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Ashy-faced owl

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Ashy-faced owl
Ashy-faced owl
CITES Appendix II (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Strigiformes
Family: Tytonidae
Genus: Tyto
Species:
T. glaucops
Binomial name
Tyto glaucops
(Kaup, 1852)

The ashy-faced owl (Tyto glaucops) is a species of bird in the barn-owl family Tytonidae. It is found on the Caribbean island of Hispaniola, on Dominica, and on several other islands of the Lesser Antilles.[3]

Taxonomy and systematics

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The ashy-faced owl was formally described in 1852 by the German naturalist Johann Jakob Kaup and given the binomial name Strix glaucops.[4] The specific epithet is from Ancient Greek glaukos meaning "blue-grey" or "glaucous".[5] Kaup specified the type locality as Jamaica. This was an error and has been corrected to Hispaniola.[6] The ashy-faced owl is now placed in the genus Tyto that was introduced in 1828 by Gustaf Johan Billberg.[3]

The taxonomy of the ashy-faced owl is unsettled. At one time it was considered conspecific with the barn owl sensu lato (Tyto alba).[7] After the separation the International Ornithological Committee (IOC) long treated it as monotypic but in July 2023 moved two subspecies from the American barn owl (Tyto furcata) into it.[3] The North American Classification Committee of the American Ornithological Society (AOS/NACC) and the Clements taxonomy retain it as monotypic.[8][9] In 2022 the AOS/NACC rejected a proposal to make that move.[10] BirdLife International's Handbook of the Birds of the World (HBW) has long treated the ashy-faced owl as having the three subspecies recognized by the IOC, and adds a fourth that the other three taxonomies do not recognize as part of any species.[11]

Subspecies

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This article follows the IOC treatment with these three subspecies:[3]

Description

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The ashy-faced owl is 27 to 33 cm (11 to 13 in) long. Males weigh about 260 to 350 g (9.2 to 12 oz) and females about 460 to 540 g (16 to 19 oz). Adults of the nominate subspecies T. g. glaucops on Hispaniola have a silvery gray facial disc. Their upperparts are dark grayish brown with paler and dusky vermiculation. Their wings have buff or tawny mottling and their underparts are tawny with some darker barring. They have light, dark, and intermediate morphs. Their iris is blackish brown, their bill yellowish horn, and their legs and feet grayish brown. The ashy-faced owl is generally described as having a mix of red and brown coloration, long thin legs, a heart-shaped face, and silver-grey feathers.[12] Juveniles are similar to adults with a darker gray face.[7]

Subspecies T. g. insularis has a vinaceous-brown facial disc. Its upperparts are blackish gray with sparse white spots and streaks. Its wings are darker than its upperparts and have tawny mottling and feather edges. Its underparts are cinnamon-buff with dusky mottling and a few white spots. Subspecies T. g. nigrescens is very similar to insularis but has almost no white on its upperparts and less mottling on its underparts.[13]

Distribution and habitat

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The nominate subspecies of the ashy-faced owl is found on the island of Hispaniola, which is shared by the Dominican Republic and Haiti, and on Île de la Tortue of the northwestern Haitian coast. T. g. insularis is found on the islands of St. Vincent, Bequia, Union, Carriacou, and Grenada in the southern Lesser Antilles. T. g. nigrescens is found on the island of Dominica in the north-central Lesser Antilles.[3][7][13]

On Hispaniola the ashy-faced owl inhabits a wide variety of landscapes, both natural and human-altered. The former include open woodlands, denser broadleaf forest, and scrublands. The latter includes farmlands, oil-palm plantations, solitary buildings, and villages and towns.Tyto glaucops is most often found in lowland areas, but can sometimes be found at higher elevations, such as foothills.[14] In elevation it ranges from sea level to 2,000 m (6,600 ft). They have a preference for habitats that have a balance between open spaces for hunting and enough canopy cover for nesting.[14] The ashy-faced owl is known for being solitary and territorial by nature. This requires them to inhabit large and undisturbed areas of land in order to maintain a stable population.[15] The other two subspecies also use essentially all available habitats on their small islands.[7][13]

Behavior

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Movement

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The ashy-faced owl is a year-round resident throughout its range, though on Hispaniola young may disperse quite widely from their natal site.[7][13]

