Written by: Lucy Kemp of Mabula Ground Hornbill Project
After the storm has passed, I lay in my tent in Old Oyo National Park, Nigeria, listening to the dripping vegetation and the pre-dawn noises. A very familiar, deep booming call drifted across the grassland in the quiet of first light, before the clouds of tsetse flies could start their deafening whine and before the chatter of the rest of the birdlife began.
The sound belonged to the under-studied, poorly understood northern or Abyssinian ground-hornbill.
The other thunder bird, the southern ground-hornbill, is starting to become a popular focus of wildlife photography and articles highlighting its plight as an endangered species. It is in decline over most of its sub-Saharan range and is now the focus of much research. Very little is known of about the biology of its northern cousin, or if it too is in decline.
As its old name suggests, Abyssinia, or modern day Ethiopia, forms part of its range but it is also found in the dry savannas east to Senegal and south to Uganda and Kenya.
From their call, their diet and their appearance from the neck down, you would have difficulty telling the difference between these two species. One look at their face though and all is revealed.
The Abyssinian ground-hornbill wears make-up! An attractive deep-yellow swatch on their bill that is probably applied by rubbing this against their preen gland at the base of their tail. The southern cousins prefer to go without. The Abyssinian ground-hornbill also has a casque on top of the bill that looks like a cut-off piece of hollow horn. No-one really understands the purpose of this casque but it has been thought to be for display, maybe primarily of age and sex, as it grows to the same mature size and structure in both sexes but is slightly smaller in females.
For both species, you can tell the sex of the birds by looking at the bare skin around the throat and the eyes. In the female Abyssinians, the skin is entirely a rich lapis lazuli blue, while the males more resembles the southern ground-hornbill’s with their all-red facial skin but, being the showier of the two species, the Abyssinians cannot resist a little of the lapis lazuli themselves. The Abyssisian ground-hornbills show their sexual colouring from a very young age, while the southern ground-hornbills keep this hidden until they are much older, juveniles starting out with a standard cream then yellow/orange colour until they become red (and part-blue for females) at about four years old. This is a way of southerns remaining within the safety of the social group for longer; especially if you are a young female and cannot remain within your natal group for long before the alpha male kicks you out. It’s scary out there as a juvenile on your own roaming the savannahs and so it is probably better to look like your brothers for as long as possible.