Incubation Behavior of Threatened Oreopholus ruficollis in the Atacama Arid Ecosystem During a “Flowering Desert”: Implications for the Future Conservation of the Species

Simple Summary

In this article, the breeding of the Tawny-throated Dotterel (Oreopholus ruficollis) is examined within the “flowering desert”—a rare phenomenon that occurs in rainy years and promotes the growth of ephemeral plant communities—the ecosystem of the Atacama Desert (northern Chile). This increase in vegetation was expected to enhance ecosystem productivity and thereby augment food availability for associated fauna. Fieldwork was conducted at “Llanos del Lagarto” during the flowering period (spring 2025). A camera trap was installed near likely nest sites to document, via motion-activated photographs, parental behaviors associated with egg incubation, nest guarding, and incubation recesses linked to self-feeding. Throughout the monitoring period, the study produced 2160 photographs used for the analysis and identified one nest containing four eggs, located within a crevice and camouflaged amidst vegetation predominantly consisting of Cistanthe longiscapa. Incubation activity occurred primarily from late afternoon into the night, nest guarding was most frequent during the afternoon (peaking at approximately 17:00), and temporary nest absence showed a peak at around 14:00.

Abstract

The Tawny-throated Dotterel is a migratory species listed as “near threatened” in Chile and distributed across diverse ecosystems in South America. However, little is known about its nesting behavior in arid desert ecosystems, where it may utilize certain sporadic vegetation strata for nesting. The Atacama Desert, located between southern Peru and northern Chile, is described as the driest and oldest desert on the planet. Nevertheless, during extraordinary periods of rainfall, this arid zone experiences flowering—primarily in the spring—which can provide an optimal breeding niche for some birds. In this article, we report, for the first time, the discovery of an Tawny-throated Dotterel nest during a “flowering desert” period. The nest was monitored using a camera trap. The egg-incubation frequency observed in our study was mainly distributed during the night, while the adult spent a significant fraction of the day on nesting activities and self-maintenance. Future studies are needed to determine whether this area is indeed a periodic nesting area for the Tawny-throated Dotterel, which would strengthen the designation of this part of the Atacama Desert as a potential conservation area.

1. Introduction

The Atacama Desert, located in northern Chile and southern Peru, is the driest and oldest desert in the world, mainly because of the subsidence of the subtropical anticyclone, the Humboldt current, and the Andes mountain range, the surface of which extends approximately 1400 km² [1,2]. During certain rainy years, this arid zone (with a rainfall of less than 50 mm per year) experiences an unusual phenomenon called the “flowering desert,” which produces ephemeral plant species that cover the desert during spring [3,4]. This phenomenon, characterized by the sporadic flowering of a range of plant species, leads to an increase in the ecosystem’s primary productivity, which, in turn, results in a corresponding rise in populations of fauna associated with this vegetation layer [5]. In this context, the phenomenon provides a unique opportunity to identify nesting areas for bird species since the increased prey availability resulting from the vegetational surge would furnish an optimal niche for the foraging and sheltering of birds during the incubation period [6].

The Tawny-throated Dotterel, of which there are two discontinuous subspecies, is a migratory bird belonging to the family Charadriidae. The northern subspecies, pallidus, inhabits the arid northern Peruvian coast year-round [7]. The southern subspecies, nominate ruficollis (Oreopholus ruficollis ruficollis, Wagler, 1829), breeds in the Patagonian steppe, puna grasslands, and sandy areas with sparse vegetation in the southern Andes of Argentina, Bolivia, Chile, and Peru; its range extends north at least to Lake Junín, and it is also found in the Comechingones Mountains in central Argentina, as well as grassland areas in southern Ecuador and Brazil, where it adapts readily [8,9,10]. Regarding Chile, Jaramillo [11] reported two populations, one in the north and one in the south, with no reference to subspecies. On its distribution map, the northern population extends along the altiplano as far south as about 22°30′ S. The southern population is highly migratory and has a lowland distribution along the coast from south of Antofagasta (24° S) to Pichilemu (34° S). The species’ breeding period in South America typically spans the spring months, although in the high-altitude regions of northern Chile, it can extend into the summer [10].

