Kargarok

Making their first, appearance in The Wind Waker, Kargaroks were bird-like creatures that Link faced frequently in his quest.

The name "Kargaroc" is most probably derived from "Roc" (as in Roc's Feather), an item featured in various games in the Zelda series.

Wind Waker
Kargarocs (as their name was spelled in TWW, see Nintendo Gallery) were used by Ganon for surveillance and transportation of other monsters, such as moblins, across the sea. The Kargarocs were easily defeated when roosting, and were also susceptible to arrows (and cannon fire) when airborne. Often, Link could glean rare Golden Feathers from the tails of defeated Kargoroks, which fetched a nice price when presented to a certain guard on Dragon Roost Island. An interesting fact is that these creatures bear a resemblance to the Helmaroc King, the giant bird that kidnapped Link's sister, Aryll.

Twilight Princess
In Twilight Princess, Kargaroks have two distinct incarnations. The first is a common enemy in Hyrule Field, which attempts to knock Link off of Epona. The other version is it's Twilight form, the Shadow Kargarok, where it is recognizable save the head, which is ragged and open to look like a horn. It is very easy to slay a Kargarok, as there are many possibilities. The quickest way, or most effective, (as this creature flies) is to shoot bomb arrows at it. The second easiest way is to shoot plain arrows, or when it gets close enough kill it with your sword. But most of the time, it is easiest to ingnore them, especially when you are riding Epona. The Twilit form (when you first enter Lake Hylia) is a little harder to defeat: the Twilit Kargarok that Midna eventually controls. Keep a distance from it, let it have some run way to charge at you, and when it comes close roll and quickly bite it. Once defeated, Midna takes control of it, and the adventure continues.