You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "why are birds such as kiwi and penguin unable to fly?" whose answer is through evolution.
Each document should contain about 30 words, and these documents should contain useful information.

Query: reasons why kiwis and penguins are flightless
Useful Output:

Doc 1: Penguins cannot fly because they have very short wings and proportionately heavy bodies.  Kiwis are the national bird of New Zealand and
Doc 2: Flightless birds can no longer soar into the skies, but they have developed unique features and abilities that enabled them to adapt and survive
Doc 3: The genetic evidence indicates that the ancestors of the king and emperor penguins, the two largest species, soon split off from the other
Doc 4: Kiwis' wings are way too small to hold them up. Penguins have much heavier bones than most birds. Ostriches and cassowaries are simply too big.
Doc 5: Ostriches, emus, kiwis, penguins, and cassowaries can't fly because their bodies have adapted differently to the environments they live in.