There is a popular café near Mandya, on the highway from Bengaluru to Mysuru. Here another road splits off and leads to the wetlands of Maddur, 20 km down.
The wetlands are a part of Kokkare Bellur village. “Kokkare” is Kannada for ‘stork’. The village is home to a community reserve for birds and hosts the breeding grounds of the spot-billed pelican and the painted stork. Its residents have adopted the birds as their daughters in spirit.
Unfortunately, 94 spot-billed pelicans have died in Kokkare Bellur since 2016. These birds are classified as ‘near threatened‘. In a recent study, scientists from the Bharathiar University and the Salim Ali Centre for Ornithology and Natural History (SACON), both in Coimbatore, have indicated that the pelicans could have died of an infection caused by roundworms and flukeworms.
The researchers studied the Kokkare Bellur area for six months until May 2018 and found the corpses of about 55 adult pelicans in different stages of decomposition. Only four of them could be used for post-mortem studies. And in these studies, they found worms of the Contracaecum and the Echinostoma species.
Contracaecum is a member of the family of helminth parasites. Worms of this species were found inside the four birds’ gizzards. Many members of this family of parasites are known to infect humans, including Contracaecum itself, with cases having been reported from Australia. The researchers found worms of the Echinostoma species in the birds’ intestines. Although they were fewer in number, they are also more infectious.
Pelicans are piscivores: fish is their major source of nutrients. So when the researchers checked the nine water tanks in the area, they weren’t surprised to find a high load of these parasites in seven of them. They also discovered live worms and their eggs in the guts of fish in the tank.
Speculation had been rife earlier that the birds were dying because of anthropogenic water pollution, including lead contamination. The new results don’t rule them out but also point their fingers at another plausible cause: drought.
Shanthala Kumar, a zoologist at Bharathiar University and one of the study’s authors, said they don’t know where the endoparasites come from but that most wild animals and birds harbour them in large numbers. During a drought, she explained, animals don’t have access to enough food, therefore don’t have enough nutrients, which in turn weakens their immune systems. The endoparasites seize this chance and multiply.
However, the group isn’t clear why the number of pelican deaths spiked in the last two years. P. Sundararaj, Kumar’s colleague at Bharathiar University and another member of the team, speculated that a long drought could have forced the birds to spend more time on the water looking for fish to eat, leaving more of their poop in the water and infecting it. “The result of this entire process is the mortality of pelicans. It becomes a complicated web of infections,” he said.
Kumar added that at a meeting with “forest officials and community members in January”, the team had “the local people and livestock” be screened for infections. “It is [not yet known] if the endoparasites are an outcome of human activity”; forest officials are investigating further.
Either way, that the worms exist come from the water prompted Kumar and her teammates to recommend that officials assess the tanks’ parasitic load and disinfect them before the pelicans are treated.
Kannan Vaithianathan, a wildlife biologist at Sathyamangalam Tiger Reserve, Erode, co-conducted a distribution survey of spot-billed pelicans in India between 2000 and 2004. According to him, “No other region in the Indian subcontinent has witnessed as many pelican deaths as Kokkare Bellur.”
The new study’s results offer him hope. “I was concerned about the situation and was coordinating with the Wildlife Institute of India, Dehradun, to study the cause. This study has provided a new direction, as the lake water has never been screened for nematodes.”
However, he cautioned against getting carried away: even if the study offered a new line of enquiry, it’s still only based on the bodies of four birds. “It might require further research to ensure that these nematodes are the sole cause of mortality.”
Varadarajan Gokula, an ornithologist at the National College, Trichy, asked another pertinent question: “All dead birds that were found are adults. So are the juveniles and subadults free from infection?” He suggested forest officials and researchers also follow-up on live pelicans.
All of these researchers hope that the they’re able to make full sense of the problem soon and resolve it, reinstating Kokkare Bellur’s reputation as a haven for spot-billed pelicans. But in the meantime, according to Kumar, Sundararaj and others, 80% of the birds have abandoned the village and have since been spotted in parts of Bengaluru.
Navodita is the associate editor at i-wonder, a science magazine targeted at middle school teachers published by Azim Premji University.