 Subfossil remains and remnants of the birds that were brought to Europe in the 17th century show that they were very large birds , up to 1 m ( 3 ft 3 in ) tall , and possibly weighing up to 23 kilograms ( 51 lb ) . The higher weights have been attributed to birds in captivity ; weights in the wild were estimated to have been in the range 10 @.@ 6 – 21 @.@ 1 kg ( 23 – 47 lb ) . A later estimate gives an average weight as low as 10 @.@ 2 kg ( 22 lb ) . This has been questioned , and there is still some controversy . A 2016 study estimated the weight at 10 @.@ 6 to 14 @.@ 3 kg ( 23 to 32 lb ) , based on CT scans of composite skeletons . It has been suggested that the weight depended on the season , and that individuals were fat during cool seasons , but less so during hot . 
