Most of us dream of having both aquatic animals (seals, penguins, otters, sea lions...) and flying birds in the game someday. However, if we had to choose between aquatic animals or flying birds, what would you prefer?
For me, it would be the aquatic animals. When I go to a zoo, I love seeing the penguins and other aquatic animals. They are usually more active and funny to watch. However, birds are usually hard to see because they are just hidden on the trees.
Allow me to respectfully and enthusiastically respond to that. All of those aquatic animals you mentioned, are amazing, they can also be found in Aquariums. Granted, many zoos have them, however there are a large number of zoos that do not. Sea lions are no found in many zoos especially on those zoos with tropical and sub tropical climates. Otters are somewhat a common staple of zoos, especially in recent times, since they are very playful and everyone loves them. Seals are a rarity in zoos, you would have to hand pick the zoos in order to justify their existence on them. Penguins are somewhat common if we are referring to species found in tropical climates, go the Aquarium route and bring the big guns of King and Emperor Penguins, and line up your pocket, because their exhibits are extremely expensive to built and maintain (source myself, being a part of the zoo design industry for decades) This is the reason why you would not find them often in zoos, even Aquariums for that matter, tens of millions are needed to built exhibits for them.
Now in reference to your point about birds, have you ever heard of bird watchers? (I'm not one, lol) however this individuals are a good representation of what every zoo visitor should behave like. It takes patience in an aviary to spot certain bird species, as you said they are often found in branches, soaring thru the aviaries, visitors need to take their time, enjoy them, walk softly and be gentle. A screaming kid with a balloon, running thru an aviary, is a perfect example of how not to see a bird.
However for the most part, birds in zoos are extremely easy to spot, so much so, that they often used as ambassadors or focal points of zoo entrances. A Condor would be extremely easily to spot, an individual would have to be blind not to see it. An Indian Hornbill would be a sight, A pelican can be quite intimidating if close enough. Vultures add life to any African Savannah exhibit. Look down into ponds and lakes you will see a multitude of ducks, herons, storks, etc. In short birds are some of the easiest animals to spot in Zoos, contrary to seals or sea lions, that if it happens to be nap time, you will be out of luck. Penguins are also birds.
