Plausibility of Hexapodal Aerial Megafauna

How plausible is a six-limbed flying animal roughly the size of hatzegopteryx to be aerial? In this case, an aerial animal will be defined as a creature that solely inhabits the sky. I will call the animal a dragon for simplicity.

The creature spends its entire life gliding through the air. The only time it spends on land is when it hatches and when it lays its eggs. At the end of these creatures' life, they meet with another dragon and engages in a fantastic mid-air mating display. Once the female has been fertilized she will seek out a suitable cliff or mountain. The cliff or mountain must be at a perfect altitude: high enough to jump off of and glide, and low enough so that there is suitable oxygen. Once the female finds a perfect location she will memorize it and begin a new search. The female will then spend the next few weeks collecting Tree-toppers, a fruit-like mass that grows at the peak of tree-like plants. Once the female has collected a sufficient amount and placed them at her nesting site, she lands above her nest and lays five to six eggs. Once the female has landed, she will never fly again. She spends her last few months of life caring for the eggs until they hatch. At which point she will wait for them to build their strength. Once the dragon hatchlings are strong and large enough to collect Tree-Toppers for themselves, they leap from their nest. These young dragons will spend the rest of their lives gliding through the air until they sense their imminent mortality, at which point the cycle repeats.

How plausible is it for this animal and its lifestyle to exist?

• Sorry if the question is unclear. I was in a hurry to type it as my laptop is close to dying. I will add a diagram of the animal once I can. – MintySoftboi Nov 25 '19 at 19:10
• Of interest, not a dupe: worldbuilding.stackexchange.com/q/56701/10851. This question and its answer discuss that if you want an endoskeleton and X-podal for X > 4, then you need to do an evolutionary split from the Real World(TM) a loooong time ago. – cobaltduck Nov 25 '19 at 19:22
• "I will call the animal a dragon for simplicity". Does this animal have any other dragon-like characteristics? If so, that would be relevant to its evolutionary path. – Snowshard Nov 25 '19 at 19:31
• if the creature flies for most of its life, why does it need limbs? They create drag, and take lot of nutrients to grow. – Bald Bear Nov 25 '19 at 19:58
• Dying after giving birth seems plausible (salmons), hardly ever landing seems plausible (common swift), but I would be worried that the size you intend is way out of range of probability. The energy needed to keep that much mass constantly airborn seems to be unreasonably high, especially if your dragons feed on fruit, not meat. Maybe it would be possible in a world with omnipresent strong rising air currents. – Mori Nov 26 '19 at 14:02

Its not unplausable, however there needs to be a reason for the creature not flying again.

Animals are very much living creatures, and all things equal - being alive tops being dead.

Also if these creatures have general intelligence there will be a learning period, this is often provided for by the parent/herd/pack. In the absence of the mother these creatures will need another source of education.

As for why the female dies.... The act of landing itself, or the act of nesting has to take an unrecoverable toll.

• The wings themselves are irrecoverably damaged by landing, locomotion, or nesting.
• The environment itself is deadly to adults, but the eggs/hatchlings require it/are adapted for it. eg: toxins slowly build up eating muscle mass in the adult, rendering it flightless.
• Exhaustion. It is too dangerous to leave the nest due to temperature, predators, etc... so they cannot feed and the collected food is needed for the young.
• Devouring Young. It not that the parent can't fly again. It that the young eat their parent, or practice self-defense on their parent. Particularly if the parent is injured by landing, or exhausted from hunger.
• The female lands to lay her eggs and rear her young because she senses she is close to dying. It is timed so that once the young fly away the female will succumb to old age a few days later. – MintySoftboi Nov 26 '19 at 12:41
• @MintySoftboi Yes, but why is it that she waits for old age? What about the birthing process could not be survived by doing so when she is younger? Is it that hard to obtain food? Is that landing on the ground a death sentence? Is it that laying the eggs itself renders her flightless? It not implausible that this life-cycle exists. You just need to explain why this life-cycle rather than say: laying eggs once a year? Nature rewards offspring that reproduce themselves. Two clutches give 2X opportunities for that. So why is 1X better? – Kain0_0 Nov 27 '19 at 22:14
• I would equate the middle limbs to that of a t-rex's arms. Early in development, they are proportionate to the rest of the body, but as the individual reaches maturity, they are only needed for basic grasping and are therefore useless for hold up their weight much less propelling them far enough to take off – MintySoftboi Nov 28 '19 at 2:05
• @MintySoftboi Interesting thought, that makes this creature similar to Quetzalcoatlus. Which has had research showing that it could plausibly launch itself using just its wings on level ground. – Kain0_0 Nov 28 '19 at 2:37
• @MintySoftboi - waiting for old age, or for impending mortality, before even trying to reproduce would seem to greatly up the likelihood that something would go wrong in the process and the female ends up with no (surviving) offspring... so waiting till the last minute would seem to be a very risky reproductive strategy. There are animals that have short life cycles, and some that don't survive past reproducing (salmon come to mind) but species waiting until they're already dying before even trying to reproduce still seems risky - especially for k-strategists whose offspring, need care. – Megha Dec 2 '19 at 2:45