Udupi, Oct 1: The Malabar Pied Hornbill, a striking forest-dwelling bird more commonly seen in the dense canopies of the Western Ghats, is now making unexpected appearances in urban areas of Udupi, sparking excitement among birdwatchers and wildlife enthusiasts alike.

Spotted in places such as Brahmagiri and Ambalpady, these hornbills have been seen perched on tall city trees—an unusual sight that has turned the heads of both residents and naturalists.

While the species is not new to the Udupi district, ornithologists say its increasing presence within city limits is both surprising and noteworthy.

“Malabar Pied Hornbills are typically seen deep inside forested landscapes. Their arrival in urban zones is unexpected and definitely worth paying attention to,” said local birdwatchers observing the trend.

Forest giants move to the city

Known for their bold black-and-white plumage and curved, yellow-black beaks, the Malabar Pied Hornbill is usually found in evergreen and moist deciduous forests, particularly along riverbanks. Their diet includes fruits, small animals, insects, and even reptiles, but they are especially fond of figs, which may be drawing them into fruiting city trees during specific months.

The species is also famous for its unusual nesting habits. During breeding season, the female hornbill seals herself inside a tree cavity using a mixture of her own droppings and mud, leaving only a narrow slit open. Through this, the male delivers food until the chicks are ready to leave the nest.

Experts warn, however, that rapid habitat loss and deforestation have led to a decline in hornbill populations across the Western Ghats.

‘They may be nesting here now’

“There is a strong possibility that these hornbills have now found a permanent nesting habitat in Udupi, particularly in tree hollows on large trees located on the city’s outskirts,” said Tejaswi S. Acharya, trustee of the Manipal Birding and Conservation Trust.

“We’ve even seen them roosting on the Makada tree near Udupi city bus stand. Our birdwatching team has encountered them several times in recent months,” he added.

Not just passing visitors

Bird expert V Lakshminarayana Upadhyaya noted that hornbills were once only seen after long trips to places like Dandeli, deep in the Western Ghats. But that has started to change.

“For the past three to four years, we’ve been spotting groups of Malabar pied hornbills in urban areas like Kundapura and Udupi. They’re not present throughout the year, but are especially visible during August and September, likely drawn by fruiting trees,” he said.

He also pointed out that increased human interference in their native forest habitats could be pushing the birds toward the coastal belt, where tall trees and seasonal food sources are still available.

Urban sightings: A conservation alarm or adaptation?

The hornbills’ shift into Udupi city areas is being seen as both a welcome development for local wildlife lovers and a warning sign of habitat displacement. Their presence in urban zones may indicate adaptive behaviour—or more worryingly, a retreat from threatened forest ecosystems.

With sightings now reported over consecutive years, bird experts believe this could mark a long-term behavioural shift, and stress the need for urban tree conservation to support species adapting to changing environments.

The presence of a Malabar pied hornbill roosting in Udupi city signals significant habitat disruption, with experts noting the species’ adaptation to new environments as pristine forests dwindle. The hornbills’ move from their usual riparian forest habitats to urban areas indicates they are searching for food and roosting trees in modified landscapes. 

An important seed disperser in deciduous forests, the Malabar pied hornbill has had to adapt and contend with the reality of dwindling natural habitats

I was in Pench Tiger Reserve, Madhya Pradesh, watching a pair of jackals feeding on a carcass when a loud beating of wings broke through the treetops. I looked up to find a male Malabar pied hornbill (Anthracoceros coronatus) settled on a fig tree. My heart leapt; it was my first sighting of this magnificent bird. Years later, I remember the wonderful sight vividly. This prehistoric-looking bird, perched on a tree, was regurgitating fruits and leaning forward to push it into a gash in the trunk. Presumably, it was feeding these fruits to its mate, who was sequestered in a cavity nest. During nesting, female hornbills wall themselves into holes in trees to lay their eggs and raise the chicks once they hatch, while the male keeps his mate and offspring fed and healthy. There is something so tender and heartwarming about how these hornbills care for one another.

India has nine species of hornbills, of which the Malabar pied hornbill is spread across parts of Central and Eastern India, in Madhya Pradesh, Andhra Pradesh, Odisha, and Bihar, and in the Western Ghats, in Maharashtra, Karnataka, Tamil Nadu, Goa, and Kerala.

