By Sadiqur Rahman
Every dusk in the University of Dhaka campus, in Bangladesh’s busy capital city of Dhaka, the canopies of the taller trees like Gogon sirish (Albizia richardiana), or Raj koroi, trees shake as flocks of black kites (Milvus migrans) descend onto the branches.
Before their final landing for the day in their roosts, the communal raptors soar high in circles over the canopies, declaring their roosting territories together.
However, the sight of soaring black kites over some Gogon sirish trees has become a rare sight across the vast 306-square-kilometer (118-square-mile) expanse of Dhaka city, which has become urbanized in an unplanned manner at the cost of wetlands and numerous mature trees. This transformation also indicates the degrading habitats of all urban raptors.
In April and May this year, the Bangladesh Forest Department’s wildlife inspectors rescued at least 35 black kites, exhausted and collapsing midair during their flights, from several localities in Dhaka.
According to rescuers, it is mostly the juvenile black kites that become sick while searching for suitable perches between their common foraging and roosting sites.
“Commonly, a young bird that has just completed its fledgling stage hones its flying skills by completing short trips from one tree branch to nearby ones. When it struggles to find trees amidst a jungle of concrete and eventually loses the minimum energy to fly, it may collapse,” Ashim Mallick, a wildlife inspector, told Mongabay.
Before their final landing in their roosts, the communal raptors soar high in circles over the canopies, declaring their roosting territories together. Image by Sadiqur Rahman.
Disappearing roosts
To understand the roosting habits of black kites in Dhaka city, researchers conducted a survey around the University of Dhaka campus, Ramna Park, Suhrawardy Udyan (park) and Osmani Udyan (park), the prominent green areas in the city.
The survey recorded 38 roosting sites, the highest being at the University of Dhaka, which had 19 of them. Moreover, the researchers found that 92 percent of roosting sites were trees belonging mostly to the Fabaceae family, and 8 percent were man-made structures like telecommunication towers and high-rise buildings.
Regardless of the roosting sites, the study’s results suggested that black kites avoid sound pollution and human crowds.
Among the localities where rescuers found the sick birds include Azimpur, Mirpur, Kazipara, Uttara, Tikatuli, Banani, Motijheel, and Shyamoli. These areas are overpopulated, noisy and unsuitable for black kites’ roosting.
Professor Mohammad Firoj Jaman, a faculty member of University of Dhaka’s zoology department, says black kites’ feeding habits and habitat loss are related.
Dhaka city generates 2.7 to 2.9 million tonnes of waste every year, about 70 percent of which is food-related organic waste. Since the city produces a huge amount of waste, there should not be a food scarcity for the black kites.
However, unlike previous decades when waste dumping was haphazard, it now takes place at a few designated secondary transfer stations and landfills.
“As observed, these dumping sites and surrounding areas feature no big trees. That’s why black kites must fly long foraging trips between their roosting times, which requires more energy,” Jaman explained.
A 2021 study pointed out that Dhaka city lost 56 percent of its vegetation as its urban cover increased by 82 percent between 1989 and 2020.
Wildlife inspection Ashim Mollick holding a rescued Black kite on his arm. Image by Sadiqur Rahman.
Unfavorable weather
Another concern that’s been on the rise is extreme weather events like heavy rainfall and heatwaves, which may exhaust the birds that already facing habitat loss and food scarcity.
Rain is generally suggested to impair or prevent foraging, and the effect of rising temperature is usually considered positive. Studies suggest that unfavorable weather often impairs the foraging performance of parent black kite individuals, thus decreasing their food availability and eventually affecting their breeding success.
On May 27, a black kite fell from a tree at a hospital garden in Shyamoli when Dhaka city braced heavy rainfalls following the impacts of Cyclone Remal. Shafiqul Islam, a hospital staff, rescued the bird and tried taking care of it at home.
“It was completely drenched in rain, unable to walk and fly. It refused food and water at my home. As the bird’s condition was deteriorating, I sought help from the forest department,” Shafiqul said. The next day, wildlife inspectors took the sick black kite into their custody, let the bird get completely dried under the sun, and provided it with necessary fluids and food.
Earlier on April 30, forest department staff rescued an a dehydrated black kite from a residential area in Banani. Dhaka temperatures peaked at 40.5°C (104.9°F) the previous day, the second-highest in 59 years.
