Now afoot in Western Ghats, a great hornbill mystery

Hubballi: Researchers and citizen scientists studying the hornbill, a large bird with a striking curved bill, are observing something strange this year: females of the species, especially the great Indian hornbill, are abandoning their nesting sites.

This phenomenon, which scientists termed “worrying", has been noticed in five states of the Western Ghats, including Karnataka.

The great Indian hornbill usually raises only one chick a year and any impact in its reproduction cycle would adversely impact the ecology in the longer run. The four-month nesting period of the great Indian hornbill starts in December.

There are nine varieties of hornbills in India, of which Western Ghats is home to four: Malabar pied hornbill, Malabar grey hornbill, great hornbill, and Indian grey hornbill.

Hornbills, which pair for life and raise their chicks in the same nest, are considered as the farmers of the forest, as they are known to disburse nearly 2,000 to 3,000 seeds per day within 250 mts to 10 km of the mother tree.

Researchers are clueless on the reasons for the uncharacteristic hornbill behaviour. But there are some theories on why the birds, a critically endangered species, are abandoning the procreation process, and they range from a lack of availability of fruit resources to high temperature as well as impact of climate at the micro-level. 

Gopalkrishna Hegde of Uttara Kannada district’s Yellapur is a citizen scientist who has been monitoring great Indian hornbill nests for the last nine years. Hegde told DH that a female hornbill visited the nesting site late in the season, entered the tree cavity and left it early without laying eggs.

Even officials in the Kali Tiger Reserve, who were monitoring 13 sites, have a similar tale of hornbills deserting their regular nesting trees.

Pooja Pawar, a research affiliate with the Nature Conservation Foundation (NCF), Mysuru, said that unlike previous years, female hornbills arrived at the nesting sites late this season and abandoned them early.

“As of now, we don’t know the exact reason for this behaviour of the hornbills. But for the first time, we are watching them not using their nest in such large numbers. This phenomenon is being witnessed in Kerala, Karnataka, Maharashtra, Tamil Nadu and Goa,” she said.

She said at a few nesting sites, pied hornbills and grey hornbills have laid eggs and the male feeding the female inside the cavity is being reported.

Shridhar D Bhat, Assistant Professor at the College of Forestry, Sirsi, said the birds, highly sensitive to changes around them, are known for “postponing” the reproduction process if the environmental conditions are not conducive.

“It would be too early to say the exact reason for birds not nesting this season. One of the reasons could be that due to drought and low production of certain fruits, the male might have found it difficult to fetch the required variety and quantity of fruits for the female,” he said.

During the gestation period, the female hornbill sheds all her feathers inside the nest and covers the mouth of the cavity with mud to neutralise any threats. The female and the chick are completely dependent on the male to provide them with food.

NCF Scientist Rohit Naniwadekar expressed concern. "There is a need for long-term monitoring of hornbill nesting and climate across the length of Western Ghats to definitively ascertain the reasons," he said.

According to him, "possible factors include changing climate patterns with cascading influences on fruit availability and hornbill nesting, among others."

Highlights - Bizarre behaviour The reasons for female hornbills abandoning nesting sites range from a lack of availability of fruit resources to high temperature and impact of climate at micro-level  In Uttara Kannada district’s Yellapur, a female hornbill visited the nesting site late in the season, entered the tree cavity and left it early without laying eggs Officials in the Kali Tiger Reserve, who were monitoring 13 sites, have a similar tale of hornbills deserting their regular nesting trees Any impact on hornbill reproductive cycle would adversely impact the ecology in the longer run

Quote - As of now we don’t know the exact reason for this behaviour of the hornbills. But for the first time we are watching them not using their nest in such large numbers. This phenomenon is being witnessed in Kerala Karnataka Maharashtra Tamil Nadu and Goa - Pooja Pawar research affiliate Nature Conservation Foundation Mysuru