|Northern Bald Ibis|
|NBI in zoos|
|ex situ projects|
Northern Bald Ibis: breeding
Nest building starts in February and first eggs are laid in March-April. Clutch size 2-5 eggs and incubation takes 28 days. The chicks fledge at 43-47 days. Both parents brood and feed the chicks. The offspring and parents retain close contact. During autumn and winter the contact is reduced but the intensity of the parent-offspring relationship again increases at the beginning of the next breeding season.
The NBI is a colonial breeder nesting on cliff ledges and will also use artificial ledges. However the size and shape and covering of the ledges seem to be crucial. Nests are built of short branches and are compact and can be thick as 15-25cm. The inner layer is made of softer material as dry grass.
As eggs are laid at 2-day intervals and incubation starts when the first egg is laid, the chicks hatch on different days. Because of this age gap the older chicks are often stronger than the younger ones which may be lost due to starvation (passive sibling competition).Additionally there is an active sibling competition depending on the age of a nestling and displayed by all chicks during the age of 14-25 days. The aggressor pecks mainly on the hind head, sometimes at the neck and wings of its sibling and although hardly causing any injury this prevents the other chicks begging for food. This aggression is displayed only when one or both parents are at the nest. The aggression decreases rapidly after a chick gets older than 25 days and reaches a body mass of over 850g. If younger chicks survive this period of aggression they will gain weight very rapidly.