Credit: Saikat Banik, Alex Jacob & Harindra Baraiya
Each year, during October and November, the northeast Indian states await the arrival of winged visitors that beckon birdwatchers worldwide. Congregating in the thousands, the Amur falcons — tiny raptors as heavy as your phone — speckle the skies as they migrate from their breeding grounds in southeast Russia and northern China, to the wintering grounds in Southern Africa. The iconic journey of nearly 22,000 kilometres—about half the Earth’s circumference—is the longest sea crossing of any raptor.
But the birds do not accomplish this tremendous trans-oceanic fete in one go. On their way, they stop over in northeast India, earning Nagaland its name— ‘the falcon capital of the world.’ The arrival of Amur falcons has also aroused the curiosity of many scientists, including wildlife biologist Suresh Kumar at the Wildlife Institute of India. He first began studying the bird’s legendary migration using satellites nearly a decade ago.
“We knew nothing about the Amur falcons,” Kumar says, discussing the lack of our understanding of these birds when he started his research. As he dug further into their behaviour, he encountered more questions than answers. Why do the birds arrive in October and November? Why do they stay for nearly two weeks instead of a few days? If they do eat during their stay, what do they feed on? Why do they stop over in landlocked northeastern states instead of the Western Ghats closer to the Arabian Sea?
When Kumar and his colleagues began putting the pieces together, they found that an unassuming insect — the humble termite — was at the centre. “The entire story is driven by termites,” he says, “It is the termites that are calling the shots.”
In a study published in the Journal of Raptor Research, Kumar and his colleagues report that Amur falcons stop in northeast India for about two weeks to feed on termites and gain the energy they need to fly across the ocean to Africa. Most of their diet comprises two species of termites. Interestingly, the birds time their arrival exactly when these insects termites swarm.
A seasonal delicacy
Amur falcons primarily feed on insects and occasionally eat small birds and rodents. Studies from Southern Africa have shown that these birds eat insects from five different families (or orders): Orthoptera (grasshoppers, locusts and crickets), Isoptera (termites), Hemiptera (cicadas, aphids and planthoppers), Coleoptera (beetles) and Hymenoptera (bees, wasps, hornets, sawflies and ants). While there was anecdotal evidence of the birds feeding on flying termites in northeast India, scientific knowledge about their diet was sparse. The study is the first to shed light on this vital knowledge.
The researchers scouted the forest floor for regurgitated pellets to find out what Amur falcons eat. Like all raptors, the Amur falcons eat their prey as a whole instead of tearing them apart. In the morning, they spit out the undigested parts as pellets. The researchers collected nearly 1,500 such pellets between 2017 and 2019 from three stopover sites in Nagaland (Pangti, Yaongyimchen, and Hakhizhe) and one each in Assam and Manipur, where more than 1 lakh birds gather. The researchers then looked at every pellet under a microscope—a tedious task—to identify the species of insects based on their remains.
“You do not find the termites as a whole,” explains Kumar, “You would find pieces and pieces of it.” Thankfully, the termite heads stayed intact, which the researchers counted. They found that almost nine in 10 pellets had remains of termites, most of which belonged to two species: the South Asian wood-destroying termite (Odontotermes feae) and Odontotermes lorni. Both are fungi-farming termites native to the Indian subcontinent.
The study found that about 98% of pellets from birds roosting in Yaongyimchen had termites—the most from a site. By weighing the remains, the researchers estimated that one falcon could eat up to 134.4 grams of termites over 15 days — the typical duration of their stopover. If a million Amur falcons stopped over, they would eat close to two billion termites during that period!
The birds do not have to sweat it for their sumptuous dinner. Just as the birds arrive, the underground termites emerge in their nuptial flights — a period where they acquire wings and mate. That window, however, is short (about 45 minutes) and precisely timed (before sunset). “All that the falcons need to do is wait,” says Kumar, “They do not really need to be expending energy on trying to go and scout for food.” By timing their arrival to coincide with the termites' emergence, the birds fill their energy stocks with nutrition-rich, easy-to-digest food and do so without spending many calories.
“It is amazing to know that the emergence of winged termites and the arrival of Amur Falcons coincide,” says ornithologist Asad Rahmani, who served as the director of the Bombay Natural History Society and was not involved in the study, “This shows how nature is intricately connected.”
While the termite feast powers the Amur falcons’ transcontinental flight, it also plays the role of pest control. “Termites cause damage to rice, wheat, barley and maize by feeding on the roots and stems,” says migratory bird zoologist Suman Pratihar, who was also not a part of this study. Amur falcons, he says, are also called ‘loi’ or ‘insect eaters’ in parts of Northeast India, and “they control termite population [which is] much needed for crop protection.”
Pest control under threat?
Until 2012, the local people in parts of Northeast India hunted Amur falcons in large numbers for their meat. Following years of awareness and ecotourism initiatives, the stopover sites are now a haven for the birds. On the IUCN Red List — a database of species that face extinction risk — the Amur falcon is classified under ‘Least Concern,’ implying these birds have no immediate risk. But Kumar says that is no reason to be complacent as we do not know the number of birds that visit India yearly. “It is very important to monitor what's going on,” he says.
“In the case of Amur falcons, their protection from poaching is not enough - we have to protect their food sources too,” adds Rahmani, “The whole environment needs to be protected if we want to save the Amur falcons.”
The close connection of the falcons’ diet with the emerging termites raises new concerns. Since nearly half of the birds that arrive are young juveniles on their first migratory flight, eating nutritious food is critical to their survival. “If there is not enough food, a certain proportion of these birds die in the Arabian Sea—they are not going to make it across,” Kumar warns.
Slash-and-burn agriculture, widely practised in northeast India, may affect the termites, although further studies are needed to confirm this. As termites’ emergence is closely linked to the monsoon, whose patterns studies show are changing with the warming climate, scientists are not sure how that may impact the falcons’ arrival and diet. “It is so complex a question to address.”
Regurgitated pellets from the falcons were examined under the microscope to determine which species were included in prey remains.
Credit: Saikat Banik, Alex Jacob & Harindra Baraiya