They look similar to their northern cousin, the Oriental pied hornbill (Anthracoceros albirostris), but can be differentiated by a larger body and greater head and casque size. Malabar pied hornbills feed mainly on fruits; figs are a favourite. These hornbills are often found by the margins of rainforests, venturing to plantations and other similar areas with fruiting trees in search of food. They also eat termites, fish, crabs, small reptiles, and even young birds and other small animals. With pristine forest habitats dwindling, most species face the dilemma of adapting to newer, more disturbed habitats — or facing extinction. Malabar pied hornbills appear to be among the more adaptable species.

I was in Pench Tiger Reserve, Madhya Pradesh, watching a pair of jackals feeding on a carcass when a loud beating of wings broke through the treetops. I looked up to find a male Malabar pied hornbill (Anthracoceros coronatus) settled on a fig tree. My heart leapt; it was my first sighting of this magnificent bird. Years later, I remember the wonderful sight vividly. This prehistoric-looking bird, perched on a tree, was regurgitating fruits and leaning forward to push it into a gash in the trunk. Presumably, it was feeding these fruits to its mate, who was sequestered in a cavity nest. During nesting, female hornbills wall themselves into holes in trees to lay their eggs and raise the chicks once they hatch, while the male keeps his mate and offspring fed and healthy. There is something so tender and heartwarming about how these hornbills care for one another.

India has nine species of hornbills, of which the Malabar pied hornbill is spread across parts of Central and Eastern India, in Madhya Pradesh, Andhra Pradesh, Odisha, and Bihar, and in the Western Ghats, in Maharashtra, Karnataka, Tamil Nadu, Goa, and Kerala.

They look similar to their northern cousin, the Oriental pied hornbill (Anthracoceros albirostris), but can be differentiated by a larger body and greater head and casque size. Malabar pied hornbills feed mainly on fruits; figs are a favourite. These hornbills are often found by the margins of rainforests, venturing to plantations and other similar areas with fruiting trees in search of food. They also eat termites, fish, crabs, small reptiles, and even young birds and other small animals. With pristine forest habitats dwindling, most species face the dilemma of adapting to newer, more disturbed habitats — or facing extinction. Malabar pied hornbills appear to be among the more adaptable species.

The presence of forest-dwelling Malabar pied hornbills roosting in Udupi city is considered a significant warning sign by experts. Their move into an urban environment is likely a signal of habitat degradation in their native Western Ghats forests, forcing the birds to adapt to human-modified landscapes to find resources. 

The setting sun cast an idyllic glow over the Kadra backwaters of the river Kali. “They will come,” said CR Naik, “I know”. His companions were my friends Sachin and Bhuvan who were visiting the Kali Tiger Reserve, in north Karnataka. They vividly recounted to me how they were unconvinced at first — after all one doesn’t see Malabar pied hornbills on a wish. Then it began. First there was one bird, followed by ten. The hornbill numbers swelled, filling the evening air with their raucous cacophony, feeding in a grove of poison nut (Strychnos nux-vomica) trees and then flying across to roost on a little island in the river. Sachin, Bhuvan and Naik counted 120 Malabar pied hornbills.

CR Naik works as a forester in the Karnataka Forest Department. He is passionate about all wildlife, and hornbills hold a special place in his heart. Naik has monitored nests of Malabar pied hornbills for many years and takes immense pride in “guarding” them until the chicks fledge. He understands their needs and habits and likes to introduce people to the lives of these birds.

Hornbills are fascinating and funky birds. There are 54 hornbill species found on Earth today. With their large beaks and characteristic headgear — a boxy chamber called a casque — each could be a winning entry in a costume party. The Malabar pied hornbill (Anthracoceros coronatus) is endemic to the Indian subcontinent and found as three disjunct populations in the Western Ghats, Central Indian forests, and Sri Lanka. There have also been some recent reports of it breeding in the Satpuras.

The Malabar pied hornbill has dapper black-and-white plumage: jet-black neck and neat white underparts make it seem like they are dressed for a tuxedo party. Their black wings have white tips that form a halo when in flight. White margins flank the long black tail. Malabar pied hornbills can be 65-90 cm long and weigh about a kilogram. They call in loud raucous cackles (that sound like kleng-keng or kak-kak) interspersed with squeals.

