Diomedes

See here.

Large flying animals evolved in the dense Diomedean atmosphere. Flocks of intelligent Diomedeans winter in the tropics. The exertion of a long flight causes hormonal changes so that, upon arrival, there is a mating orgy. Females are pregnant when they return home in spring and give birth before the next migration when parents carry infants who can fly independently the following year.

Towns, vacated every autumn but reoccupied every spring, are centers of stone working, ceramics, carpentry and limited agriculture although the main economic activities are hunting and herding. The Great Flock of Lannach is indolent, artistic, ceremonious and matrilineal whereas Diomedeans of the Fleet of Drak'ho have abandoned annual migration in favor of fishing and seaweed harvesting from large, oceangoing rafts where the exertion of navigational activities exercises the body, maintaining year-round sexuality and reproduction and patriarchal monogamy. The Fleet, able to accumulate stores, machines and books, is richer but authoritarian.

On Starkad (see here), land-dwelling and sea-dwelling intelligent species were natural enemies. On Diomedes, Flock and Fleet are the same species but initially regard each other with mutual horror although extra-planetary traders encourage tolerance and cooperation. In the Imperial period, Drak'ho can adapt to living on land and to engaging in new economic activities whereas the migratory Lannachska culture, used to summer time indolence, cannot survive the introduction of high-energy technology but, without it, must remain poor and powerless.