The Mariana crow (Corvus kubaryi) (Chamorro name: åga) is a species of the crow family from the tropical Western Pacific. It is a glossy black bird about 15 inches (38 cm) long and known only from the islands of Guam and Rota.
It is a rare bird which has steadily declined in numbers since the 1960s.[2] On Guam there are no remaining native Mariana Crows, the population having been decimated by the introduction of the brown tree snake.[3] On Rota the population has declined to less than 200 individuals,[4] the main threats here being the reduction of suitable habitat because of development and predation. Despite translocations from Rota to the Guam National Wildlife Refuge in the late 1990's and early 2000's, by 2011 the Mariana Crow was extirpated from Guam.[5] Current conservation efforts on Rota include habitat protection,[6] and a captive rear-and-release program.[7] The International Union for Conservation of Nature has rated the bird as being "critically endangered".
The Mariana crow is a small black crow with a bluish-black gloss on its tail, and a greenish-black gloss on its back, underparts, head, and wings. In general, females are smaller than males. An adult weighs about 9 ounces (260 g) and is about 15 inches (38 cm) long.[8]
The Mariana crow has a variety of vocalizations, including two locational calls used to maintain contact between pairs, family members and flock mates. These locational calls are either a high-pitched series of one to three caw or hi sounds, or a series of longer caw sounds with a nasal aaa element to the call; the latter call may be used exclusively between mated pairs. Alarm calls are a rapid series of sharp caws. The birds also make a variety of squalling, guttural sounds, which may be done either quietly or excitedly.[9]
Distribution and ecologyEdit
The Mariana crow inhabits second growth and mature forests, as well as coastal strand vegetation, but nests only in native limestone forest. It preferentially nests in the crowns of two canopy-emergent tree species: yoga tree (Elaeocarpus joga) and the figFicus prolixa.[2] The crow used to be distributed throughout the forested regions of Guam and Rota. It disappeared from southern Guam in the 1960s and from central Guam in the 1970s, mostly inhabiting Andersen Air Force Base. Its population on Rota has also decreased.[10]: 5–6
The Mariana crow begins nesting as early as July and as late as May. The nest is a large, cupped platform of small sticks, lined with leaf fibers. Clutch size varies from 1 to 4 eggs, and both parents incubate the eggs, brood the chicks, and care for the juveniles even after they fledge. Parental care has been known to range from 5 to 18 months, and juveniles may take as long as 3 years before entering the adult breeding cycle.[11]
Status and conservationEdit
On Guam, the Mariana crow's decline is primarily due to predation by the introduced brown tree snake (Boiga irregularis). In spite of protection of nesting-sites by electrical tree barriers, the remaining birds are considered to be reproductively senescent. On Rota, many other threats endanger the crow, including homestead development, resort and golf-course construction, agricultural settlement, nest-predation from introduced rats, the Mariana monitor lizard (Varanus tsukamotoi), typhoons, predation from feral cats, disease, and competition with the black drongo (Dicrurus macrocercus). More recently, the brown tree snake has also been detected on Rota, likely leading to serious declines in the Mariana crow population there if the snake population establishes itself. The Mariana crow is also persecuted by residents of both islands who see it as an obstacle to development.[12]
In 1993, a National Wildlife Refuge was established on Guam to preserve the remaining forest, and birds were translocated from Rota. Biologically controlling the brown tree snake is also being discussed.
Crows were transported from Rota to Guam in 2003 to assist conservation efforts though this may have had the unintended side effect of decreasing genetic variation within the species as tests have shown the Rota population is less diverse than the Guam.[8]
Formerly classified as an endangered species by the IUCN,[1] it was suspected to be rarer than generally assumed. Following the evaluation of its status, this was found to be correct, and it is consequently uplisted to critically endangered status in 2008 as it is in immediate danger of extinction, numbering so few birds that it could be entirely wiped out by a single catastrophic event such as an epidemic of West Nile virus.[12][13]
ReferencesEdit
^ abBirdLife International (2018). "Corvus kubaryi". IUCN Red List of Threatened Species. 2018: e.T22705959A129626293. doi:10.2305/IUCN.UK.2018-2.RLTS.T22705959A129626293.en. Retrieved 12 November 2021.
^ abc"Threatened and Endangered Animals in the Pacific Islands". U.S. Fish and Wildlife Service (USFWS). 20 September 2012. Retrieved 17 December 2015.
^Draft Revised Recovery Plan for the Aga or Mariana Crow (Corvus kubaryi) (Report). Portland, Oregon: U.S. Fish and Wildlife Service. 2005. Retrieved 1 February 2023.
