Struthio camelus (ostrich) is gregarious polygamous and omnivorous flightless bird, oil glands preen gland are absent. Syrinx is also absent. Casuarivs sp. is flightless bird. To head is beautifully coloured due to presence of helmet like horny casque. The preen gland and syrinx are absent. - Apteryx australis (kiwi) is small terrestrial flightless bird beak is long with nostrils near the tip. Oil glands are present but syrinx is absent. - Oil glands are present in Tinamus but syrinx is absent.