Hornby's Storm Petrel Oceanodroma hornbyi is an ende -
mic species of the Humboldt Current Region, regularly
observed at distances between 30 and 500 km off the
southern coasts of Ecuador, Peru and northern Chile
(Murphy 1936, Spear & Ainley 2007). During the
southern spring, the species is concentrated off the
southern coast of Ecuador and northern Peru, and in
the autumn off the southern coast of Peru and northern
Chile (Spear & Ainley 2007).
The population has been estimated at between
1000 and 90,000 individuals (Brooke 2004, Birdlife
International 2016). However, Spear & Ainley (2007)
calculated the abundance of this species through tran-
sects on open sea, estimating populations of 637,200
individuals in the southern spring and 1,011,900 indi-
viduals in autumn. This uncertainty as to their popula-
tion size could be solved by locating their breeding
colonies and estimating their sizes (Carboneras &
Bonan 2017), although that estimation would not
include the non-breeding population. In any case,
locating the colonies is an important step to assess the
vulnerability of the species and to protect it if neces-
Hornby's Storm Petrel is one of the last species of
seabirds whose breeding sites remain unknown. This is
one of the main reasons why it has been classified as
‘Data Deficient’ on the IUCN Red List (Birdlife Inter -
national 2016). Therefore, finding and characterizing
First breeding site record of Hornby’s Storm Petrel
Oceanodroma hornbyi in the Atacama Desert, Chile
Rodrigo Barros1,*, Fernando Medrano1,2,*, Rodrigo Silva1& Felipe de Groote1
Barros R., Medrano F., Silva R. & de Groote F. 2018. First breeding site record of
Hornby’s Storm Petrel Oceanodroma hornbyi in the Atacama Desert, Chile.
Ardea 106: 203–207. doi:10.5253/arde.v106i2.a2
Hornby’s Storm Petrel Oceanodroma hornbyi is endemic to the Humboldt
Current Region. Historically, little has been known about the location of the
species’ breeding sites or the size of its population. For these reasons, this
species has been classified as ‘Data Deficient’ by IUCN, and it is difficult to know
whether the species is threatened, and if so, what conservation actions may be
necessary. As part of the project ‘Golondrinas del Desierto’ a search for the
colonies of this species began in November 2013. It was known that the species
breeds in the Atacama Desert, because some mummified individuals had been
found there, and fledglings attracted by lights whilst on their way to the sea were
found in nearby coastal cities. In this paper, we describe the first breeding site
discovered for this species. This breeding location is 75 km from the shoreline,
at 1100 meters above sea level, in the centre of the Atacama Desert, also known
as the ‘absolute desert’. However, there is strong anthropogenic pressure on this
desert due to the development of mines and solar energy projects. To protect
these birds, it is important to estimate the breeding population size of the colony,
search for new colonies and assess the threats to each of them, and to evaluate
how many fledglings are drawn off course by lights into cities and industrial sites
and how many die there.
Key words: Hornby’s Storm Petrel, Ringed Storm Petrel, data deficient, seabird,
1Red de Observadores de Aves y Vida Silvestre de Chile (ROC); 2Instituto de
Ecología y Biodiversidad. Departamento de Ciencias Ecológicas. Facultad de
Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile;
*corresponding authors (email@example.com,
ARDEA 106(2), 2018
their reproductive colonies is a priority to enable an
adequate assessment of their conservation status
(Drucker & Jaramillo 2013).
A dead adult and juvenile were found in a cavity in
1894 in Taltal, in the Antofagasta region (Philippi
1895); a mummified specimen was discovered in 1923
in a nitrate mine near the Santa Luisa Office, about 50
km from the coast at 1600 meters above sea level,
inland of Taltal (Stresemann 1924). Mummies were
also found in nitrate deposits in Pampa del Toco, in the
interior of Tocopilla, Antofagasta region, and in the Loa
river basin, on the border between the regions of
Tarapacá and Antofagasta (Wetzel 1925). These discov-
eries served as the basis for the early hypothesis that
the species breeds in the Atacama Desert (Hellmayr
1932, Murphy 1936, Goodall et al. 1951).
This idea has been reinforced by the discovery of
adults and fledglings attracted to lights in desert areas
of southern Peru: Huarmey, Lima, Lunahuana, Arequipa,
Moquegua, Ite and Tacna (Koepcke 1964, Drucker &
Jaramillo 2013, Murillo et al. 2013, eBird 2017,
Jhonson Vizcarra pers. obs.), and of northern Chile:
Arica, Iquique, Tocopilla, Michilla, Mejillones, Anto -
fagasta, Baquedano, Sierra Gorda and La Negra
(Brooke 2000, Brooke 2004, Gómez 2012, eBird 2017,
and pers. obs. by Ronny Peredo, Vinko Malinarich,
Verónica González, Bárbara Olmedo, and Silvia
Hernández). Also, there are some records at high alti-
tudes in Cordillera Blanca, department of Ancash, Peru:
one at 2225 m a.s.l. in Caraz, another at 3800 m a.s.l.
in the Jangas district (Drucker & Jaramillo 2013,
Murillo et al. 2013) and at 3150 m a.s.l. in Huaraz
(eBird 2017, checklist S13767880), which suggests
that there may also be breeding sites at high altitudes.