^Kroner, Andria; Ha, Renee Robinette (September 2018). "An update of the breeding population status of the critically endangered Mariana Crow Corvus kubaryi on Rota, Northern Mariana Islands 2013–2014". Bird Conservation International. 28 (3): 416–422. doi:10.1017/S0959270917000053. ISSN 0959-2709. S2CID 90635351.
^Cortes-Rodriguez, Nandadevi; Campana, Michael; Berry, Lainie; Faegre, Sarah; Derrickson, Scott; Ha, Renee; Dikow, Rebecca; Rutz, Christian; Fleischer, Robert (1 March 2019). "Population Genomics and Structure of the Critically Endangered Mariana Crow (Corvus kubaryi)". Genes. 10 (3): 187. doi:10.3390/genes10030187. ISSN 2073-4425. PMC6471520. PMID 30832245.
^"CNMI DLNR Division of Fish & Wildlife". www.dfwcnmi.com. Retrieved 2 February 2023.
^"Endangered Mariana Crows Return to Island Forest". San Diego Zoo Wildlife Alliance. 8 October 2018. Retrieved 2 February 2023.
^ abJohn M. Marzluff; Tony Angell (2007). In the Company of Crows and Ravens. Yale University Press. ISBN978-0-300-12255-8.
^ Tomback, Diane F. (1986). "Observations on the behavior and ecology of the Mariana Crow" (PDF). The Condor. 88 (3): 398–401. doi:10.2307/1368898. JSTOR 1368898.
^National Research Council Staff (1997). The Scientific Bases for Preservation of the Mariana Crow. National Academies Press. ISBN978-0-309-05581-9.
^Morton, John; Plentovich, Sheldon; Sharp, Thomas (1999). Reproduction and juvenile dispersal of Mariana Crows on Rota 1996-1999 (Report). Retrieved 1 February 2023.
^ ab"Mariana crow species factsheet". BirdLife International (BLI). 2008. Retrieved 23 May 2008.
^. BirdLife International (BLI). 2008. Archived from the original on 14 September 2008. Retrieved 23 May 2008.
Wikispecies has information related to Mariana crow.
August 28, 2023
mariana, crow, corvus, kubaryi, chamorro, name, åga, species, crow, family, from, tropical, western, pacific, glossy, black, bird, about, inches, long, known, only, from, islands, guam, rota, conservation, statuscritically, endangered, iucn, scientific, classi. The Mariana crow Corvus kubaryi Chamorro name aga is a species of the crow family from the tropical Western Pacific It is a glossy black bird about 15 inches 38 cm long and known only from the islands of Guam and Rota Mariana crowConservation statusCritically Endangered IUCN 3 1 1 Scientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass AvesOrder PasseriformesFamily CorvidaeGenus CorvusSpecies C kubaryiBinomial nameCorvus kubaryiReichenow 1885It is a rare bird which has steadily declined in numbers since the 1960s 2 On Guam there are no remaining native Mariana Crows the population having been decimated by the introduction of the brown tree snake 3 On Rota the population has declined to less than 200 individuals 4 the main threats here being the reduction of suitable habitat because of development and predation Despite translocations from Rota to the Guam National Wildlife Refuge in the late 1990 s and early 2000 s by 2011 the Mariana Crow was extirpated from Guam 5 Current conservation efforts on Rota include habitat protection 6 and a captive rear and release program 7 The International Union for Conservation of Nature has rated the bird as being critically endangered Contents 1 Description 2 Distribution and ecology 2 1 Diet 2 2 Nesting 3 Status and conservation 4 ReferencesDescription EditThe Mariana crow is a small black crow with a bluish black gloss on its tail and a greenish black gloss on its back underparts head and wings In general females are smaller than males An adult weighs about 9 ounces 260 g and is about 15 inches 38 cm long 8 The Mariana crow has a variety of vocalizations including two locational calls used to maintain contact between pairs family members and flock mates These locational calls are either a high pitched series of one to three caw or hi sounds or a series of longer caw sounds with a nasal aaa element to the call the latter call may be used exclusively between mated pairs Alarm calls are a rapid series of sharp caws The birds also make a variety of squalling guttural sounds which may be done either quietly or excitedly 9 Distribution and ecology EditThe Mariana crow inhabits second growth and mature forests as well as coastal strand vegetation but nests only in native limestone forest It preferentially nests in the crowns of two canopy emergent tree species yoga tree Elaeocarpus joga and the fig Ficus prolixa 2 The crow used to be distributed throughout the forested regions of Guam and Rota It disappeared from southern Guam in the 1960s and from central Guam in the 1970s mostly inhabiting Andersen Air Force Base Its population on Rota has also decreased 