John W Campbell answered the question and Anderson adapted Campbell's answer as the flying, intelligent Ythrians. More generally, could there be intelligent beings whose bodies were completely at home in wind, rain, storm and sea without needing clothes or buildings? They would need to have some level of technology and limbs for manipulation as well as locomotion. They might have bypassed or superseded urban civilization? Such beings might synthesize the best features of animality and rationality.
-copied from here.
Ythrians are definitely more at home in the elements than human beings:
"Eyath left the crag whereon she had perched the last few hours, after she could breast the weather no more. She was cold, wet, stiff at first. But the air blew keen into nostrils and antlibranchs, blood awoke, soon muscles were athrob." (Rise Of The Terran Empire, p. 606)
Eyath mourns alone. Before that, Rochefort and Tabitha had looked for her:
"'Where is she?' His voice was raw.
"'Alone,' she answered.
"'In this weather? When it's likely to worsen?'" (p. 602)
When Eyath left the crag:
"The sea laughed but the island dreamed..." (p. 606)
We have previously discussed this use of the word "dreamed."