Polarornis was in all likelihood aquatic and fed on fish and large invertebrates, probably being an ecological equivalent of loons, grebes, or the Cretaceous Hesperornithes of the Northern Hemisphere.
Polarornis was probably a water-dwelling creature that consumed fish and other large invertebrates, potentially resembling aquatic birds like loons, grebes, or the Hesperornithes of the Northern Hemisphere.