The African Openbill (Anastomus lamelligerus ) is a species of stork from the family Ciconiidae. It is widely distributed in Sub-Saharan Africa and western regions of Madagascar. This species is considered common to locally abundant across its range, although it has a patchy distribution. Some experts consider there to be two sub-species, A. l. lamelligerus distributed on the main continent and A. l. madagascariensis living on the island of Madagascar. Scientists make the difference between the two sub-species due to the more pronounced longitudinal ridges on the bills of adult A. l. madagascariensis.The Asian Openbill (Anastomus oscitans ) distributed in Asia is the African Openbill’s closest relative. The two species share the same notably large bill of a peculiar shape that gives them their name.
The African Openbill is a stork measuring 80-94 cm and weighing 1-1.3 kg. The species does not exhibit any major sexual dimorphism, although the males are slightly larger than the females and have a longer and heavier bill. The adult bill is between 135-196 mm in length, brownish in color and has a gap between the upper and lower mandible. This gap is non-existent in juvenile birds and develops as the bird ages. It is because the two mandibles of the beak only meet at the tip and not in the middle that this stork genus received the name of “openbill”.
The adult plumage is overall black with iridescent green feathers on their backs, coverts and abdomens. The juvenile plumage is usually less vibrant and browner in color with the feathers of the underparts having pale tips. The legs and feet are black. The eyes are grey with grey lores and no distinct coloration of the eye-ring.
These storks are smaller in stature than most of the other species in their family which allows them to be much more agile in the air. This agility can be observed during their descents from high altitudes as they often perform steep dives and remarkable acrobatic manoeuvres. During their migration flights, the African openbill storks will use sustained flapping flight with an average wing flap rate of 200-210 flaps/minute. They will also often soar on the thermals when commuting to and from distant feeding areas. This allows them to travel long distances to obtain food without expending too much energy. In flight, these birds have their necks and head extended and their long, broad wings are spread out and perfect for soaring and gliding on the air currents.
Some African Openbill population are trans-equatorial migrants. Timing their migration to arrive in West Africa for the start of the dry period. They migrate in flocks and most of the reason and organisation behind these movements remain unknown. Some populations migrate while others are residents, migration in African Openbill highly depends on the weather conditions.
