I was at work today and four ducklings that couldn't be more than a day or two old were wandering outside my office for a few hours. I brought one home because my wife and I have always talked about raising a duck, but now there are actually logistics to deal with. I have the right food for him and have set him up with plenty of water and a nice place to nap, but if anyone has ever had a pet duck, I would love some pointers.
I remember raising ducks and chicks when I was in 2nd grade. You need food. I don't remember exactly what we fed them. But they were these little seeds. And they need lots of warmth. And lots of water - to drink and swim.
Thought this was a funny comment. I'm sure you have already searched the internet, but here is a site that looks pretty helpful: http://www.howtodothings.com/pets-and-animals/a3728-how-to-raise-a-duck-as-a-pet.html
Are you sure it’s a duckling, and not a gosling or a swanling of some sort? You might consider sending some photos to someone at the Houston Audubon Society to see if they can give you an exact species ID. That would give you a basis for knowing, for instance, whether it is a species that naturally lives alone or forms colonies in the wild. They can probably also give you much better information about care than you can get off the internet.
My parents raised ducks in their backyard in Houston for some time. (We have a giant secluded bayou and forest in our backyard) They were full grown ducks, but eventually the racoons or coyotes ate them. This happened different several times, and thus my parents stopped buying ducks. We just left them outdoors to swim the bayou, so we didn't actually keep them inside or house or anything. There is this feed store that sells duck food in the Montrose area, near the Walters on Washington music venue. You can call them for more information and tips, as that is where we bought our ducks. It looks like what you have is called a "wood duck." These are the wild variety type that move from place to place. They also fly and live in trees. http://en.wikipedia.org/wiki/Wood_Duck We still see these in our backyard from time to time usually in the mornings. So I guess if you go to the bayou in your area in the morning you can release it join a family of wood ducks. The ones we used to buy and raise were the white, peking duck type variety.
Good luck. My little girl and I tried to rescue a baby bird that one of the cats had brought in to no avail. Twinkles was dead by morning. Your duck looks a lot more mature than Twinkles did...