Deformities in birds expose ‘worrisome’ impact of environmental degradation
In 2018, Mohan Bikram Shrestha spotted a white crow near his home on the outskirts of Nepal’s capital Kathmandu, piquing the interest of the conservationist.
He immediately shared a picture of the crow to a Facebook group for local avian enthusiasts, only to receive several similar images reporting abnormalities in birds. Some of the birds appeared to be leucistic, a condition leading to partial loss of pigmentation in their feathers, while others had albinism or overgrown and deformed beaks, also known as avian keratin disorder.
“At first we just coordinated with bird photographers and enthusiasts and maintained a data set,” said Shrestha, senior research officer at Bird Conservation Nepal. “We then thought it was important to study this phenomenon, since there has been no such study in Nepal.”
Last month, Shrestha, along with his colleague Nikeet Pradhan, published the first-of-its-kind report in Nepal documenting avian deformities in the country. Published in the journal Ornis Hungarica, the study documented two dozen cases of deformities in 16 bird species across the country’s 12 districts.
“All the records were found in urban areas with anthropogenic disturbances, suggesting that the major cause could be environmental degradation by humans,” Shrestha and Pradhan wrote in the paper.
Nepal is home to some 878 species of birds, of which 37 are classified as globally threatened species, while 167 have been designated nationally threatened, according to a 2016 report by international conservation charity ZSL on the status of the country’s birds.
In recent years, researchers noted that habitat loss, hunting, infrastructure projects and climate change had proved detrimental to Nepal’s resident and migratory birds.
However, the increasing number of defects in birds has now raised concerns among ornithologists. Shrestha’s study linked most cases of avian deformities to areas near human settlements, suggesting that “anthropogenic toxicants and environmental degradation” could be culprits for such a phenomenon.
“Birds are feeding on food made for humans, including junk and adulterated food items,” Shrestha said.
“Those chemicals might not be suitable for birds and could alter their genes.”
The study found house crows, house sparrows, common mynahs and barn swallows suffering from leucism, avian keratin disorder and unidentified colour aberrations, while migratory birds like the Eurasian coot, Eurasian cuckoo and steppe eagle were also found with similar deformities.
According to the British Trust for Ornithology, beak deformities have been found in more than 60 bird species globally, while one American study in 2010 suggested that the highest rates for such abnormalities in wild bird populations could be found in the states of Alaska and Washington, as well as British Columbia in Canada. Scientists attributed the deformities to several factors, including environmental contamination.
Other studies have also shown that the increase in polluting anthropogenic activities affects the health and survival of birds.
Apart from birds feeding on chemical-laden, unhealthy food items made for human consumption, Shrestha said pesticides used in farms could also be affecting wild and domesticated birds. While pesticide residues in grains could take a longer time to cause diseases in humans, he said a small amount might cause harm in birds much quicker.
Hem Sagar Baral, a conservation biologist and ornithologist, said experts had been witnessing avian deformities for a while, though their frequency might have increased in recent years as more people were photographing and documenting birds. But, he said that over the years, leucistic characteristics in birds had turned out to be a “worrisome trend”.