10 5 6 Diet Edit Extremely versatile the Mariana crow is an opportunistic omnivore feeding on insects lizards other birds eggs hermit crabs fruits and seeds 2 Nesting Edit The Mariana crow begins nesting as early as July and as late as May The nest is a large cupped platform of small sticks lined with leaf fibers Clutch size varies from 1 to 4 eggs and both parents incubate the eggs brood the chicks and care for the juveniles even after they fledge Parental care has been known to range from 5 to 18 months and juveniles may take as long as 3 years before entering the adult breeding cycle 11 Status and conservation EditOn Guam the Mariana crow s decline is primarily due to predation by the introduced brown tree snake Boiga irregularis In spite of protection of nesting sites by electrical tree barriers the remaining birds are considered to be reproductively senescent On Rota many other threats endanger the crow including homestead development resort and golf course construction agricultural settlement nest predation from introduced rats the Mariana monitor lizard Varanus tsukamotoi typhoons predation from feral cats disease and competition with the black drongo Dicrurus macrocercus More recently the brown tree snake has also been detected on Rota likely leading to serious declines in the Mariana crow population there if the snake population establishes itself The Mariana crow is also persecuted by residents of both islands who see it as an obstacle to development 12 In 1993 a National Wildlife Refuge was established on Guam to preserve the remaining forest and birds were translocated from Rota Biologically controlling the brown tree snake is also being discussed Crows were transported from Rota to Guam in 2003 to assist conservation efforts though this may have had the unintended side effect of decreasing genetic variation within the species as tests have shown the Rota population is less diverse than the Guam 8 Formerly classified as an endangered species by the IUCN 1 it was suspected to be rarer than generally assumed Following the evaluation of its status this was found to be correct and it is consequently uplisted to critically endangered status in 2008 as it is in immediate danger of extinction numbering so few birds that it could be entirely wiped out by a single catastrophic event such as an epidemic of West Nile virus 12 13 References Edit a b BirdLife International 2018 Corvus kubaryi IUCN Red List of Threatened Species 2018 e T22705959A129626293 doi 10 2305 IUCN UK 2018 2 RLTS T22705959A129626293 en Retrieved 12 November 2021 a b c Threatened and Endangered Animals in the Pacific Islands U S Fish and Wildlife Service USFWS 20 September 2012 Retrieved 17 December 2015 Draft Revised Recovery Plan for the Aga or Mariana Crow Corvus kubaryi Report Portland Oregon U S Fish and Wildlife Service 2005 Retrieved 1 February 2023 Kroner Andria Ha Renee Robinette September 2018 An update of the breeding population status of the critically endangered Mariana Crow Corvus kubaryi on Rota Northern Mariana Islands 2013 2014 Bird Conservation International 28 3 416 422 doi 10 1017 S0959270917000053 ISSN 0959 2709 S2CID 90635351 Cortes Rodriguez Nandadevi Campana Michael Berry Lainie Faegre Sarah Derrickson Scott Ha Renee Dikow Rebecca Rutz Christian Fleischer Robert 1 March 2019 Population Genomics and Structure of the Critically Endangered Mariana Crow Corvus kubaryi Genes 10 3 187 doi 10 3390 genes10030187 ISSN 2073 4425 PMC 6471520 PMID 30832245 CNMI DLNR Division of Fish amp Wildlife www dfwcnmi com Retrieved 2 February 2023 Endangered Mariana Crows Return to Island Forest San Diego Zoo Wildlife Alliance 8 October 2018 Retrieved 2 February 2023 a b John M Marzluff Tony Angell 2007 In the Company of Crows and Ravens Yale University Press ISBN 978 0 300 12255 8 Tomback Diane F 1986 Observations on the behavior and ecology of the Mariana Crow PDF The Condor 88 3 398 401 doi 10 2307 1368898 JSTOR 1368898 National Research Council Staff 1997 The Scientific Bases for Preservation of the Mariana Crow National Academies Press ISBN 978 0 309 05581 9 Morton John Plentovich Sheldon Sharp Thomas 1999 Reproduction and juvenile dispersal of Mariana Crows on Rota 1996 1999 Report Retrieved 1 February 2023 a b Mariana crow species factsheet BirdLife International BLI 2008 Retrieved 23 May 2008 IUCN Redlist status changes BirdLife International BLI 2008 Archived from the original on 14 September 2008 Retrieved 23 May 2008 Wikispecies has information related to Mariana crow Retrieved from https en wikipedia org w index php title Mariana crow amp oldid 1171703999, wikipedia, wiki, book, books, library,
