In TOS, Klingons had battlecruisers, and Romulans had birds of prey. Ship names at that time seemed pretty simple and clear cut. Then, in Star Trek 3, where the Klingon Bird of Prey was introduced, both Romulans and Klingons now had Birds of Prey. This was confusing for some, as how could both Klingons and Romulans have Birds of Prey, but was explained partially in apocrypha that the original Star Trek 3 script stated the Klingon ship was actually a stolen Romulan prototype, and the name was just a holdover (hence it having bird markings, just like the Romulan counterpart). Not to mention the Enterprise Incident in TOS establishes that at least once, the Klingons and Romulans shared technology.
TNG then introduced us to the Romulan Warbird, the D'Deridex class, which happened to be green, just like the Klingon Bird of Prey, and seemed to incorporate some hint of Klingon design, rather than the classic Romulan BOP saucer design.
In Nemesis, it was revealed that Remans had their own version of the Warbird, the Scimitar, not to mention the Romulans had a new Valdore Class warbird, which in many ways resembles a scaled up Klingon BOP or Battle cruiser.
Then came Enterprise, and later Star Trek 2009, where Klingon Battlecruisers were referred to as Warbirds, further confusing issues. Braga had explained the use of the term Warbird for Klingon ships in Broken Bow as a writing error, and Abrams presumably was using the term to follow Enterprise continuity.
So those are the real world explanations of why Both Romulans and Klingons have Birds of Prey, and Romulans, Remans, Klingons have Warbirds. But what is the in-universe explanation? Is it because Starfleet confused Klingon and Romulan ships at one point? Or is it because they classify all enemy battle cruisers as Warbirds and all enemy destroyer class ships as Birds of Prey? Or are these names reflective of the Klingon-Romulan alliance, where both sides shared technology?
TNG then introduced us to the Romulan Warbird, the D'Deridex class, which happened to be green, just like the Klingon Bird of Prey, and seemed to incorporate some hint of Klingon design, rather than the classic Romulan BOP saucer design.
In Nemesis, it was revealed that Remans had their own version of the Warbird, the Scimitar, not to mention the Romulans had a new Valdore Class warbird, which in many ways resembles a scaled up Klingon BOP or Battle cruiser.
Then came Enterprise, and later Star Trek 2009, where Klingon Battlecruisers were referred to as Warbirds, further confusing issues. Braga had explained the use of the term Warbird for Klingon ships in Broken Bow as a writing error, and Abrams presumably was using the term to follow Enterprise continuity.
So those are the real world explanations of why Both Romulans and Klingons have Birds of Prey, and Romulans, Remans, Klingons have Warbirds. But what is the in-universe explanation? Is it because Starfleet confused Klingon and Romulan ships at one point? Or is it because they classify all enemy battle cruisers as Warbirds and all enemy destroyer class ships as Birds of Prey? Or are these names reflective of the Klingon-Romulan alliance, where both sides shared technology?
