 The white plumage and pink facial skin of adult American white ibises are distinctive . Adults have black wingtips that are usually only visible in flight . In non @-@ breeding condition the long downcurved bill and long legs are bright red @-@ orange . During the first ten days of the breeding season , the skin darkens to a deep pink on the bill and an almost purple @-@ tinted red on the legs . It then fades to a paler pink , and the tip of the bill becomes blackish . It is difficult to determine the sex of an adult American white ibis from its external appearance , since the sexes have similar plumage . However , there is sexual dimorphism in size and proportion as males are significantly larger and heavier than females and have longer and stouter bills . A study of the American white ibis in southern Florida yielded weight ranges of 872 @.@ 9 to 1 @,@ 261 g ( 1 @.@ 924 to 2 @.@ 780 lb ) for males and 592 @.@ 7 to 861 @.@ 3 g ( 1 @.@ 307 to 1 @.@ 899 lb ) for females , with average weights of 1 @,@ 036 @.@ 4 g ( 2 @.@ 285 lb ) for males and 764 @.@ 5 g ( 1 @.@ 685 lb ) for females . The length of adult female and male birds ranges from 53 to 70 cm ( 21 to 28 in ) with a 90 to 105 cm ( 35 to 41 in ) wingspan . Among standard measurements , American white ibis measure 20 @.@ 5 – 31 cm ( 8 @.@ 1 – 12 @.@ 2 in ) along each wing , have a tail measurement of 9 @.@ 3 – 12 @.@ 2 cm ( 3 @.@ 7 – 4 @.@ 8 in ) , a tarsus of 6 @.@ 75 – 11 @.@ 3 cm ( 2 @.@ 66 – 4 @.@ 45 in ) and a culmen of 11 – 16 @.@ 9 cm ( 4 @.@ 3 – 6 @.@ 7 in ) . 
