and 5.6 ha. Puerto Rican Nightjar (center) using limestone substrate as nesting cover, Guanica Forest. Photo: FJ Vilella Nightjar nests sites are located within a meter of the base of a small tree. However, on rare occasions nesting nightjars will use alternate substrates for cover such as overhanging limestone. Nightjar nests in evergreen forest have greater leaf litter biomass than nests in semi-deciduous forest. Puerto Rican Nightjar nest site selection is best described by increasing leaf litter biomass, decreasing midstory stem density, and increasing canopy closure (Vilella 2008). Nightjar nest site in semi-deciduous forest, Guanica Biosphere Reserve. Photo: Armando Feliciano

Recommended Citation

Vilella, F. J. (2010). Puerto Rican Nightjar (Antrostomus noctitherus), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.purnig1.01