Most hornbills show what biologists call sexual dimorphism — the male and the female differ in size and looks. Dimorphism in the Malabar pied hornbill is not stark, but females tend to be slightly smaller than males. Their faces and casques differ a bit. Females have their eyes fringed by bare skin that looks white to pale bluish; the male lacks this pale skin patch. Both sexes have a white patch on the side of the neck. The large cream-yellow beak carries atop it an over-sized casque that earns this group of birds their moniker “hornbills”.

In the Malabar pied hornbill, the casque ends in a single point (compared with the great hornbill that has a squarish end). As with other large hornbills, the casque of the Malabar pied hornbill looks like an awkwardly placed clunky crown. I love watching these birds swivel their casqued heads when trying to get a good look at you, one eye at a time, beyond the big beak. The casque might look heavy, but it is hollow and made of keratin (same as human fingernails). It supposedly acts as a resonating chamber to amplify sounds when the birds call.

Malabar pied hornbills prefer moist but slightly open forests. They usually move around in small groups of up to 10 birds. Sometimes though, many tens of them gather at large fruiting trees or roosts, like the little island in the Kali backwaters. In some places like Dandeli Wildlife Sanctuary, flocks of 100 or more are regularly seen in areas with plenty of fruit trees. Although Malabar pied hornbills will usually stay up in the canopy, they occasionally come down to the ground for a dust-bath. It is surmised that this beauty regimen helps disinfect the spaces between the feathers and keeps parasites at bay.

Hornbills have fascinating breeding habitats. Like many other hornbills, the Malabar pied hornbill makes its nest in the natural cavities of old trees, about 4-15 m above ground, and favours large trees such as Tetrameles nudiflora and Terminalia bellerica. Both parents tend to the young. Sometime in March-April, the female seals herself into the nest cavity. She blocks the entrance with poop, mulch and pulp and for almost a month incubates a clutch of two to four eggs. The male, during this time, ferries food to its house arrested mate. The female comes out of the nest cavity when the oldest chick is about 3-4 weeks old and then helps the male feed the chicks. The chicks stay inside the cavity for a few more weeks until they become ready to fledge.

The fruit-dominated diet of the Malabar pied hornbill probably means that it plays a role in dispersing (or spreading) the seeds of many tree species. Studies from Northeast India and Southeast Asia indicate that hornbills farm the forest, maintaining the diversity of tree species that they feed upon. We may expect the Malabar pied hornbill to play a similar role where it is found, but we do not know as yet.

As with so many other creatures on Earth today, the Malabar pied hornbill has to contend with humans to survive. Some of its troubles are common to large-bodied animals everywhere. Space, for instance. These birds largely eat fruits, which tends to be a patchy resource in a forest. Trees bear fruit only during select parts of the year, which differs among species, and not all trees of a species will fruit. So, a group of Malabar pied hornbills need a large patch of forest that contains enough fruit trees to sustain them through the year. The breeding habits of the Malabar pied hornbill also has it depend on old trees, preferably large ones, with natural cavities. Old trees exist mostly in old-growth forests, being rare even there.

Agriculture, plantations, roads, mines, and other human land-use have not only reduced the forest available to these birds, but also fragmented remaining forests into smaller parcels that may be insufficient to support the needs of hornbills. Forest fragments often have large old trees dying out, making nest trees scarce. Fruit tree species favoured by hornbills can decline in disturbed, fragmented forests, creating a shortage of food resources. Logging operations can render even large forest patches unsuitable for hornbills. Hunting remains a threat to these birds. The Malabar pied hornbill has been ranked “near threatened” by the IUCN and experts think that Malabar pied hornbill numbers may be declining.

Hornbills, including the Malabar pied hornbill, are among the most charismatic and splendid birds, but much remains to be known about their ecology. Perhaps because these big birds can be elusive and relatively rare, they are hard to study. There are few programmes in India dedicated to a long-term understanding of hornbill ecology, but hopefully this will change soon with many young wildlife biologists devoting themselves to the study of these amazing birds. Meanwhile, unsung heroes like CR Naik will keep guard over hornbills and their habitats.

