Final answer:
The essay uses a compare and contrast text structure to explore the similarities and differences between osprey and bald eagle species.
Step-by-step explanation:
The text structure of the essay where Dr. Messer explains the similarities and differences between an osprey and a bald eagle is a compare and contrast structure. This structure is evident because the essay focuses on describing both the similarities and discrepancies in characteristics such as migration, feeding, and mating habits between the two bird species. Within the compare and contrast structure, the essay may also utilize other strategies like classification and division to organize information more clearly, but the overarching structure remains focused on comparing and contrasting the two species.