NEST AND CHICKS OF Pseudoscops clamator (AVES: STRIGIDAE)IN THE HIGHLAND PLATEAU OF THE SABANA DE BOGOTÁ, COLOMBIA

Nido y polluelos de Pseudoscops clamator (AVES: STRIGIDAE) en el altiplano de la sabana de Bogotá, Colombia

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The Striped Owl Pseudoscops clamator (Vieillot, 1807) is a Neotropical resident bird, occurring from southern Mexico to northern Argentina, with a disjunct distribution in northern South America (del Hoyo et al., 1999;Thurber et al., 2009;Enríquez, 2015). This owl inhabits forests, open ecosystems, pastures, crops, wetlands and urban parks (Thurber et al., 2009). It is mainly nocturnal but occasionally hunts during the daytime and at dusk, preying upon birds, insects and small rodents (Delgado et al., 2005;Thurber et al., 2009;Lo Coco et al., 2012; Chaparro-Herrera et al., 2015). Despite its wide geographic range, there is scarce information on its nesting ecology and reproductive biology. Recent studies have documented the diet and reproduction of P. clamator in Central America, Brazil, Argentina and Colombia (Isacch et al., 2000; Pautasso and De la Peña 2001;Motta-Junior et al., 2004; Delgado et al., 2005; Thurber et al., 2009;Tittarelli and Villarreal 2009). The records for P. clamator in Colombia come from Sinú-Córdoba, the Cauca River watershed, the city of Medellín, and the Sabana de Bogotá (Hilty and Brown 1986; ABO 2000; Delgado et al., 2005;Estela and López-Victoria, 2005; Botero and Jaramillo, 2011). These areas have been highly transformed by agricultural activities and urban expansion (Etter and van Wyngaarden, 2000; Camargo-Ponce de León, 2007). In particular, the Bogotá highland plateau in the Eastern Andes, is inhabited by more than eight million people (DANE, 2009), and only a few isolated remnants of natural ecosystems remain. However, despite such profound modifications, this area still harbors around 200 bird species, including the Striped Owl (ABO, 2000). This owl was first recorded in the Bogotá highland plateau in 1997 at the Conejera wetland, and probably reproduced there in 1998 (ABO, 2000). Since then, this owl has been recorded more frequently and has become a resident bird, present in several areas dominated by pastures and wetlands, but there is no documented information on its reproduction in this geographical area. Here, we report the nest, eggs, and chicks of P. clamator in a suburban area of the Bogotá highland plateau.

Our study was carried out during April and May 2013 in the campus of Universidad Militar Nueva Granada, municipality of Cajicá, department of Cundinamarca, Colombia (4°56′34′′N, 74°00′43′′W; ∼2550 m a.s.l.). The campus covers 75.5 ha and is dominated by pastures of Cenchrus clandestinus that cover nearly 70 % of the area (Sánchez et al., 2015). The remaining area of the campus consists of buildings, roads, greenhouses, and scattered gardens; as well as several artificial wetlands under the influence of the Bogotá River on the eastern border of the campus (Barrera-Niño and Sánchez, 2014). There is also a plantation of Eucalyptus globulus, covering almost 400 m2 near the river, with 10-15 m high trees and a ground cover dominated by grass, C. clandestinus, 30-50 cm high; as well as patches of secondary growth containing trees such as Diplostephium sp. and Baccharis spp., patches of Rubus sp., and Phytololacca sp. shrubs. Scattered throughout the Eucalyptus plantation there are also planted trees of Cedrela montana, Duranta mutisii and Senna sp. (Sánchez et al., 2015).

We found a nest with two chicks on 5 April 2013 in the Eucalyptus plantation (Fig. 1A). We made observations of the nest, using Bushnell® binoculars (10 × 42mm) and a Canon® camera EOS Rebel T3i with EF 70-300mm lens, and followed the chicks' development. Every twenty days, we registered visible features as changes in plumage coloration, body size and vegetation cover, around the nest site.

The nest was at the base of a Eucalyptus tree, without much elaboration and with some leaf litter and chick feathers (Fig.1B y 1D). The nest was 20-30 cm in diameter with 50 cm tall grasses surrounding it. On a second visit on April 25th, we only found one juvenile and one adult. The adult made a defensive display extending its wings and oscillating its body, without making any alarm call during our observations (Fig. 1E). On May 5th the nest was found to be empty, and we did not record the presence of either the juvenile or the adults (Fig. 1B). We also found two eggs on the ground next to a Eucalyptus tree on 5 May 2013, 12 m away from the nest site of P. clamator described above. Its location and the fact that leaf litter and some feathers belonging to P. clamator surrounded the eggs, suggested that they belonged to P. clamator (see Martinez et al., 1996;Tittarelli and Villarreal, 2009;Enríquez, 2015). The eggs were ellipsoid, and white but stained on the sides by ground material. One of the eggs was broken, possibly predated, and the other was complete but dried (Fig. 1C). The broken egg measured 42.1 × 35.5 mm the other 42.4 × 35.1 mm (Fig. 1C). These measurements are within the range recorded for P. clamator eggs (Thurber et al., 2009). These eggs were collected and stored at the ecology and biodiversity laboratory in the Universidad Militar Nueva Granada.

