Motifs are recurring structures, contrasts, and literary devices that can help to develop and inform the text’s major themes.

Similarities Between Dinosaurs and Birds

Much of the foreshadowing early in the novel revolves around the concept that dinosaurs are related to birds. At first, Crichton merely hints at the concept: the injured InGen worker uses the word "raptor", which Manuel associated with the mythical Costa Rican hupia. Bobbie looks up the word in two dictionaries and finds the definitions "abductor" and "bird of prey." Furthermore, Tina states that the lizard tracks she saw before she was attacked looked like bird tracks, and claims that the lizard chirped and bobbed its head like a chicken. This bird imagery continues after the discussions of dinosaurs begin. Morris says that Grant's dinosaur fossils look like chicken bones, and Grant describes the procompsognathus as being roughly the size of a chicken and the velociraptor as "finely tuned as a bird."

The reason for these comparisons becomes more obvious once Grant and company begin interacting with the dinosaurs on Isla Nublar. Even from their first observations of the animals, Grant and Sattler are immediately surprised at how deftly the dinosaurs move. The velociraptors are given particularly birdlike descriptive features, a connection that emphasizes that dinosaurs were not necessarily the lumbering beasts they are often depicted as today. Rather, Crichton explores paleontologists' theories that dinosaurs may have been exceptionally agile and intelligent creatures.

Around the time Crichton wrote Jurassic Park, the latest scientific research was leaning toward a possibly closer relationship between birds and dinosaurs than paleontologists had previously thought. At the time the idea was still somewhat controversial. Since the book's publication, however, virtually irrefutable fossil evidence has been found linking the heritage of birds to dinosaurs. Nevertheless, many paleontologists have found the depiction of some of the dinosaurs in the movie version of Jurassic Park—the screenplay of which was partially written by Crichton himself—to be exaggerated and unrealistic, the velociraptors in particular being much too large and speedy. Nonetheless, this more recent research seems to have borne out the idea that dinosaurs, as ancestors of both modern-day lizards and birds, were more agile than previously thought.