In Chile, this species is in sharp decline and classified as near-threatened by the Ministry of the Environment, with its main threats including the expansion of agricultural areas, poaching, solar and wind energy projects, and habitat loss [8,12]. Furthermore, its reproductive ecology is unknown, primarily because of the difficulty of locating its nesting areas in the field and population decline with respect to this species [13]. Previous research has shown that “Mediterranean” and mountainous grasslands are preferred habitats for nesting [14,15], so we sought to determine the nesting presence of this species during the flowering-desert phenomenon and describe reproductive and daily behavior, at the parental level, in the nest using a camera trap configured to allow detection of the parent bird’s movements. It is unknown whether the Tawny-throated Dotterel can use areas near the “flowering desert” for breeding at the study site, a relevant consideration since this area is designated as a priority conservation site by the Chilean government [16].

2. Materials and Methods

2.1. Study Area

This study was carried out in “Llanos del Lagarto” village (UTM 19S 325125 E/6881918 N), located approximately 35 km north of Vallenar in the Atacama Desert, northern Chile. During the study, a moderate flowering-desert phenomenon occurred from September to December 2025, characterized by the massive flowering of species that covered the area with a stratum of approximately 25 cm in height (Figure 1). In this area, a grid of roughly 370 ha was established to survey nests of the focal species. The sector is characterized by extreme aridity and classified as a transitional desert, with a mean annual precipitation of around 40 mm [17], supporting a vegetation stratum composed of grasses and shrubs predominantly consisting of Cistanthe longiscapa, Cristaria gracilis, and Balsamocarpon brevifolium. This area has been designated as a priority conservation area owing to the presence of endemic species at risk, which are associated with the phenomenon known as the “flowering desert,” which typically occurs during periods of elevated precipitation or under the influence of climatic phenomena such as the El Niño–Southern Oscillation [16].

2.2. Reproductive Behavior

Following grid establishment, in October 2025, we conducted systematic field surveys to determine the presence of the adult Tawny-throated Dotterel within the study area. Owing to the large extent of the surveyed area (370 ha), a team of five researchers conducted random field surveys for 6 h per day during the first four days of October 2025.

Subsequently, we monitored the acoustic and physical courtship/breeding behavior of the Tawny-throated Dotterelbreeding pairs during the spring to proceed with nest searches, systematically inspecting the vegetative strata where nests could occur [18]. When a nest was located, a MOULTRIE™ Edge solar cellular camera trap (Moultrie manufacturer, Birmingham, Alabama, USA) was deployed 1.8–2.3 m away from the nest to quantify the frequency of parental attention to the nest [19]. This frequency was used to monitor nesting parameters and daily nest care behavior [19]. The camera remained active during the entire breeding period from 1 October to 29 December 2025, capturing photographs every 60 min during the day and at night. To avoid pseudo-replication, we considered only the movements recorded at 1 h intervals throughout the study period, resulting in a sample set of 2160 photographs.

Using this methodology, we quantified the total time a parent spent at the nest, including the hour and day. For this task, we classified behavior into three behavioral classes: 1. incubating or guarding eggs, 2. temporary nest absence [when the parent bird did not appear in the photograph], and 3. other activities, such as vigilance close to the nest [without incubating or guarding]. Relative frequency, measured in terms of the proportion of each behavior, was estimated by dividing the total number of photographs of each behavior by the total number of photos obtained at a given time of day. Because behavioral classifications were based on still photographs collected at hourly intervals, the actual activity of the adult outside the camera’s field of view could not always be determined. Therefore, categories such as “temporary nest absence” refer operationally to the temporary absence of the adult from the photographed nest area and may also include foraging activities, vigilance outside the camera range, or other short-term movements.

3. Results

A total of 2160 photographs were included in the analysis during the study period. Incubation extended from early October to early December, during which the incubating adult remained on the nest, incubating the eggs, with daily presence primarily at dusk and night, while surveillance activities near the nest were most frequent in the afternoon. The sex of the incubating adult could not be determined from the camera-trap photographs; therefore, all observations are reported generically as referring to the adult or parental bird.

In the study area, we found only one nest. The nest measured approximately 39 × 22 mm and consisted of a shallow depression on the ground lined with plant material. The eggs were brownish in coloration, with dark mottled markings distributed across the shell surface.

The nest contained four eggs located in a small crevice predominantly covered by Cistanthe longiscapa. However, the nest itself was primarily composed of plant debris (Figure 2). It was found camouflaged within a dense floral cover consisting of C. longiscapa, which serves as a reproductive niche during this desert phenomenon.

