Marabou stork of any landbird, to rival the Andean condor; more typically, however, these storks measure across the wings, which is about a foot less than the average Andean condor wingspan and nearly two feet less than the average of the largest albatrosses and pelicans. Typical weight is , unusually as low as , and length (from bill to tail) is . Females are smaller than males. Bill length can range from . Unlike most storks, the three "Leptoptilos" species fly with the neck retracted like a heron. The marabou is unmistakable due to its size, bare head and neck, black back,
What Bird is That? all-time best seller in Australian natural history and is still in print today. While sales and stature of Cayley’s original collection continued to grow, the prolific artist and ornothologist Cayley was working on a much more ambitious project – his so-called “big bird book”. From about 1918, he was creating illustrations of subspecies, plumage stages and eggs (now lost) of all known Australian birds. The project was incomplete at the time of his death in 1950, although the illustrations were all but finished. The ornithologist Terence Lindsey revived Cayley’s plans in the 1980s, creating the last and most significant revision