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Monteiro's Storm-petrel  Hydrobates monteiroi
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This species is listed as Vulnerable as it has a very small population which is restricted to breeding on just two islets. It is therefore highly susceptible to stochastic events, and remains at risk of mammalian introductions and avian predators.

Taxonomic source(s)
Bolton, M.; Smith, A. L.; Gómez-Díaz, E.; Friesen, V. L.; Medeiros, R.; Bried, J.; Roscales, J. L.; Furness, R. W. 2008. Monteiro's Storm Petrel Oceanodroma monteiroi: a new species from the Azores. Ibis 150(4): 717-727.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Taxonomic note
Hydrobates monteiroi (del Hoyo and Collar 2014) was previously placed in the genus Oceanodroma. Oceanodroma castro (Sibley and Monroe 1990, 1993) was previously split into O. castro and O. monteiroi following Bolton et al. (2008).

Oceanodroma monteiroi Bolton, A.L. Smith, E. Gomez-Diaz, V.L. Friesen, R

Oceanodroma monteiroi is a medium-sized, stocky storm-petrel with quite broad wings and square tail. Feet do not project beyond tail in flight. The species has a more prominent diagonal wing bar than that of the Madeiran Storm-petrel O. castro (Robb & Mullarney 2008), although such wing markings in storm-petrels vary with age and season.

Distribution and population
Oceanodroma monteiroi breeds on two islets off the island of Graciosa in the Azores, Portugal. Breeding is suspected on further islets (including some stacks off Flores and Corvo island) in the Azores, but proof is still lacking (Bolton et al. 2008, J. Bried in litt. 2010).  It is thought to remain in the vicinity of the Azores during the non-breeding season, a suggestion which is supported by the analysis of carbon isotopes (Bolton et al. 2008). Although unlikely to occur eslewhere, identification amongst Madeiran Storm-petrel O. castro is difficult (W. Bourne in litt. 2012). The total population size was estimated at 250-300 pairs in 1999 (Bolton et al. 2008). Accounts from the 16th and 17th centuries of a small black and white seabird, which appear to match the breeding cycle of this species, indicate that it may have once been far more abundant (Bolton et al. 2008), however there are no recent trend data.

Population justification
The population was estimated at 300 pairs in 1999 (Bolton et al. 2008). Although this estimate is now a decade old, the population is not thought to have declined since, and may have actually increased, particularly in response to the installation of artificial nest boxes on Praia islet. Thus, the population is best placed in the band 250-999 mature individuals. This equates to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.

Trend justification
Although there is no trend data, the population is suspected to be stable in the absence of any known threats. The population may have even increased since the last known population estimate in 1999 owing to an increase in annual productivity following the installation of nest boxes (Bolton et al. 2008, Bried et al. 2009).

This species breeds during the 'hot season'; females lay eggs between early May (perhaps late April) and early July, incubating a single egg until as late as early August, with the first chicks hatching in early June and the latest chicks fledging in early October (Bolton et al. 2008). Its diet is poorly known, but thought to consist of small fish and squid, and it generally feeds on prey of a higher tropic level than O. castro (Bolton et al. 2008).

Threats include high predation rates by Long-eared Owls Asio otus that are resident in the Azores; up to 40 adults are killed in some seasons (Bolton et al. 2008). Both breeding islets are currently free of ground predators, but their close proximity to Graciosa and the large numbers of visitors to one islet in the summer means that the introduction of rodents is a continuing threat (Bolton et al. 2008). Both islets lie within 2 km of the main shipping route for large passenger ferries and container ships docking on Graciosa. A cargo ship containing livestock ran aground on one of the breeding islets in 2000, leading to concerns over pollution and rodents escaping ashore (Bolton et al. 2008).

Conservation Actions Underway
Both breeding islets are designated under European legislation as Special Protection Areas and are assigned a full-time warden based on Graciosa (Bolton et al. 2008). Recent work to reduce interspecific competition for nest cavities with rabbits and other larger procellariiform species through the installation of nest boxes has met with considerable success, leading to a large increase in annual productivity (Bolton et al. 2008). Nest boxes had higher productivity than natural nest sites, probably due to the greater degree of protection they provided from inclement weather and interspecific competition for nest space (Bried et al. 2009). Data from a MRR ringing study is being analysed, with preliminary results suggesting annual survival is high (F. Jiguet in litt. 2010). Conservation Actions Proposed
Obtain an up-to-date population census. Continue constructing artificial nest-sites. Consider (re-)introducing the species to other islets in the Azores, reducing the potential impact of rodents being introduced to one of the current breeding islets. Monitor the breeding islets for rodent introductions. Assess predation by other potential predators including gulls and reptiles (particularly Madeira Lizard Teira dugesii).

Related state of the world's birds case studies

Bolton, M.; Smith, A. L.; Gómez-Díaz, E.; Friesen, V. L.; Medeiros, R.; Bried, J.; Roscales, J. L.; Furness, R. W. 2008. Monteiro's Storm Petrel Oceanodroma monteiroi: a new species from the Azores. Ibis 150(4): 717-727.

Bried, J.; Magalhães, M. C.; Bolton, M.; Neves, V. C.; Bell, E.; Pereira, J. C.; Aguiar, L.; Monteiro, L. R.; Santos, R. S. 2009. Seabird habitat restoration on Praia Islet, Azores Archipelago. Ecological Restoration 27(1): 27-36.

Robb, M.; Mullarney, K. 2008. Petrels night and day: a sound approach guide. The Sound Approach, Poole, U.K.

Robert, A., Paiva V. H., Bolton M., Jiguet F. and Bried J. In press. The interaction between reproductive cost and individual quality is mediated by oceanic conditions in a long-lived bird. Ecology.

Further web sources of information
Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Calvert, R., Derhé, M., Anderson, O. & Symes, A.

Bried, J., Jiguet, F., Bourne, W. & Robert, A.

Recommended citation
BirdLife International (2016) Species factsheet: Hydrobates monteiroi. Downloaded from on 28/10/2016. Recommended citation for factsheets for more than one species: BirdLife International (2016) IUCN Red List for birds. Downloaded from on 28/10/2016.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Vulnerable
Family Hydrobatidae (Northern Storm-petrels)
Species name author Bolton et al., 2008
Population size 250-999 mature individuals
Population trend Stable
Distribution size (breeding/resident) 737,000 km2
Country endemic? Yes
Links to further information
- Additional Information on this species
- 2015 European Red List assessment