Key takeaways from the Udupi observation

• A “conservation alarm”: While an interesting sight for residents, experts view the hornbills’ presence as an indicator of habitat displacement and fragmentation in their natural environment.
• Adaptive behavior: The hornbills are demonstrating adaptability by utilizing large trees in urban areas for roosting and possibly nesting, and finding fruiting trees like figs for food.
• Long-term shift: Bird experts believe that repeated sightings over several years indicate this might be a long-term behavioral shift, not just a passing visit.
• Not a new phenomenon: Similar behavioral changes have been noted in other hornbill species. A study in Indore, for example, observed Indian grey hornbills nesting in a concrete cavity and consuming human food like bread and biscuits. 

Adaptation is one of the key requirements for successfully evolving and staying alive in the race of “the survival of the fittest”. The Indian Grey Hornbills of Indore are playing by these rules and have adapted to a highly urbanized environment created by human beings. In the concrete jungles where there are very few trees left, these members of the bird family known for their elaborate arrangements of creating nests in tree holes and plastering it with mud, have learnt to build nests in crevices in multi-storied buildings and feed on food such as rotis and biscuits.

“This is the first recorded evidence of change in nesting and breeding behaviour of Hornbills, when a pair of birds has been spotted nesting inside a cavity in a building,” said ornithologist Ajay Gadikar who made the discovery and documented the adaptive behaviour of grey hornbills.

“It is exciting that Hornbill is evolving and adapting to its surroundings, which increases its chances of survival. But at the same time it indicates that there are not enough trees in the city to host birds,” said Gadikar speaking about the resourcefulness of the pair of birds.

From Trees Cavities to Building Crevices

Nesting season of Grey Hornbills lasts for about 3 months from March to June. During this time the mating pair looks for a tree hole with ample space for the eggs to hatch and the hatchlings to comfortably live until they are old enough to come out of the hole. The mom shares this home by sealing the nest entrance using its excreta and mud-pellets supplied by the male.This is to allow the female to put her beak out and get the food supply from the male in her self-made maternity home while she waits for her eggs to hatch and later the chicks to grow older safely tucked inside from prying and hungry predators.

Gadikar has been studying the behaviour of grey hornbills for two years and observed previously the change in food habits of these birds. He found, the hornbills had already started altering their choice of food owing to lesser wild berries and fruits and more man-made food available in their rapidly changing surroundings.

“Hornbills, who usually feed many insects to the chicks, were found to feed rotis (Indian bread) and biscuits in the daily diet of the chicks as well. It seems this bird species are now trying to adjust to the new environment and prepare their chicks for a situation wherein they may have to survive amidst fewer trees and some supplementary diets,” he said.

Explaining on the new and unique nest of the Hornbills, Gadikar said the nest was created inside a cavity left in a wall, along a window around 3 inches in diameter and 20 feet above the ground, The female hornbill had almost totally sealed the window leaving only a small slit-like opening.

Grey Hornbill and it’s Concrete Nest, Courtesy Times of India

“I observed the nest regularly for around 10 days and found that the nest was occupied one-and-half month’s back and presently the chicks are fledged in. I was able to hear calls made by the chicks demanding food, as and when the male hornbill comes to feed the female and chicks,” he said.

Further, the hornbills are learning to live unobtrusively in an area which is heavily populated. The building which is located near a big playground has a lot of activity through the day. The male hornbill takes care to bring food for the female and chicks without drawing attention to itself.

A bird used to living in natural tree cavities for generations and generations has now evolved to live in concrete homes devoid of the smells and signs of Mother Nature’s handiwork but still giving it a chance to secure its future.

Habitat changes impacting hornbills

Hornbills are large, wide-ranging birds that are highly dependent on forest ecosystems. Habitat loss and fragmentation pose a serious threat to their survival. 

impact of deforestation on Hornbill habitat.

According to the Global Forest Watch 2020 report, Arunachal Pradesh lost 1,110 sq.km. of primary forest from 2002-2019. High rate of deforestation in a major hornbill habitat in Arunachal Pradesh causing loss of hornbill species. Papum Reserve Forest (RF) adjoining the Pakke Tiger Reserve as well as a part of Assam affected by illegal felling and ethnic conflict which is a nesting habitat of three species of the large, colourful fruit-eating hornbills: Great, Wreathed and Oriental Pied.

