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- The Worldwide Crow and Raven Appreciation Day, on April 27, celebrates one of many least-liked however most clever teams of birds round.
- In Sri Lanka, residence to 2 crow species, the birds are extensively seen as a nuisance — however one enabled by the continued follow of poor waste administration, which attracts crows in flocks of as much as 500.
- In “following the trash,” crows now happen even in wilderness havens resembling Horton Plains Nationwide Park, the place they feed on the trash left by human guests, in addition to on native wildlife species.
- Scientists finding out Sri Lanka’s crows say one of the best ways to get their inhabitants underneath management is thru higher administration of the nation’s waste, quite than the extra excessive choices of killing them or destroying their eggs.
COLOMBO — Crows have lengthy had a repute as a nuisance and a pest, regardless that it’s widely known that they’re among the many most clever of birds.
In Sri Lanka, that repute goes again some 2,000 years, to the Jataka morality tales from Buddhist custom. One of many tales tells of a “grasping crow” that spies a half-covered plate of fish in a nobleman’s kitchen and tries to steal it, solely to be caught, plucked and thrown out. The ethical being, in fact, that greed is unhealthy.
But when the modern-day crows of Sri Lanka are any indication, it will be secure to imagine that the Jataka crow ended up simply superb, ever hustling and thriving — the right avatar for the Worldwide Crow and Raven Appreciation Day that falls on April 27.
Sri Lanka is residence to 2 crow species: the large-billed crow (Corvus macrorhynchos) and the home crow (Corvus splendens), also called the Indian crow, a typical hen discovered all through a lot of South Asia. (The home crows present in Malaysia’s Penang state are thought to come back from a inhabitants of 56 birds introduced over from Sri Lanka within the Nineties for caterpillar management.)
Whereas the large-billed crow abounds in rural settings in Sri Lanka, the home crow happens principally in cities. One factor they’ve in widespread, although, is that each thrive on trash, flocking to the various open dumpsites across the island. One other factor: each are amongst simply seven hen species that aren’t protected underneath Sri Lankan legislation; the overwhelming majority of the round 500 hen species discovered within the nation are protected.
Thriving on trash
Colombo, Sri Lanka’s business capital, seems to have the nation’s largest crow inhabitants. The Discipline Ornithology Group of Sri Lanka (FOGSL), the native affiliate of BirdLife Worldwide, initiated a examine on Colombo’s crows within the late Seventies, and the hassle continues at the moment.
“Our examine confirmed that the rubbish is immediately linked to the crow inhabitants fluctuations,” Nihal Dayawansa, the FOGSL president and a professor of zoology on the College of Colombo, tells Mongabay.
Crows have communal roosts, usually a single tree, or a number of in the identical space, relying on the dimensions of the flock. This makes it simple to hold out a inhabitants evaluation, which the FOGSL researchers do by roost counts at nightfall. Over the many years, they’ve recorded the Colombo crow inhabitants rising from about 50,000 birds in 1980 to a peak of 124,300 in 2006, earlier than dropping under the 100,000 mark, at 98,350, in 2012.
The turning level, Dayawansa stated, was the Colombo Beautification challenge in 2010, which included shutting down a number of open dumpsites that had been thought of eyesores. However after 2014, the federal government largely deserted the challenge, and new dumpsites started showing.
The Colombo crows are predominantly home crows (solely about 5% are large-billed crows), roosting in flocks of as many as 500 people — though figures like this aren’t widespread anymore, Dayawansa says.
Impression on endemic wildlife
The inspiration to start the crow examine got here from a public market close to a faculty the place the birds had change into a nuisance, says Sarath Kotagama, an ornithologist and emeritus professor of ecology from the College of Sri Lanka.
“This market bought shifted to a different space and the crow inhabitants within the space too declined,” Kotagama tells Mongabay.
Through the years, the examine has confirmed that the crows transfer with the rubbish. And it’s not simply open dumpsites that make for simple pickings. In Horton Plains Nationwide Park, one of the vital ecologically delicate areas of Sri Lanka and a UNESCO World Heritage Web site, large-billed crows swoop in with each surge in human guests, due to the massive quantities of trash that the latter generate.
When customer numbers to the nationwide park drop considerably, as was the case all through a lot of the COVID-19 pandemic, the crows lose their essential supply of meals and commenced searching native species. This consists of endemic species just like the Ceylon deaf agama, a lizard discovered solely in Sri Lanka. That raises issues in regards to the influence on native species if the crow inhabitants will increase unchecked, Kotagama says.
Dayawansa says controlling crow populations might be executed by managing the meals sources which might be out there to the birds. This implies an efficient rubbish administration technique, he says. Some nations, resembling Singapore, have crow-culling competitions and different strategies to eradicate the birds.
But when there’s another ethical to the Jataka story from 2,000 years in the past, one which applies to the present-day drawback, it’s that the plate of fish within the nobleman’s kitchen ought to have been absolutely lined to start with.
“Implementing synthetic inhabitants management strategies resembling destroying eggs and culling of adults wouldn’t be crucial,” Dayawansa says, “if rubbish websites are higher managed.”
Citations:
Krzemińska, U., Wilson, R., Music, B. Ok., Seneviratne, S., Akhteruzzaman, S., Gruszczyńska, J., … Rahman, S. (2016). Genetic range of native and launched populations of the invasive home crow (Corvus splendens) in Asia and Africa. Organic Invasions, 18(7), 1867-1881. doi:10.1007/s10530-016-1130-5
Karunarathna, D. M. S. S., & Amarasinghe, A. A. T. (2008). An statement of the jungle crow (Aves: Corvidae) feeding on Ceylon pygmy lizards, Cophotis ceylanica (Reptilia: Agamidae) at Horton Plains. Sauria, 30(4), 59-62. Retrieved from https://www.researchgate.web/publication/259500784_An_Observation_of_the_Jungle_Crow_Aves_Corvidae_feeding_on_Ceylon_Pygmy_Lizards_Cophotis_ceylanica_Reptilia_Agamidae_at_Horton_Plains_NP_in_Sri_Lanka
Banner picture of two large-billed crows photographed contained in the ecologically delicate Horton Plains Nationwide Park in central Sri Lanka, courtesy of Uditha Wijesena.
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