The Bird-of-Prey was a military vessel used by the Romulan Star Empire throughout the 23rd century. The first Bird-of-Prey to be encountered by the Federation Starfleet was in 2266, when a single Bird-of-Prey attacked several outposts bordering the Romulan Neutral Zone. A fast and deadly class equipped with cloaking capabilities, Romulans often used Birds-of-Prey to patrol the Neutral Zone and ambush any starship that wandered too close.
As portrayed in Star Trek: The Original Series - "Balance of Terror" (TV, 1966)
The Romulan Bird-of-Prey model, first created for the episode “Balance of Terror,” was designed and built by Wah Chang. The 2.5 foot model was constructed of vacuum-formed plastic, plaster, and metal and featured internal lighting details. The model was repainted following Chang’s initial delivery and given the iconic bird graphic featured prominently on its ventral hull.
This model was inadvertently destroyed after filming “Balance of Terror”, and so the Bird-of-Prey seen in the second season episode “The Deadly Years” used reused footage of the model from “Balance of Terror”. In the show’s third season episode “The Enterprise Incident”, since the Bird-of-Prey model was no longer available and, in an effort to get more use out of the newly designed and constructed Klingon battle cruiser model, the Romulans were shown to be using the distinctly different Klingon design. The iconic design of the original Bird-of-Prey would later influence the designs of the Romulan Birds-of-Prey seen in Star Trek: Enterprise and Star Trek: Picard.