Genellan Planetfall

Genellan -- beautiful, Earthlike world where intelligent cliff-dwellers waited in fear for the day the warlike bear people would return...
Genellan -- the only refuge for a ship's crew and a detachment of spacer marines, abandoned by a fleet fleeing from alien attackers.
Stranded on Genellan, the humans struggled to make a home for themselves until -- they hoped against hope -- the fleet could rescue them. Lt. Sharl Buccari tried desperately to hold on to the threads of command over both the civilians and the marines -- to keep her people together.
Winter was coming. No one knew if the winged natives would be friend or foe. And now the bear people were returning, bent on destroying every human -- but not before stealing the secret of hyperlight drive, the key to interstellar flight...