Examples from the Web for flightless
Flightless rails have apparently developed in the absence of predation.The Avifauna of Micronesia, Volume 3|Rollin H. Baker
The flightless great auk, which at one time was common along the north Atlantic coast, belongs to this family.
It was probably a poor flier, though not flightless, as Fulica chathamensis was.Extinct Birds|Walter Rothschild
Here we find the flightless Apteryx and a flightless goose now extinct, also the extinct Moa.
There are flightless birds, but they all live in climates in which they can exist at all seasons.The Migration of Birds|T. A. Coward