For the monitored nest, the highest within-day frequency of incubation was recorded between 20:00 h. and the early hours of dawn, with a maximum frequency of 0.98, whereas the greatest vigilance frequency was recorded in the late afternoon, reaching its peak at 17:00 (0.96). Temporary nest absence during parental provisioning, representing the highest frequency, occurred at 14:00 (0.084) (Figure 3). When the camera was removed in December, the eggs had already hatched. However, subsequent fledging was not monitored. Therefore, the overall breeding success of the nesting attempt could not be determined. The camera did not record any predators during the monitoring period.

4. Discussion

In this study, we report, for the first time, nesting of Tawny-throated Dotterel in the flowering-desert ecosystem of the Atacama Desert, northern Chile, with the observed birds tentatively assigned to the Southern Population described by Jaramillo [11] for Chile. Previous information on the nesting of this species in the Atacama indicated that it occurred on the coast of Huasco [10,13,20], on Isla Chañaral and in Caleta Chañaral [21], and in Caserones [28°10′ S/69°32′ W] to the east of Tierra Amarilla, Copiapó, at 4300 m a.s.l., corresponding to the Northern Population indicated by Jaramillo [11]. These results align with reported nesting dates for this species in South American ecosystems [8,14,15,22], where austral spring appears to be the time window selected by the species for egg laying. The nest found here with eggs in early October is consistent with previous records for the Atacama Region, with chicks observed during November/December on Isla Chañaral and in Caleta Chañaral [21]. However, southern populations living in the Atacama Desert [Huasco] can nest during the end of winter and in the September period [13,20]. These differences between the breeding chronology observed in our study and that noted in previous reports from the south of the Atacama Region may indicate temporal variation in reproductive activity among localities or years. In particular, records of chicks during August and September could be consistent with nesting occurring earlier in the season, potentially during the end of winter.

The nest structure found in this area, built from plant debris in our study, has been previously described in regard to the Charadriidae family as an adaptation that camouflages nests from potential predators such as reptiles and raptors [22,23]. Furthermore, the high frequency of movement for the incubating adult, presumably associated with vigilance (movement was highest in the afternoon), is primarily linked to Charadriidae behavior during the breeding season. In this context, other family members, such as the Red-wattled Lapwing (Vanellus indicus), employ mobbing or circling of a nest to deter potential predators [24]. Although we obtained photographs of the parent walking near the nest, we inferred that the bird exhibited distractive behaviors to protect the nest. Previous investigations of the family Charadriidae indicate that the distraction patterns of the incubating adult, intended to deter potential egg predators, consist of circling around the nest or even brief departures for short periods [25]. Regarding temporary nest absence, these events occurred predominantly during the day, presumably to allow parental feeding, given that the Tawny-throated Dotterel’s diet is mainly composed of diurnal prey items such as beetles and larvae [22]. Despite the value of this record, the scope of our findings is limited because the observations were obtained from a single nesting event monitored with one camera trap. Therefore, our results should be regarded as documenting the occurrence of breeding at the study site rather than demonstrating that the area constitutes a regular nesting ground for the Tawny-throated Dotterel. Further research based on multiple nesting records and extensive monitoring efforts must be conducted to improve our understanding of the species’ breeding ecology, nesting-site fidelity, and habitat requirements.

The development and installation of mining and energy projects on the stands of the flowering desert represent a new threat to this species since these projects involve installing industrial structures over extensive surfaces, with consequent destruction of and reductions in habitat for endemic species in the desert [26]. In addition, there is the threat posed by wind farms installed in the Atacama Desert in the last decade, sectors that include the species’ wintering areas, the repurposing of agriculture in central Chile toward an export-oriented model [12,27], and the rapid expansion of urban areas into rural zones [16,28].

5. Conclusions

This study documents an Tawny-throated Dotterel nesting event, providing evidence of reproductive activity in the area during the period surveyed. This observation contributes to our knowledge of the species’ breeding distribution and habitat use. However, because this study is based on a single nesting record, no conclusions can be drawn regarding the site’s importance as a recurrent breeding area, the effectiveness of the surrounding vegetation in reducing predation risk, or broader patterns in the species’ behavior. Continued monitoring and additional breeding records are required in order to better understand habitat selection, nesting success, and reproductive ecology in relation to this species.