A penguin is, as most people know, a flightless bird which lives mainly in colder climates of the southern hemisphere. Some species do live as far north as the equator, but only in areas near cold ocean currents.
These birds are very well adapted to swimming. Some species can make dives over eight hundred feet deep. Along with this comes the ability to hold their breath for a very long time. The Emperor penguins can hold their breath for up to eighteen minutes.
Most species of penguins feed on crustaceans such as krill, fish, and squid. The penguins catch and swallow their prey underwater.
The penguin's bones are rather solid compared to the bones of flight birds, thus meaning less energy is required to dive.
"The wings lack flight feathers and cannot be folded; in use they form flat, scimitar-shaped paddles, which propel the birds rapidly through the water." Quote from Birds, Their Life, Their Ways, Their World, on page 178.
The ways penguins nest vary greatly. Little blue penguins nest in burrows, Gentoo penguins make nests of plant materials, and King and Emperor penguins build no nest at all, the males incubate the eggs under a flap of skin and the eggs rest on the feet.
(I have chosen todo bulbuls for my flight bird.)
The bulbuls feed on vegetation such as berries, fruit, and buds. A few species eat insects.
The bones of these and other flight birds are hollow, which makes flying easier because less weight has to be lifted. The inside of the bones have struts for strength.
The bulbuls wings are short and rounded. This makes flying a bit harder, so few birds of this species migrate.
Bulbuls build their nests in the forks of trees or bushes. The nests are built of materials such as twigs, leaves, spider's webs, and other materials and lined with grass.
As you can now see from this report, penguins are very different from flight birds.
Resources
The Encyclopedia of Birds
Birds, Their Life, Their Ways, Their World