Hornbills

Hornbills are unique birds. They get their name from the horn-like projection called a casque on top of their beak. They are larger than other forest birds. Hornbills are flashy with their over-sized beaks, bright skin around their eyes and long eyelashes. Most have a brilliantly coloured pouch of loose skin at their throat in which they carry fruits, their favourite food.

Hornbills indicate the prosperity and balance of the forest they build nests in. As play active role in dispersing the seeds of many tropical trees and keep the forest alive, called as ‘forest engineers’ or ‘farmers of forest’.

Diversity and Distribution of Hornbills

Hornbills are large and wide-ranging birds and most species are dependent on tropical forest habitats that contain large and tall trees. As they mostly eat fruits, a diversity of native forest tree and liana species are needed to provide their year-round requirements. India is home to nine species of hornbills, of which two are endemic. India is positioned between two bio-geographic realms, the Afro-tropical and Indo-malayan.

India has nine hornbill species, of which four are found in the Western Ghats: Indian Grey Hornbill (endemic to India), the Malabar Grey Hornbill (endemic to the Western Ghats), Malabar Pied Hornbill (endemic to India and Sri Lanka) and the widely distributed but endangered Great Hornbill. India also has one species that has one of the smallest ranges of any hornbill, the Narcondam Hornbill, found only on the island of Narcondam.

Hornbills Threatened in India

The Rufous-necked Hornbill is listed as ‘Vulnerable’ by the IUCN, while the Great Hornbill, Brown Hornbill and the Malabar Pied Hornbill are listed under the Lower risk/Near threatened category. Other Hornbill species in India are listed as ‘Least Concern’. Ten globally threatened Hornbill species, of which two species occur in India, the Rufous-Necked Hornbill and the Narcondam Hornbill, while three species Malabar Grey Hornbill, Malabar Pied Hornbill and the Brown Hornbill are listed as ‘Near threatened’.

Six species of hornbills are listed in Schedule I of the Wildlife Protection Act of India (1972), the Great Hornbill, Rufous-necked Hornbill, Wreathed Hornbill, Narcondam Hornbill, Oriental Pied Hornbill and the Brown Hornbill. Surprisingly, the endemic Malabar Grey Hornbill and the generally rare Malabar Pied Hornbill are not listed in any Schedule.

Hornbills used to be hunted for their casques — upper beak — and feathers for adorning headgear despite being cultural symbols of some ethnic communities in the northeast, specifically the Nyishi of Arunachal Pradesh. But a 20-year-old conservation programme entailing the use of fibre-glass beaks defused the threat to the birds to a large extent.

Illegal logging, however, has led to fewer tall trees where the birds nest. While the protected areas such as Pakke are better guarded, the forests are often under pressure due to agricultural expansion, conversion to plantations or logging.

Conservation Initiatives

In the Western Ghats, a conservation program is underway for the last decade in the Vazhachal forests in Kerala to monitor and protect Great Hornbill and Malabar Pied Hornbill nests with the Kadars, a local tribal community.

In north-east India, the Hornbill Nest Adoption Program to protect Hornbill nests and habitat in reserve forest areas outside the Pakke Tiger Reserve, Arunachal Pradesh has been initiated from 2011.

In Arunachal Pradesh, a program to distribute artificial Great Hornbill beaks (fiberglass substitutes) in 2004. This has created awareness among many community members in some areas in Arunachal Pradesh. The program was an initiative of the Wildlife Trust of India and the Arunachal Pradesh Forest Department.

Conclusion

Several zoos are involved in supporting Hornbill research and conservation in the wild in different ways apart from education activities. Apart from this, a better documented conservation initiatives give visible results, also efforts should be perform to include locals in the conservation programme to protect the hornbills. Simultaneously put ban on hunting of hornbills along with other wildlife and the imposition of fines by local village councils and community members.

