When we got to GZ, we quickly realised that we were right under a Hadada roost tree. They left, loudly complaining about being disturbed.
The Hadada is a large (about 76 cm long), grey-to-partly brown species of ibis. Males and females are alike in plumage. It has a narrow, white, roughly horizontal stripe across its cheeks. This is sometimes called the "moustache" though it does not reach the mouth corners. The plumage over the wings has an iridescent purple sheen.
The bird has blackish legs and a large grey-to-black bill. The wings are powerful and broad, enabling quick take-offs and easy manoeuvring through dense tree cover.
It has an extremely loud and distinctive "haa-haa-haa-de-dah" call. The call is often heard when the birds are flying or are startled, or when the birds communicate socially, for example early in the morning in residential suburbs. While roosting they produce a single loud "haaaa". When foraging, their contact call is a low growl similar to that made by a young puppy.
Hadada ibises roost in groups on trees. They fly out in the mornings with loud calls and return in the evenings with regularity. They feeds on insects, millipedes and earthworms, using their long scimitar-like bill to probe soft soil. It also eats larger insects, such as the Parktown prawn, as well as spiders and small lizards. These birds also favour snails and will feed in garden beds around residential homes. They are particularly welcomed on bowling and golf greens because they are assiduous in extracting larvae of moths and beetles that feed on the roots of the grass.
Hadada have become very common in many African cities and tolerate the closeness of humans. They are able to judge the direction of gaze of humans and the speed of approach to decide their escape strategies. Hadada ibises have been involved in several bird-hits at airports in Kenya and South Africa.
Hadada are monogamous and pair bonds are thought to be maintained even outside the breeding season. Pairs begin breeding just after the rains. In the Cape province, they breed mainly from October to November. The nest is a platform of twigs placed in a tree. Both parents take part in incubating the clutch of three to four eggs for about 26 days after which the young are fed by the parents by regurgitating food. Many young birds die by falling off the nest. The ones that survive fledge in about 33 days.
https://en.wikipedia.org/wiki/Hadada_ibis