A lot of fiction has pterodactyls behaving as giant birds. I believe in Jurassic World, they showed pterodactyls nesting on skyscrapers. In lots and lots of dinosaur fiction, pterodactyls are commonly shown building nests and keeping their babies in tall trees. It's noteworthy that we have a weaker fossil records on pterodactyls than other dinosaurs because their bones were less likely to survive long enough to become fossilized. Only in the 21st century did paleontologists find confirmed pterosaur nests and these nests are on the ground. Lustria does not have to follow 21st century paleontology. Who knows, in twenty years we may be find evidence that some pterosaurs nested in trees. What about Terradons and Ripperdactyls? Do we go with the current science and have them nest on the ground or do we go with popular fiction and have them build their nests in high places. Perhaps there is another dimension I am missing, but the main advantage of nesting high up is that eggs or hatchling are theoretically more protected from egg stealing or baby eating predators. The main disadvantage of nesting high up is there is the chance of gravity taking out eggs or hatchlings. You need a really secure tree to support the weight of one adult pterosaur and a bunch of hatchlings. That's assuming the mother tends to the eggs. If the mother and the father raises the young together, you need a branch that can support two adult Terradons. More if they raise their young as a flock. Lustria has nasty storms during the monsoon season. If Terradons/Ripperdactyl hatchlings grow really fast, they can be hatched and raised to being able to fend for themselves before high winds knock nests down but if that is not the case you need high elevation nesting locations that can withstand the gravity of several adult Terradons and withstand high winds. I suppose a nest on the ground can accidentally get stepped on by a large land animal, and a nest in a tree can accidentally get downed if the tree gets chopped or knocked down for some reason unrelated to the Terradons. If it matters, I am assuming that Terradons primarily eat fish and are relatively light eaters. I am assuming Ripperdactyls primarily eat land animals and have practically bottomless stomachs. Wild Versus Domesticated/Tamed Flyers If Terradons and Ripperdactyls like to nest in high places, I am guessing that Skinks construct stone towers and entice these creatures to nest on them. The stone towers have stairs or ladders for Skinks to ascend that can be closed off to prevent egg stealing predators from using them. The stone towers are sturdier and safer than most trees. If Terradons and Ripperdactyls normally nest on the ground, I am guessing that Skinks stone structures with open ceilings. This lets the Terradon parents fly in and out of their nests, but it provides the nests a modicum of protection against flood waters, predators, and being accidentally stepped on. Either way, Skink Terradon and Ripperdactyl riders would probably set up rest areas, watch towers, and/or waystations throughout the jungles of Lustrias. These structures may or may not double as artificial nests or they may have no relation at all to actual nests. A trained Terradon or Ripperdactyl could be trained to sleep and rest anywhere a Skink wants without a need to copy nesting behavior. I am assuming that Skinks would prefer to keep Terradon bases near their main living and work areas (for convenience). I assume they prefer to keep Ripperdactyl bases as far from their main areas as possible (for safety).