• Reliance on large trees: Hornbills require large, mature trees for nesting in natural cavities. Logging, agricultural expansion, and other development activities are causing a scarcity of these crucial nesting sites, even within forest fragments.
• Search for food: As fruiting trees become scarce in their native forests, hornbills are forced to search for food in new areas. This draws them into human-dominated landscapes where suitable fruiting trees, such as fig trees, are still available.
• Reduced forest quality: Inadequate food resources and hunting pressures in degraded forest habitats force hornbill populations to disperse in search of suitable foraging and nesting areas, including moving closer to human settlements. 

1. Introduction
   Asian forest hornbills are an iconic group of large birds with unique breeding biology and a predominantly frugivorous diet
   (Poonswad et al., 2013; Kinnaird and O’Brien, 2007). They play an ecologically important functional role as seed dispersers (Kitamura,
   2011).

• Corresponding author.
  E-mail address: aparajita@ncf-india.org (A. Datta). 1 Authors have contributed equally
  Contents lists available at ScienceDirect
  Global Ecology and Conservation
  journal homepage: www.elsevier.com/locate/gecco
  https://doi.org/10.1016/j.gecco.2024.e02868
  Received 14 October 2023; Received in revised form 18 January 2024; Accepted 27 February 2024

Most hornbill species are threatened due to hunting pressures and habitat loss (Kinnaird and O’Brien, 2007; Poonswad et al., 2013).Of the nine species in India, six hornbill species occur in the Eastern Himalaya region, of which three are classified as Vulnerable in the IUCN Red List – these are the Wreathed Hornbill Rhyticeros undulatus (BirdLife International, 2018), Great Hornbill Buceros bicornis and
Rufous-necked Hornbill Aceros nipalensis (2020a, 2020b). Given the threats of deforestation and hunting across their global range, these hornbill species are projected to decline by 30–49% over three generations (BirdLife, 2018; BirdLife International, 2020a, 2020b). All three threatened species require large tracts of relatively undisturbed forests, however forests are being lost to illegal logging, land conversion for settlements, agricultural expansion, and commercial cash crop monoculture plantations. A survey in part of the Indian Eastern Himalaya, found that only 5% of the landscape provides suitable habitat for the three large-bodied hornbill
species (Naniwadekar et al., 2016), while 37% of the landscape was suitable for the smaller Oriental Pied-Hornbill, that is more of a generalist, common in human-modified and secondary forests. Local hunting poses a substantial threat to these three species, especially in some states of North-east India in the Eastern Hima
layan region (Datta, 1998; Naniwadekar et al., 2015a, 2016). Hunting is mainly for their casques and tail feathers, which are used as adornments by local communities, for food, and fat for its perceived medicinal value and for polishing guns (Naniwadekar et al., 2016).
The Great Hornbill and Wreathed Hornbill have been locally extirpated from some sites in Arunachal Pradesh (Naniwadekar et al., 2015a). There is some evidence from a few studies that hunting may pose a greater threat to hornbills than habitat loss and degradation (Naniwadekar et al., 2015a in India, Holbech et al., 2018 in Ghana). Several studies have shown that hornbills continue to persist and breed in highly human-modified and fragmented habitats in the Western Ghats (Raman and Mudappa, 2003; Mudappa and Raman, 2009; Pawar et al., 2018; Pawar et al., 2021), where hunting levels are low. Hornbill densities are known to be influenced by the
availability of fruit resources, disturbances and nest-cavity availability (Kinnaird et al., 1996; Datta, 1998; Marsden and Pilgrim, 2003; Raman and Mudappa, 2003).
The few Protected Areas (PAs) that cover a limited area in the Eastern Himalaya region remain the main strongholds for these hornbill species. Currently, density estimates for hornbill species are available from only three Protected Area (PA) sites which are less disturbed with low human populations (Dasgupta, 2012; Naniwadekar and Datta, 2013; Shukla et al., 2016). To obtain a more reliable understanding of the global population status and trends of these threatened hornbill species, it is necessary to obtain reliable density/abundance estimates from across the species’ range.
The northern West Bengal landscape in the Eastern Himalaya forms the westernmost part of the global distributional range of the
Wreathed Hornbill and Rufous-necked Hornbill (Poonswad et al., 2013). This region has high human population densities compared to other parts of the Eastern Himalaya (in North-east India) and has had a long history of human settlement and forest conversion to tea estates and forest plantations in the last 100-plus years (Ghosh and Ghosal, 2019). Hunting pressures here are relatively much lower than in most parts of North-east India, though there are reports of chicks being poached from nests, primarily of the Oriental Pied-Hornbill, from some locations in north Bengal (Anonymous, 2023; Ganguly et al., 2022). The recent State of India’s Birds report
(2023) also assessed that the Rufous-necked Hornbill and Wreathed Hornbill are of high priority for conservation in the Indian Eastern Himalaya, which is part of a global biodiversity hotspot.
In this study, we comprehensively sampled Buxa Tiger Reserve (a highly fragmented and human-modified PA) to obtain density estimates of four hornbill species, making it possible to estimate abundances. Abundance information for forest hornbill species is often lacking due to the lack of representative sampling in tropical hilly forests and most studies are able to cover limited areas spatially. Previous studies have estimated hornbill densities from PAs with low human pressures (Dasgupta and Hilaluddin, 2012; Naniwadekarand Datta, 2013; Shukla et al., 2016). Abundance information is critical for assessing the species’ conservation status and monitoring
populations.
We report the abundances of four hornbill species (Great Hornbill, Wreathed Hornbill, Rufous-necked Hornbill and Oriental Pied-Hornbill) and the relationship between Oriental Pied-Hornbill encounters with forest structure, elevation, fruit availability and human disturbance in a densely populated, human-modified fragmented PA.