Based on our observations on April 5th and the information in Holt et al. (1992) and Martínez et al. (1996), we estimated that the two chicks were eight to ten days old, since they had white downy plumage covering most of their bodies, salmon coloration on the dorsum, gray-black beak, open eyes, but could not yet rise on their own legs (Fig. 1D). According to our previous estimation the chicks were 25 to 30 days old on April 25th, since the chick had yellow-ochre feathers on the dorsum and belly, with some salmon tint, incomplete and not well defined facial disk, rufous eyes, and black spots that covered ∼60 % of the facial disk (Fig. 1E).

We also found 30 owl pellets 15-20 m from the nest with chicks (data not analyzed), and next to them a carcass of a Brazilian guinea pig Cavia aperea (Fig. 1F) and feathers of Eared Dove Zenaida auriculata. The carcass was identified using Zúñiga et al. (2002) and the feathers based on our personal field experience. The measurements of the nest described here, as well as the vegetation characteristics around it, are similar to descriptions of P. clamator nests in other geographic areas in Argentina, Brazil and Suriname (Haverschmidt, 1968;Wetmore, 1968;Blendinger et al., 1987; Martinez et al., 1996;Tittarelli and Villarreal, 2009). Elsewhere, nests have been recorded close to the ground, but typically on thick branches ∼45 cm above the ground. Finding only one juvenile on our second visit suggests that one of them died, as has been reported for other owl species (del Hoyo et al., 1999). The defensive display, spreading the wings from side to side has been described previously for P. clamator (Thurber et al., 2009), and appears to be a common behavior for several owl species (del Hoyo et al., 1999).

According to the literature, P. clamator juveniles leave the nest after 25 to 30 days (Thurber et al., 2009), which likely explains why the nest was empty 30 days after the first observation of the chicks. Incubation in this species has been estimated at 30 to 33 days (Thurber et al., 2009), suggesting that eggs were probably laid at the beginning of March. A clutch of two has been reported previously, though two to four eggs may be laid and is considered normal. A clutch of 2-3 eggs appears to be typical in northern South America, but up to five eggs have been recorded in Argentina (Wetmore, 1968;Haverschmidt, 1968;Blendinger et al., 1987; Martinez et al., 1996;Pautasso and De La Peña, 2001; Thurber et al., 2009; Tittarelli and Villarreal, 2009).

In the Bogotá highland plateau there may be more than one reproductive cycle per year, since chicks and juveniles have been recorded both at the beginning and at the end of the year in several wetlands in the city of Bogotá (S. Córdoba-Córdoba, pers. obs. Feb, 2014). The occurrence of P. clamator both in urban and suburban areas in the Bogotá highland plateau suggests that P. clamator is able to successfully inhabits moderately, human-transformed environments, making it possible for this species to expand its distribution even to high mountain areas, where it was not previously recorded. Food availability may limit the nesting possibilities for this species and it may be restricted to areas near aquatic environments, probably due to the presence of rodents such as C. aperea, which are mostly found in wetlands in the Bogotá highland plateau (Sánchez, 2010; Mendoza and Sánchez, 2014). Our results are complementary to those presented for other nests near water courses and lakes, such as in Argentina (Blendinger et al., 1987;Martínez et al., 1996;Pautasso and De La Peña, 2001; Tittarelli and Villarreal, 2009), even though the Striped Owl may also reproduce in forests and open areas with shrubs and herbaceous vegetation (Tittarelli and Villarreal, 2009; Chaparro-Herrera et al., 2015). However, the timing of reproduction in the Bogotá highland plateau should be studied, as well as prey selection, since the reproduction of this species has been reported to be prey dependent (Pautasso and De La Peña, 2001). Consumption of rodents such as C. aperea, with a body mass of 270-720 g (Morales et al., 2004), suggests that P. clamator (body mass ca. 350-485 g–Dunning 2007) is able to capture big preys, and probably requires such prey items to have a positive reproductive fitness, as proposed by Pautasso and De La Peña (2001) and Motta-Junior et al. (2004). Other prey items reported for the Bogotá highland plateau, such as rodents, including Rattus rattus, R. norvegicus and Mus musculus (Sánchez, 2010), may also help fulfill the energetic requirements for a successful reproduction (Pautasso and De La Peña, 2001).

Figura 1
Pictures of the study site and of the nest and chicks of Pseudoscops clamator in the campus of the Universidad Militar Nueva Granada in the Bogotá highland plateau, Eastern Andes, Colombia. Eucalyptus globulos plantation where the nest was found(1A). Nest on the ground (1B). Abandoned eggs (1C). Chicks on nest (1D). Juvenile and adult making defense display (1E). Carcasses of Brazilian guinea pig Cavia aperea found near the nest (1f).

The authors declare that they have not conflict of interest.

Universidad Militar Nueva Granada for funding the project CIAS 1180 "Plantas, aves y mamíferos del campus Cajicá", during which the data were taken. Daniela Cortes and Nicolás Cepeda helped during fieldwork. Nick Bayly made useful comments on an early version of the manuscript and English version. Thanks to the anonymous reviewers, which made valuable comments, suggestions, and proofread the manuscript. There are no conflicts of interests for the publication of this paper.