Grey (Tockus nasutus), Red (Tockus erythrorhynchus) and Yellow billed (Tockus flavirostris) hornbills have a unique and ingenious nesting strategy, involving remarkable trust and cooperation between a bonded pair of mating individuals. This bond is formed by prolonged and elaborate courtship displays involving gifts from the male enticing the female, to prove what a wonderful father he will be, as well as incessant head bobbing/ wing bowing and serenading from the tree canopy tops.
All three species belong to the “Tockus” genera which is derived from their distinctive territorial and courtship calls used to establish a monogamous pair bond which typically lasts one season – either by “head-down clucking” as seen in the Red and Yellow billed or “head-up whistling” practised by the Grey hornbill.
Once the pair has mated, following the first summer rains when there is adequate insect food and ample mud in natural pans and wallows, the male will set about sealing the female inside a natural tree cavity. This is achieved by plastering a mixture of mud, excrement and sometimes even millipede pieces (which act as a repellent) using their sturdy beaks like a brick layer’s trowel to incarcerate the female inside the woody chamber so that only a narrow-slit remains.
This keeps unwanted visitors out such as genets, snakes and other small predatory animals (which would see the eggs and chicks as a welcome meal) while still allowing the male access to deliver food to the female.
Furthermore, the female undergoes a rapid flight feather moult losing all tail and flight feathers which are then used to line the interior for insulation during the incubation period. At this point she’s completely reliant on the male’s dutifulness – hence, the strict initial dating guidelines!
By the time the chicks are half grown, the mother would have regrown her feathers so that she can assist the male, who by now cannot manage to feed the growing chicks by himself. The mother then breaks out and the tree hole cavity will be resealed by the oldest chicks, who are fed preferentially by the female which results in brood reduction – a strategy which ensures surviving chicks are strong.
As the chicks become accustomed to their increasingly cramped home, they would keep their tail feathers erect in an upward direction to save space, as well as to instinctively “potty train”, using their rapidly developing legs to clamber up to the slit and tidily aim their excrement out of the nest!
The comical courtship displays and incessant “to-ing and fro-ing” of insect laden adults to the nests can be seen all around Arathusa in the summer months. Hornbills are by no means the only interesting nesting bird at this time of the year but they are among the easiest to see, as they are commonly found alongside the roads in mature trees and sometimes even in the camp!