2. Methods
   2.1. Study area
   We conducted our study in Buxa Tiger Reserve (BTR; 89◦23’–89◦53’ E and 26◦34’–26◦46’ N), which lies in the foothills of the Eastern Himalaya of West Bengal, India. BTR encompasses an area of 760 km2 (Bhaskar and Rai, 2016, Tiger Conservation Plan) and is part of the Eastern Himalaya Biodiversity Hotspot. BTR’s northern boundary runs along the international border with Bhutan and the eastern boundary is shared with the state of Assam. The main habitat types are tropical semi-evergreen and moist deciduous forests with some areas of mixed species plantations. Most of the reserve lies in plains, but the northern parts are hilly. The altitude ranges from 65–1750 m above sea level. Many perennial rivers and streams flow through the reserve. The reserve has immense ecological and
   geomorphological significance and rich floral and faunal diversity. Over 350 bird species have been documented in BTR and it is a designated Important Bird Area (BirdLife International, 2023). BTR is known for its five resident hornbill species: Great Hornbill (Buceros bicornis), Oriental Pied-Hornbill (Anthracoceros albirostris), Indian Grey Hornbill (Ocyceros birostris), Wreathed Hornbill
   (Rhyticeros undulatus) and Rufous-necked Hornbill (Aceros nipalensis). The Indian Grey Hornbill is usually seen near human habitation, agricultural areas and forest edges. It has been reported from within Buxa TR (eBird data), however we have not detected this species within BTR. BTR has 37 forest villages and is surrounded by 42 revenue villages and 34 tea gardens (Bhaskar and Rai, 2016, Tiger Conservation Plan). Various ethnic groups reside here (Das, 2005a) with livestock-keeping being an important source of livelihood in these villages.

