| Adult | |
 | white quills on outer primaries forming white panel |
 | narrow bill yellowish brown tip |
 | gray toes covered with chalky excrement |
 | gray skin on featherless head wrinkled neck |
| Juvenile | |
 | black skin on head black tip on mandibles (changes to yellowish brown) |
 | duller black than adults |
| Nestling | |
 | Buff colored long, thick, black beak |