Feeding

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The ashy-faced owl is primarily a nocturnal hunter, though in the absence of competing diurnal predators, some may hunt during the day. Its diet is mostly small vertebrates including mammals, birds, reptiles, and amphibians, but it also feeds on invertebrates.[7][13] A study published in 2010 compared the diets of ashy-faced and American barn owls (Tyto furcata pratincola) in the Dominican Republic. Barn owls had first arrived on Hispaniola around 1950. The author examined the regurgitated pellets the owls produce, which contain the undigested bones, fur, and feathers of their prey. It was found that they each consume over 100 species of prey, with 92 species being in common between the two. Small mammals predominated in both diets, particularly so in the American barn owl, and made up the greatest proportion of the biomass. Both caught a similar proportion of bats, but the ashy-faced owl caught more birds. Amphibians and reptiles were also consumed more often by the ashy-faced owl than by the American barn owl. The ashy-faced owl is shown to exhibit dietary competition with the invasive barn owl species, Tyto alba, which established itself in Hispaniola around the 1950s. This introduction led to a dietary overlap with the ashy faced owl population. This has led to competition and implications for resource partitioning and effects on the ecological niche stability of the ashy-faced owl.[16] No conclusion could be reached as to whether the competition for food caused by the arrival of the American barn owl was detrimental to the native species.[16]

Breeding

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The nominate subspecies of the ashy-faced owl on Hispaniola breeds mostly between January and June. Eggs of T. g. nigrescens have been reported in September and nestlings in April. There are no data specific to the breeding season of T. g. insularis. The ashy-faced owl nests in cavities, both natural and human-made. Natural holes in tree trunks and branches, the walls of sinkholes, earthen banks, and cliffs are used. The ashy-faced owl has been shown to exhibit behaviors of using existing nests of other bird species such as the endemic Palmchat (Dulus dominicus). This nesting choice is atypical for the Tytonidae family, displaying an opportunistic style of nest site selection. Opportunistic nesting demonstrates a flexibility in their nesting ecology, which is advantageous considering the limited habitat space on Hispaniola and its neighboring islands.[17] The species also nests in human structures such as barns, church steeples, abandoned buildings, nest boxes provided for them, and even the attics of occupied dwellings.[7][13] Ashy-faced owls have a preference for nests in secluded areas, including tree cavities and abandoned nests. These nesting choices seem to relate to decreased predation and increased fledgling survival .[18]

Dickcissel male perched on a metal pole singing, with neck stretched and beak open.

Songs and calls
Listen to ashy-faced owl (Hispaniola) on xeno-canto

Vocalization

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On Hispaniola the ashy-faced owl makes a "hissing cry, prefaced by a series of higher-pitched ratchety clicks and a c. 2–3 seconds screeching call likened to criiisssssh.[7] Other vocalizations of the nominate subspecies and those of the other two subspecies have not been well studied, but anecdotally include a wide variety of "screeches, wheezes, purrs, snores, twitters, hisses and yelps".[7][13]

Ecological Significance

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The ashy-faced owl serves an ecological role as a nocturnal predator, helping to maintain the population of rodent species. Through their predatory behaviors, they serve an essential role in maintaining environmental balance in forests and agricultural ecosystems by curbing the small mammal populations.[15]

Status

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The IUCN has assessed the ashy-face owl as being of Least Concern. Though it has a somewhat limited range and its population size is not known, the latter is believed to be stable. No immediate threats have been identified.[1] The species is "[w]idespread and locally common on Hispaniola". The "[s]tatus of Lesser Antillean subspecies [is] insufficiently known, but nigrescens appears to be common on Dominica, whereas insularis is rare on St Vincent and Grenada and in Grenadines, and might be vulnerable to habitat destruction and pesticide usage."[13]

