The monotypic oilbird, Steatornis caripensis (Steatornithidae, Caprimulgiformes), is unique for being the only nocturnal frugivorous bird worldwide. It is distributed locally in the Andes between Venezuela and Bolivia, in the coastal cordilleras of northern Venezuela, on tepuis in southern Venezuela and the Guayanas, and in Trinidad (Meyer de Schauensee and Phelps 1978; Bosque 1986; Hilty and Brown 1986; Thomas 1999; Herrera 2003; Hilty 2003). The distribution seems to be mainly limited by caves and large cave-like crevices that are used for breeding and diurnal roosting. Records of oilbirds in the Amazon lowlands are extremely rare, most likely due to the lack or scarcity of suitable caves. Table 1 summarizes the respective information available for western Amazonian Peru and Brazil. For the State of Amazonas in Venezuela, records of oilbirds unrelated to known colonies are provided by Bosque (1986). Diego Calderón Franco (personal communication to EWH) has gathered information on oilbirds in lowland Colombian Amazonia, indicating their presence at Vereda los Alpes (Municipio Doncello, Caquetá; O. Cortes personal communication to Diego Calderón Franco), Cartagena del Chaira and Belén de los Andaquíes (both Caquetá; A. Hernández personal communication to Diego Calderón Franco). Additionally, stomach contents of individuals from Parque Cueva de los Guacharos contained seeds of Amazonia-restricted plants, indicating distribution all along the Colombian Amazon (F. Estela pers. comm. to Diego Calderón Franco).

Table 1 Records of oilbirds from lowland Amazonia of Peru and Brazil
Full size table

Here we report on a sighting and video record of an oilbird at the Estación Biológica Quebrada Blanco (EBQB) in northeastern Peruvian Amazonia. The EBQB site is located at 4°21′S 73°09′W, at an altitude of about 120 m a.s.l. It is characterized by high-ground forest (terra firme or “bosque de altura”, Encarnación 1985), interspersed with small swampy areas, mainly along small creeks.

The sighting was made on 22 September 2006 at 8:45 a.m. while the first two authors were following a habituated mixed-species troop of tamarin monkeys (Saguinus fuscicollis and Saguinus mystax). The first author detected an oilbird sitting on a horizontal branch at about 3 m height above ground. When a saddle-back tamarin, Saguinus fuscicollis, wanted to pass on the same branch, the bird flew to a slightly higher branch where it started swinging left and right with its head narrowed, looking at the observers. The saddle-back tamarin approached the bird from below and tried to touch it, reaching within about 20 cm from the bird’s tail. After the tamarin was joined by two more members of its group, the bird flew to another tree and settled on a branch at about 5 m above ground, where it resumed the swinging movements. It remained there although the second author approached to within 3 m to make a video recording (see http://www.soziobio.uni-goettingen.de/Peru/Birds or http://www.soziobio.uni-goettingen.de/Peru/voegel for the video). Observation and video recording were suspended after about 10 min when the authors moved on with the tamarin monkey troop.

Oilbirds have been observed at feeding localities up to 150 km away from their roosting caves, and in Costa Rica they have been recorded around 700 km away from the nearest known cave in Colombia (Thomas 1999; Hilty 2003). The latter may suggest an unknown local breeding colony rather than a migrant from Colombia (Thomas 1999). A single marked oilbird flew 240 km in a single night from one cave to another (Roca 1994). At the Caripe cave in Venezuela, post-breeding migration occurs, perhaps due to the local loss of food resources, but distances have not been reported (Bosque 1988). “Nomadism” is particular in juveniles, but other movements are poorly known (Thomas 1999).

Palmari Lodge on the Rio Javari and the Paucarillo Forest Reserve on the Rio Orosa from where oilbirds have been reported are about 320 km and about 130 km, respectively, from EBQB (Whittaker et al. 2001; see Table 1). The distance from EBQB to the Andean foothills is about 600 km. Oilbirds are capable of flying distances of 240 km in one night (Roca 1994), and thus could reach EBQB and the other areas within three nights when coming from the Andes. Alternatively, the bird might have reached EBQB from caves that apparently do exist east of the Rio Ucayali at the Serranía de Contamana and the Sierra del Divisor (Table 1), about 400–500 km south of EBQB. Finally, the relative proximity of the records from the Rio Javari, Rio Orosa and EBQB might indicate the existence of a currently unknown breeding colony in the lowland Amazonia. If so, its survival would depend on the availability of nutritional resources that are within their dietary range. At EBQB a number of plant genera is present that have been reported as food for oilbirds by Snow (1962) and Bosque et al. (1995): Nectandra and Ocotea (Lauraceae), Virola (Myristicaceae), Tapirira (Anacardiaceae), Pouteria (Sapotaceae), Cordia (Boraginaceae), Bactris, Euterpe, Geonoma and Oenocarpus (=Jessenia) (Arecaceae). Several of these genera are very widespread and abundant in lowland Amazonia (Gentry 1993) and could probably sustain local populations of oilbirds and vagrants that have migrated into these areas.

Considering all information compiled in this report together, oilbirds seem to occur in lowland Amazonia more regularly than previously known.

Oilbirds disturbed in their caves respond strongly with loud vocalizations. We are not aware of descriptions of responses to disturbances outside caves. The response of the oilbird in our observation was moderate and consisted only in short displacements. Apparently, the tamarins were not conceived as a serious threat. Although tamarins prey on small vertebrates, including nestling birds (Heymann et al 2000), it is unlikely that they would have attacked the oilbird.

Zusammenfassung

Sichtung und Videodokumentation eines Fettschwalms, Steatornis caripensis, im peruanischen Amazonastiefland

Wir berichten über die Sichtung eines Fettschwalms, Steatornis caripensis, im peruanischen Amazonastiefland im September 2006 und diskutieren diese im Zusammenhang mit Informationen über weitere Sichtungen von Fettschwalmen im Amazonastiefland. Zusammengenommen weisen die vorliegenden Informationen darauf hin, dass Fettschwalme offenbar häufiger im Amazonastiefland vorkommen als bislang angenommen.