Since several weeks, Burgers’ Bush has had a colourful addition. No less than three wrinkled hornbills roam freely in the indoor tropical rainforest. Burgers’ Zoo already has experience with this impressive bird species in the Bush, however, that was quite some time ago. It is also always a question of waiting and seeing how individual animals react to a completely new environment—all in all, a good reason to try again.
The decision for three males
In consultation with the wrinkled hornbill's studbook keeper, Burgers’ Zoo decided to introduce three males to the Bush. Due to a shortage of females in the European breeding programme, these males have no short-term prospect of a partner. Besides, all three animals were temporarily living alone in the zoo they lived in. One of the birds is from Burgers’ bird department, where his female, unfortunately, died a few months ago. The two other birds come from Ouwehands Zoo and Bird Park Avifauna, both in the Netherlands. Studies of wrinkled hornbills in the wild have shown that these birds live in groups outside the breeding season. They are quite social animals and it seems they feel less comfortable without their kind.
A carefully planned introduction
To introduce three new birds to one another in a large animal enclosure like the Bush, the team of biologists and zookeepers carefully prepared the process and planned it step by step. The birds were first place in three separate large cages in a quiet location in the Bush, so that they could get used to both their new environment and each other, without having to share enclosure. The birds couldn't see each other, but they could hear each other. The hornbills spent one night in the cage, so they could quietly observe their surroundings, eat and acclimatise. When the doors were opened, it took a while for the first courageous bird to cautiously step out of its cage. The male from Burgers’ bird department was quite happy in the familiar cage. Eventually, however, all the birds ventured out and carefully began exploring their environment. For the first few days, zookeepers and guides monitored the birds and their behaviour almost by the minute. Two things were particularly important: that the birds were able to find food within the foreseeable future and that they did not remain on the forest floor all the time, but that they would also be spotted higher up in the trees. In their previous habitats, these birds were not able to make long flights. So, the first days were spent rehearsing and rebuilding the muscle power in their wings for longer flights.
Scavenging for food
During the first few days of their release, natural foods were put in the introduction cages, and the Burgers’ Zoo hornbill returned to his introduction cage at night to eat. Zookeepers also set up several permanent feeding locations throughout the tropical rainforest. Luckily, the birds quickly found these locations and all three were soon observed eating there. The Bush has many natural food sources, such as various types of fruit, and the hornbills are now showing natural scavenging behaviour, and, in addition to the feeding locations, they are also finding the fruit on the trees. When you are walking through the Bush, it is worthwhile taking a good look at the treetops to see if there happens to be movement there. Maybe you will witness a wrinkled hornbill skilfully work some figs into its large beak!
Territorial behaviour
It is unknown whether the males will claim their territory and show territorial behaviour to each other. Despite the surplus of food sources in the Bush and the absence of females to be fought over, it is impossible to predict with one hundred per cent certainty how the animals will behave amongst themselves. For the time being at least, the animals are not showing any aggression toward each other.
The birds from Ouwehands Zoo and Bird Park Avifauna seem to appreciate each other's company and often visit each other. Both birds are often spotted in each other's vicinity, usually still with up to a metre between the two animals. All three birds have been observed vocally communicating with each other. As we expected, any territorial behaviour seems to be out of the question for the time being, and, fortunately, no aggressive behaviour towards the other species in the Bush has been observed at the time of writing.
Some weeks later
At present, all three birds make long and often high flights through the forest. The individual animals have their preferences for certain locations and parts of the Bush where they are more often spotted by the zookeepers. The somewhat hesitant behaviour shown during the first few days has made place for more familiar behavioural patterns. The birds seem visibly more accustomed to their new environment and are now starting to discover what this varied environment has to offer. In doing so, the hornbills are showing more and more natural behaviour. In the autumn, the Bush is always cut back considerably. This year the gardeners have pruned the plants to such an extent that the hornbills—and other bird species—can now make long flights above the treetops.
Will they live happily ever after?
The first signs are positive, but it is still too early to state that it has been a successful introduction. There are too many external factors that can play a role in this. Will the hornbills continue to tolerate each other? Will their behaviour towards the other animals in the Bush change? What will they focus their inventive and intelligent behaviour on in future? These are all questions yet to be answered, and there is no crystal ball to predict the future. Zookeepers and biologists will continue to closely monitor the behaviour of these large birds. So far, visitors can continue to enjoy this wonderful natural enrichment of the tropical rainforest ecosystem to the fullest. Let's hope that the wrinkled hornbills can be admired in the Bush for years to come!
