Subfossils of the Réunion ibis show that it was more robust , likely much heavier , and had a larger head than the African sacred and straw @-@ necked ibises . It was nonetheless similar to them in most features . Rough protuberances on the wing bones of the Réunion ibis are similar to those of birds that use their wings in combat . It was perhaps flightless , but this have not left significant osteological traces ; no complete skeletons have been collected , but of the known pectoral elements , only one feature indicate reduction in flight capability . The coracoid is elongated and the radius and ulna are robust , as in flighted birds , but a particular foramen between a metacarpal and the alular is otherwise only known from flightless birds , such as some ratites , penguins , and several extinct species . As contemporary accounts are inconsistent on whether the solitaire was flightless or had some flight capability , Mourer @-@ Chauvire suggested that this was dependent on seasonal fat @-@ cycles , meaning that individuals fattened themselves during cool seasons , but was slim during hot seasons ; perhaps it could not fly when it was fat , but could when it was not . However , Dubois specifically stated the solitaires did not have fat @-@ cycles , unlike most other Réunion birds .