References

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  1. ^ a b BirdLife International (2016). "Ashy-faced Owl Tyto glaucops". IUCN Red List of Threatened Species. 2016: e.T22688511A93199076. doi:10.2305/IUCN.UK.2016-3.RLTS.T22688511A93199076.en. Retrieved 12 August 2023.
  2. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. ^ a b c d e Gill, F.; Donsker, D.; Rasmussen, P., eds. (July 2023). "Owls". IOC World Bird List. v 13.2. Retrieved July 31, 2023.
  4. ^ Kaup, Johann Jakob (1852). "Monograph of the owls (Strigidae)". Contributions to Ornithology for 1852. 5: 103–122 [118].
  5. ^ Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. p. 174. ISBN 978-1-4081-2501-4.
  6. ^ Peters, James Lee, ed. (1940). Check-List of Birds of the World. Vol. 4. Cambridge, Massachusetts: Harvard University Press. p. 81.
  7. ^ a b c d e f g h i Bruce, M.D., G. M. Kirwan, and J. S. Marks (2020). Ashy-faced Owl (Tyto glaucops), version 1.0. In Birds of the World (S. M. Billerman, B. K. Keeney, P. G. Rodewald, and T. S. Schulenberg, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.asfowl1.01 retrieved August 12, 2023
  8. ^ Chesser, R. T., S. M. Billerman, K. J. Burns, C. Cicero, J. L. Dunn, B. E. Hernández-Baños, R. A. Jiménez, A. W. Kratter, N. A. Mason, P. C. Rasmussen, J. V. Remsen, Jr., and K. Winker. 2023. Check-list of North American Birds (online). American Ornithological Society. https://checklist.americanornithology.org/taxa/
  9. ^ Clements, J. F., T. S. Schulenberg, M. J. Iliff, T. A. Fredericks, J. A. Gerbracht, D. Lepage, S. M. Billerman, B. L. Sullivan, and C. L. Wood. 2022. The eBird/Clements checklist of birds of the world: v2022. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/ retrieved November 10, 2022
  10. ^ R. Terry Chesser, Shawn M. Billerman, Kevin J. Burns, Carla Cicero, Jon L. Dunn, Blanca E. Hernández-Baños, Rosa Alicia Jiménez, Andrew W. Kratter, Nicholas A. Mason, Pamela C. Rasmussen, J. V. Remsen, Jr., Douglas F. Stotz, and Kevin Winker. "Sixty-third supplement to the American Ornithological Society’s Check-list of North American Birds". American Ornithology 2022, vol. 139:1-13 retrieved August 9, 2022
  11. ^ HBW and BirdLife International (2022) Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 7. Available at: https://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v7_Dec22.zip retrieved December 13, 2022
  12. ^ Raffaele, HA (1998). "A guide to the birds of the West Indies". Choice Reviews Online. 36 (04): 36–2175. doi:10.5860/choice.36-2175.
  13. ^ a b c d e f g h Marti, C. D., A. F. Poole, L. R. Bevier, M.D. Bruce, D. A. Christie, G. M. Kirwan, and J. S. Marks (2020). Barn Owl (Tyto alba), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.brnowl.01 retrieved August 12, 2023
  14. ^ a b Bond, J. (1928). "The distribution and habits of the birds of the Republic of Haiti". Proceedings of the Academy of Natural Sciences of Philadelphia. 80: 483–521. doi:10.2307/4064003.
  15. ^ a b Thorstrom, R.; Gallardo, JC (2017). "The owls of Hispaniola and Puerto Rico". Springer eBooks. Springer. pp. 517–534. doi:10.1007/978-3-319-57108-9_14.
  16. ^ a b Wiley, James W. (2010). "Food Habits of the Endemic Ashy-Faced Owl (Tyto glaucops) and Recently Arrived Barn Owl (T. alba) in Hispaniola". Journal of Raptor Research. 44 (2): 87–100. doi:10.3356/JRR-08-100.1. S2CID 54542646.
  17. ^ Curti, M.; Hayes, CD; Hayes, TI; Calcaño Silven, M. (2018). "First description of Ashy-faced Owl (Tyto glaucops) nest and first record of Ashy-faced Owl nesting in Palmchat (Dulus dominicus) nest on Hispaniola". Journal of Caribbean Ornithology. 31: 17–19.
  18. ^ Townsend, JM; Rimmer, CC; Latta, SC; Mejia, D; Garrido, EG; McFarland, KP (2018). "Nesting ecology and nesting success of resident and endemic tropical birds in the Dominican Republic". The Wilson Journal of Ornithology. 130 (4): 849. doi:10.1676/17-078.
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