In neighboring India, the daily newspaper Hindustan Times reported on May 22 that black kites were the worst affected among birds by extreme heat in New Delhi, a city that has a sizeable population of black kites. Wildlife SOS, a conservation organization in India, reports that the kites, which can be found soaring at high altitudes, frequently collapse from heat stroke while making a descent.
Regardless of the roosting sites, Black Kites avoid sound pollution and human crowds. Image by Sadiqur Rahman.
Poisonous food
Besides degrading habitats and extreme weather, the scarcity of food and consumption of poisoned food may also be endangering black kites in Dhaka.
These carnivorous raptors have broad diets and feed on several animal species. They are considered insectivores, piscivores, and scavengers.
Some Bangladeshi researchers analyzed the food intake of the black kites in Dhaka and found that they commonly consume offals of chicken, beef and fish besides carrion, human food leftovers and garbage at landfills. In other regions without garbage, they catch insects, rats, fish, chicks of other birds and earthworms.
Allama Shibli Sadik, an ornithologist at the forest department’s wildlife rehabilitation facility Sheikh Kamal Wildlife Center, suspects black kites may fall sick after consuming poisoned food. “Often, insects and rats are killed by pesticides. Chicks often die of viral fever, and all the dead animals end up at the dumping sites,” Sadik told Mongabay, adding that more research is required to understand the consequences of consuming poisoned food.
Concerns over decreasing population
Despite a lack of intensive research on and regular monitoring of black kites in Dhaka, experts have observed that the population of Black Kites has been decreasing drastically in recent years.
A population survey in 2015-2017 estimated approximately 1,300 black kites in Dhaka. Another survey between October 2017 and January 2018 found around 825 black kite individuals in the same city.
Jaman, the zoology professor, says, “I presume that the present population of black kites in Dhaka has dropped to almost half of what we observed decades ago. Due to habitat loss, the birds might have migrated to other places.”
Citing the IUCN Red List of Bangladesh (2015), although he admitted that the black kite is a ‘Least Concern’ species, he warned Dhaka would lose the bird if there is no conservation effort.
Why are black kites important? The role of the species as city scavengers is crucial as they clean up and prevent contagious diseases from spreading.
“An adequate number of avian scavengers like black kites can devour two-thirds of the waste at a dumping site. This means the birds can alleviate the burden of a city’s waste management,” Jaman said.
Considering black kites’ scavenging as one of the important contributions to keeping the city environment clean, Jaman urges concerned people to preserve the existing black kite habitats in Dhaka, especially the taller trees at the University of Dhaka campus and nearby parks.
Banner image: Exhausted black kites may collapse while struggling to find suitable roosts amidst a jungle of concrete. Image by Mohiul Islam.
Citations:
S. Hasan, A.M.M.K. Abedin, A.K.Sarker & H. Naner(2021). Roosting of black kites (Milvus migrans) in Dhaka Metropolis, Bangladesh. Taprobanica, The Journal of Asian Biodiversity, v10i1.252. doi:10.47605/tapro.v10i1.252
Haque, M. A., Ahammed, R., Monirujjaman., Islam, M. A., Khan, M. N. H., Rayan, S. A., Khan, M. M. H., & Kabir, M. M. (2021). Population status and feeding behavior of black kite (Milvus migrans) in Dhaka city, Bangladesh. Jahangirnagar University Journal of Biological Sciences, 9(1-2), 35–48. doi:10.3329/jujbs.v9i1-2.53705
Sergio, F. (2003). From individual behaviour to population pattern: Weather-dependent foraging and breeding performance in black kites. Animal Behaviour 66(6):1109-1117. doi:10.1006/anbe.2003.2303
Nawar, N., Sorker, R., Chowdhury, F. J. and Rahman, M. M. (2022). Present Status and Historical Changes of Urban Green Space in Dhaka City, Bangladesh: A Remote Sensing Driven Approach. Environmental Challenges Volume 6. Elsevier. doi:10.1016/j.envc.2021.100425
Hille, S and Thiollay, Jean-marc. (2001). Bird Conservation International, Volume 10, Issue 4, pp. 361 – 369. Cambridge University Press. doi:10.1017/S0959270900000319
This article was originally published on Mongabay
