A 2006 paper (Slack et al.) on earliest Paleocene penguin (Waimanu manneringi) fossils finds sheds light on early bird diversification and possible decline of the pterosaurs (reduction to only large taxa).
Penguins and storks
According to Slack et al., penguins and storks nest together closer than loons and albatross + petrel. And they must have diversified at 67.1 mya, prior to the K/T extinction.
Falcons and pterosaurs
An earlier diversification, 77.2 mya marked the splitting of the falconiformes from the sea birds (including the above listed taxa). That means falcons or protofalcons were soaring over Late Cretaceous skies. Noting trends for ever larger pterosaurs and the absence smaller pterosaurs in the Late Cretaceous, the authors report, “Kim et al. (2003) offer the interpretation that pterosaurs might have fed on small birds—equally plausible to us, however, is that the raptors (Falconiformes) could have preyed on young pterosaurs.”
Never heard that one before. Of course, if a predator eats all of its prey, the predator also dies. So, improbable, but interesting.
Kim CB, Huh M, Cheong CS, Lockley MG and Chang HW 2003. Age of the pterosaur and web-footed bird tracks associated with dinosaur footprints from South Korea. Island Arc 12:125–131.
Slack KE, Jones CM, Ando T Harrison GL, Fordyce RE Arnason U and Penny D 2006. Early Penguin Fossils, Plus Mitochondrial Genomes, Calibrate Avian Evolution. Mol. Biol. Evol. 23(6):1144–1155.