The Outlaws of Mars by Otis Adelbert Kline

AT JUNIA'S cry Jerry whirled around, then gave a low whistle of amazement. A monstrous thing was wading toward them across the narrow stream. As he gazed, it emerged upon the bank, a gigantic and hideous bird, fully forty feet in height.

Its long lean neck and scrawny body were leathery and bare of feathers. On its huge head was a waving crest of plumes. Its beak, which was four feet in length and two in width at the base, was hooked like that of an eagle. The short wings were covered with sharp spines in lieu of feathers. The long scaly legs were adaptable either for wading or swimming, and there were leathery webs between the toes, which were armed with immense, sickle-shaped talons.