Comparison between flying birds and flightless birds

Flying birds (Carinatae)	Flightless birds (Ratitae)
1.         Usually small in size	Usually large in size
2.         Well developed wings	Poorly developed wings
3.         Interlocking mechanism in feathers is present	Absent
4.         Tail quills are present	Absent
5.         Oil gland is present	Absent
6.         Well developed flight muscles	Reduced fight muscles
7.         Keel is present in breast bone	Absent
8.         Short legs	Long and stout legs
9.         Copulatory organ is absent in males	Present
10.     The young are naked without feathers (altricious)	The young are with feathers (precocious)
11.     Cosmopolitan distribution (found everywhere)	Discontinuous distribution
12.     E.g. Crow, Columba, Parrot etc	Struthio, Kiwi, Penguine etc