Das (2005b) reported a high dependency of villagers in BTR on Non-Timber Forest Produce (NTFP) for their livelihood support. A recent survey shows that BTR residents are dependent on forest resources such as water, fuelwood and fodder for their household consumption (Pradhan et al. unpubl. data).
2.2. Field methods
2.2.1. Estimating hornbill densities and abundance
We used line transects and Distance sampling approach to estimate densities of four of the five hornbill species in BTR (Thomaset al., 2010). We gridded the entire landscape of 760 km2 into 44 (5 × 5 km2) grids, of which rivers and streams partly covered 25 grids and ten grids were in hilly undulating terrain. Each grid had three transects varying in length from 1.2–1.5 km spaced approximately 500 m apart from each other (Fig. 1). All the grids (24) that were covered in the first year were repeated in the second year. There were three additional grids that were sampled only in the second year (2020–21).
Two to three trained observers walked a single transect, each day from 0600–0700 hr onwards with an attempt to maintain a speedof 1.5 km/hr. In the higher altitude areas, transects started late, usually around 0730–0800 hr, as the access to transects was difficult.
In the winter, a few transects started a bit late due to dense fog in the early morning. We used elephant trails or patrolling routes used by forest department staff for the transect surveys. The parameters recorded in both years include: 1) hornbill species; 2) flock size; 3) time of sighting; 4) activity (perched, foraging, call and flight); 5) perpendicular distance from the observer to the bird or observer to the centre of the observed flock (distances were measured for direct sightings only). We used rangefinders (Bushnell Trophy Rangefinder) to obtain perpendicular distances. The team walked transects over two non-breeding seasons of 2019–20 (September 2019 to March 2020) and 2020–21 (November 2020 to March 2021). Table 1 gives the details of the year-wise sampling effort.
2.3. Habitat variables: vegetation structure and composition
We used Point-Centred Quarter (PCQ) (Morisita 1954) to estimate vegetation structural variables like tree density, basal area, tree height and the tree species composition of the study area. We conducted the PCQs on the same transects for counting hornbills. We conducted vegetation surveys using PCQ method over 81 transects across the 27 sampled grids in the study area. The parameters recorded during PCQ included: 1) distance of the nearest tree in each quarter from the sampling point on the transect, 2) Girth at Breast Height (GBH) of the tree, 3) tree height, 4) tree species identity, 5) GPS coordinates of the sampling points. We used rangefinders to obtain distances to the nearest tree from each point and the tree height. For trees closer than 5 m, we measured the distance with a 30 m tape. We recorded trees with GBH ≥ 25 cm. For trees with multiple trunks below 1.3 m height, we measured the GBH of all the trunks separately.
While the PCQs enabled us to estimate tree density and basal area, to enumerate hornbill food plant densities and human disturbance, we counted the number of hornbill food plants with ripe fruits seen during the transect walks, within 10 m on either side of the transect for the entire length (belt transect). We also counted the number of cut tree logs/stumps seen within 10 m on either side of the transect. This provided a quantitative measure of disturbance/logging pressure as has been used in several studies (Eilu and Obua 2018; Karanth et al., 2006; Larpkern et al., 2009; Pyles et al., 2018).
2.4. Data analysis
2.4.1. Estimation of hornbill densities
We manually inspected the data to determine potential violations of distance sampling assumptions arising from heaping and outliers. We used multi-covariate distance sampling (Alldredge et al., 2007) to estimate densities of four hornbill species. Marqueset al. (2007) have used multiple covariate distance sampling to improve the reliability of density estimates for rare bird species. Owing to the paucity of visual detections of the three larger species (Table 2), we modelled the standard deviation of the detection function using body size as a categorical variable with two levels, one for the Oriental Pied Hornbill and the other for the three larger-bodied species (viz. Great, Wreathed and Rufous-necked Hornbills). Recent studies have found no significant differences in detection probability among larger-bodied hornbill species (Sriprasertsil et al. in review), and therefore, we feel that using a single level of the body size covariate to represent the three species is justified. Half normal and hazard rate detection key functions were used to model detection probability without the use of any adjustment terms. These models were compared with the intercept-only model using the Akaike Information Criterion (AIC). We used the chi-square test to test if the model fit the data well. We used the package ‘Distance’ in R for the analysis (Miller et al., 2019).
Table 1
Table outlining number of grids (5 × 5 km 2) and transects sampled, mean transect length, and total sampling effort (km) in the Buxa Tiger Reserve, West Bengal, India. Year Number of sampled grids Total number of transects walked Mean (range) transect length Total effort (km) 2019–20 24 71 1.5 (1.3 – 1.5) 106 2020–21 27 80 1.49 (1.2 – 1.5) 119

Consequences for the urban ecosystem

The encroachment of hornbills into cities affects both the birds and the urban environment.

• Human-wildlife interaction: The move creates new human-wildlife dynamics. Some residents welcome the hornbills, while others express concern about potential conflicts, such as hornbills preying on other birds’ nests.
• Ecosystem changes: The hornbills’ diet of fruits makes them important seed dispersers. Their introduction into urban environments could affect the spread of certain plant species, acting as “farmers of the forest” in an urban setting.
• Need for urban conservation: The hornbills’ shift underscores the importance of preserving and growing large, native trees in urban areas. Green urban development is crucial for supporting species that are adapting to a changing environment.