Brooke (2000, 2004) assumed that the nesting
period is between March and July, since most of the
Trinidad and Tobago
locations with mumified birds
locations with fledglings
breeding colony found in this study
Oficina Santa Luisa
Inland of Taltal
80°50'W 78°0'W 75°10'W 72°20'W 69°30'W 66°40'W
Figure 1. Map of inland records of Hornby’s Storm Petrel in Chile and Peru, with the location of the first breeding site found in this
fledglings attracted by lights are found between June
and July. However, Spear & Ainley (2007) reported a
female with an enlarged follicle in late November,
suggesting that egg laying could start in December. The
latter is consistent with the analysis of wing moult in
adults, which suggests a reproductive season between
January and June (Howell 2012).
With the objective of taking the first step towards
increasing the knowledge of the breeding ecology of
this bird, needed to assess the conservation status of
the species, we organised field trips in the Atacama
Desert, searching for breeding locations of the Hornby’s
Between 2013 and 2017, a team of volunteers from
Red de Observadores de Aves y Vida Silvestre de Chile
(ROC) surveyed 780 linear km of the Atacama Desert
in northern Chile, mainly searching for breeding sites of
Markham’s Storm Petrel Oceanodroma markhami
(Schmitt et al. 2016). This process allowed us to create
a clear search image that laid the foundations for the
discovery of the breeding location that we report here,
since both species breed in similar cavities (but
Hornby’s Storm Petrel breeds in gypsum cavities, while
Markham’s Storm Petrel breeds in salt-made cavities).
In December 2016, we surveyed the area of Pampa
de Indio Muerto (26.204°S, 69.919°W), 20 km north of
the city of Diego de Almagro in the Atacama Region,
where we found natural shallow cavities with petrel
odour and white and grey feathers inside. Although all
the cavities were natural, sometimes they showed signs
of active digging by petrels, who probably enhance the
cavities to make them suitable for breeding. When we
analysed the collected feathers (a wing feather and
some body feathers), they coincided in size, colour and
shape with a mummified specimen found earlier.
Between 1 and 3 April 2017, a team of four people
visited the Pampa de Indio Muerto again, surveying an
area of approximately 64 ha, 25 cavities were found
with the same odour, some with remains of feathers
inside, confirming the site as a breeding location of
petrels (Figure 1). During the two nights that the team
remained at the site, no vocalizations of petrels were
heard. To verify which species was breeding, 50 × 50
cm mist nets were installed in the mouth of some cavi-
ties for two nights (four nets the first night and 10 nets
the second night).
Results and Discussion
On the second night of mist netting at potential nests
(2 April 2017), an adult specimen of Hornby’s Storm
Petrel was captured leaving the burrow at 6:00 am,
which confirmed the first nest ever found for this
species (Figures 2A and 2B). The breeding location is
situated at 1100 m a.s.l. and 75 km in a straight line
from the coastline, located in what is known as the
‘absolute desert’ (Luebert & Pliscoff 2006). The area
consists of an extensive pampa formed by a hillock of
soil substrate, crossed by dry runoff streams (Figure
2C). The cavities were situated in low-slope hills since
the flat areas are occasionally washed by landslides.
The cavities were located in outcrops of gypsum, where
there are natural cavities of unknown depths. The
surveyed area is a minor part of a large area with relief
and homogeneous substrate, so the breeding area could
be much larger.
Following the discovery of this breeding location,
potential threats were identified, such as development
of mining and solar energy projects in the Atacama
Desert, which could directly affect areas with nests, and
incidental effects of artificial light on fledglings. These
threats could be present both in the vicinity of the
breeding location and on their flight routes to the sea.
This discovery will help orient future search efforts
which should focus on locating and characterizing new
breeding locations of Hornby’s Storm Petrel, as well as
increasing knowledge of the species’ natural history,
reproductive biology, population size and potential
threats. For locating new breeding sites, it would be
possible to use miniaturized radio telemetry, as was
used by Rayner et al. (2015) to search for New Zealand
Storm Petrels Fregetta maoriana (which are smaller
than Hornby’s Storm Petrels; an advantage in using
these devices). To attract the birds in order to catch
them on land, a combination of lights and call playback
could be used (Ismar et al. 2015), although this would
first require the recording of a Hornby’s Storm Petrel’s
call. Also, efforts to assess the colony size are needed,
since we surveyed only 25 nests in two days, but the
breeding site is probably more extensive. For this
purpose, transect counts can be used, as has been done
for Markham’s Storm Petrel (Rodrigo Barros, unpubl.
data). Another priority is assessing how many fledg-
lings are drawn off course by lights into cities and
industrial sites, and how many die there, to evaluate if
measures should be taken to prevent this. The re-evalu-
ation of the species’ conservation category based on
adequate information (both in Chile as elsewhere), the
effective protection of colonies and making an inven-
tory of potential threats are fundamental steps for the
conservation of the species, objectives that should be
our goal in the short term.
