The breeding behaviour of the Indian Grey Hornbill – An Inside View by Ajay Gadikar

This is an article about the breeding behavior of the Indian Grey Hornbill (Ocyceros birostris) observed at the bio-diversity park in the Residency area in Indore city.


I have been observing the Indian Grey Hornbill (IGH)   in the Residency area of Indore since the last 5 years. I always get mesmerized when I see these birds, firstly due to their very peculiar casque (horn) over their bill and secondly their undulating type of flight.


The Residency area in Indore is full of old fig trees like Pipal, Banyan, Gular and also the Jamun. These trees are like magnets which attract the hornbills since these figs comprise most of their diet. I used to see them mostly in the morning moving high up in the canopy as they are mostly arboreal in nature.


Their breeding period, which is from March to May-Jun, coincides with the ripening of fruits in all the fig trees. During this period there is sufficient food available in the form of fruits of these trees which helps the parents to fulfill the demands of the growing chicks.


Outside their breeding season these birds are frequently seen in the morning and evening feeding and indulge in various social interactions like bill grappling, aerial jousting and erratic chases in the higher canopy of trees.

I would like to share with you my experience with the  nesting behavior of these birds as recorded and unveiled by using a camera.


I had watched a natural hole on a Gulmohar tree which a hornbill pair had used for nesting purposes in the  last season. With  the help of the forest department a CCTV camera, capable of zooming in and out was installed 5 meters away from the nest to record  the whole breeding cycle almost for a period of 3 months. A 11 minute documentary film “UDAN” was made based on the important footage obtained from the 24×7 recording. This film was inaugurated by the Chief Minister of Madhya Pradesh.


I would  like to  share the following details about the general breeding behavior of the IGH.


Their nesting is very unique. When it is time to lay eggs, the female hornbill enters the hole of the tree trunk and does not step out into daylight again, until it hatches the eggs and the babies are at least one and half month old, which means she remains under the nest cavity for 60 to 65 days.


The female starts to seal the nest cavity once she enters inside. Only a narrow slit of size 3-4 cm by 7-8 cm remains open, from where the male feeds the female. The material used to prepare the wall of the nest cavity are mud, fruit pulp and her own droppings. The female now solely depends on the male for her food. The male fetches fig and berries from nearby trees and feeds the female, approximately once in an hour throughout the day. Most of the feeding took place early in the morning. The male carries 5-8 berries and 1-2 insects in his mouth in one go and regurgitates them one by one into the female beak by clinging to the nest.


Once inside the nest, the female lays the eggs and incubates them. Soon the chicks come out of the egg. At the same time the female also undergoes complete moult, by shedding all her feathers.  This is a really vulnerable time for the family as the female bird cannot fly and cannot feed the chicks, the family is totally dependent on the male bird. If something happens to the male bird and if he dies, then the entire family can die due to starvation.  


During the nesting the male bird feeds the female and the chicks with a variety of fruits, and also small insects, grasshoppers, lizards etc. It travels long distances in search of food. The fruits are held in its throat and when it reaches the nest it regurgitates the fruit one by one from its pharynx to its beak and feeds the female which does not come out and receives the feed by putting its beak out. When the chicks are sufficiently grown the female breaks open the nest and comes out and both parents feed the young ones.


These birds use the same tree and nest repeatedly  and come back to the same place in their next breeding cycle.


The camera study for  3 complete months of the Hornbill nesting was done first time ever and it confirmed many of the points which scientists have written in journals over the years.


The main findings that come out of the CCTV camera study were:


Constituents of Diet: The major plant species that constitute the food of the hornbills during the nesting period was Pipal, forming roughly 40% of its diet, Banyan, which constitutes 20% of its diet, around 20% was insects and rest 20% other fruits. Interestingly in the video the male hornbill was seen feeding pieces of dry chappaties and biscuits which was altogether a new finding.


Moulting of feathers by the female: The female has been seen dropping many feathers from inside the nest which confirms the theory that she sheds her old feathers and comes out with new feathers. We have collected those feathers and sent them to BNHS, Mumbai and have received confirmation from the scientists of BNHS  regarding the same.


Closing of wall by the Chicks: It was remarkable to see that after the female had left the chicks  closed the nest wall again leaving a small slit open as their mother had done earlier with the help of mud, saliva and fruit pulp. It was amazing to see them closing the hole and I kept pondering that who had  taught them this and how.


Study of Excreta: The excreta collected and examined contained undigested seeds of various fruits and berries delivered to the female and chicks by the male hornbill. I collected and identified approximately 20 different types of seeds. Some undigested insect  body parts were also collected beneath the tree where the nesting was done. Undigested body parts like feathers, eyes etc. of grasshoppers and other insects were collected. The male had brought these insects to provide nutritious and protein diet for the chicks.


Use of Bark: The female accepted numerous bark pieces provided by the male hornbill. Some bark pieces were thrown out by the female later, these bark pieces belonged to different trees species. I collected many such ejected bark pieces with fresh excreta on it. These dry bark pieces are used to absorb much of the water content from the fecal matter. They probably play a vital role in maintaining humidity inside the nearly sealed cavity nest and providing a cleaner environment inside the nest.


Birds visiting the Nest: Rose Ringed Parakeets were the most curious and would often visit daily and try to peep inside the cavity. The camera footage also showed the Common Myna and Oriental Magpie Robin among the visitors to the nest. Squirrels were also keen to look inside the nest and used to visit the nest many times in a day.


Interesting activity of chicks was also recorded. They did not want to come out of the hole as they found it very comfortable inside the nest with their parents feeding them. But their parents enticed  them by holding the food in their beak and encouraged them to come out of the nest to fetch it and face the world.


An important message which emerged from observing the complete nesting of the IGH:-

The female trusts the male blindly and the male does not commit breach of trust! A lesson for  mankind!
The documentary film on the IGH life cycle was prepared with the help of funding from the M.P. Ecotourism board and was inaugurated by the Chief Minister at the State Wildlife Board Meeting. The 11 minute film was screened at different cinema halls in Indore during the interval of regular movie shows and was also distributed for viewing in many schools of Indore.