ARDEA 106(2), 2018
BirdLife International 2016. Hydrobates hornbyi. The IUCN Red
List of Threatened Species 2016: e.T22698567A93690126.
3.RLTS.T22698567A93690126.en (accessed 31 October
Brooke M. 2000. Report on a project supported by a BOU
research grant. Ibis 142: 348–349.
Brooke M. 2004. Albatrosses and petrels across the World.
Oxford University Press, Oxford, UK, and New York, USA.
Carboneras C. & Bonan A. 2017. Northern Storm-petrels
(Hydrobatidae). In: del Hoyo J., Elliott A., Sargatal J.,
Christie D.A. & de Juana E. (eds) Handbook of the birds of
the world alive. Lynx Edicions, Barcelona.
Figure 2. (A) Hornby’s Storm Petrel captured using mist nets. (B) Cavity where the bird was caught. (C) Habitat where the breeding
colony of Hornby’s Storm Petrel is located (Pampa de Indio Muerto, Atacama Region, Chile, April 2017).
We are grateful to Jhonson Vizcarra, Ronny Peredo, Vinko
Malinarich (SAG Tarapacá), Verónica González, Bárbara
Olmedo and Silvia Hernández (Fundación para la Susten -
tabilidad del Gaviotín Chico) for their databases with data on
rescued Storm Petrels in their study areas and to Ivo Tejeda for
assistance in the field and for technical support. Also, to Derek
Carne and Sarah Gilman for their help with the English transla-
tion. We thank the American Bird Conservancy, especially
Hannah Nevins and Brad Keitt, who granted and supported the
Desert Storm Petrels project. Finally, we are very grateful to
Michael Brooke, Tamar Lok and Stephanie Ismar, who signifi-
cantly improved this manuscript with their comments. This rese-
arch was conducted according the Chilean law, which regulates
the scientific capture of birds, under the permission N°
Short notes 207
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droma hornbyi), version 1.0. In: Schulenberg T.S. (ed.)
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NY, USA. doi.org/10.2173/nb.rispet1.01
eBird 2017. eBird: An online database of bird distribution and
abundance. Cornell Lab of Ornithology, Ithaca, NY.
Gómez G. 2012. Relación entre la presencia de la golondrina de
mar de collar, Oceanodroma hornbyi (Procellariiformes;
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norte de Chile, región de Antofagasta. Undergraduate
thesis, Universidad de Antofagasta, Antofagasta.
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Chile su conocimiento y sus costumbres. Tomo Segundo.
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Hellmayr C.E. 1932. The birds of Chile. Zoological Series,
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A.J. & Rayner M.J. 2015. Evaluating on-land capture
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Het Gekraagd Stormvogeltje Oceanodroma hornbyi is een ende-
mische soort van het zeegebied van de Humboldtstroom langs
de westkust van Zuid-Amerika. Er is nagenoeg niets bekend
over de ligging van de broedplaatsen en de grootte van de popu-
latie, zoals ook blijkt uit de classificatie van de status van de
soort door IUCN (‘Data Deficient’). Het is onbekend of de soort
wordt bedreigd en als dat het geval is, welke beschermingsmaat-
regelen er nodig zouden zijn voor het behoud van de soort. Als
onderdeel van het project ‘Golondrinas del Desierto’ begon in
november 2013 in Chili een zoektocht naar kolonies van het
Gekraagd Stormvogeltje. Het was bekend dat deze in de
Atacama-woestijn broedt, omdat daar ooit gemummificeerde
vogels waren gevonden en er in nabijgelegen kustplaatsen
uitgevlogen jongen waren gevonden, die waren aangetrokken
door het kunstlicht toen ze op weg waren naar zee. In dit artikel
beschrijven we de ontdekking van de eerste broedplaats van de
soort. De broedlocatie ligt op 75 km van de kust, op 1100 meter
boven de zeespiegel, in het midden van de Atacama-woestijn
(de droogste plaats op Aarde). Er is echter een sterke antropo-
gene druk op deze woestijn als gevolg van mijnbouw- en zonne-
energieprojecten. Om de vogels te beschermen is het belangrijk
om de populatiegrootte van de kolonie te bepalen, nieuwe kolo-
nies trachten te vinden en de bedreigingen voor elk daarvan in
kaart te brengen. Ook moet onderzocht worden hoeveel jonge
vogels worden aangetrokken door kunstlicht van steden en
industrieterreinen en hoeveel vogels daardoor omkomen.
Corresponding editor: Tamar Lok
Received 22 January 2018; accepted 25 April 2018