It's still unknown who briefly portrayed Batman in the Birds Of Prey TV series. The Batman movie franchise was in flux in the early 2000s, following the box-office performance of 1997's Batman & Robin. Warner Bros mulled several ideas for rebooting the series, including a live-action take on Batman Beyond led by Keanu Reeves or a Wolfgang Petersen Batman Vs Superman movie set to star Colin Farrell as the former and Jude Law as the latter.
None of those projects ended up happening, with Christopher Nolan eventually recruited to helm Batman Begins in 2005. In the midst of this came 2002's Birds Of Prey show from The CW. This superheroine series takes place in New Gotham City years after Bruce Wayne retired as Batman, and follows the crimefighting adventures of his daughter Helena Kyle (AKA Huntress), Barbara Gordon's Oracle and Rachel Skarsten's telepath Dinah. It's also notable for featuring an early live-action take on Harley Quinn - played by Mia Sara - and Aaron Paul playing a small role in the first episode. The show remixed elements from both the comics and the live-action movies, but despite debuting to strong ratings, it was cancelled after one season as audience interest gradually waned.
The Birds Of Prey TV show is pretty cheesy and dated viewed through a modern lens, but it at least attempted to do something interesting with the mythology. Batman himself is never a major character in the series and is only depicted through brief flashbacks. Early trailers suggested the show itself was a direct spinoff of Batman Returns, as they used footage from Tim Burton's 1992 sequel. Those links were played down on the series itself, though the costumes of both Batman and Catwoman were very clearly influenced by Returns. One mystery surrounding the show is who exactly played Batman in these scenes.
Batman's performer went uncredited on Birds Of Prey, though for many years actor Bruce Thomas became linked to the part. Thomas played a very Tim Burton-inspired take on the Caped Crusader in a series of early 2000s OnStar adverts and in more recent years loaned his voice to Commissioner Gordon in animated movies like Batman: Hush. Thomas himself debunked the Birds Of Prey rumor he played Batman on an episode of The BatPodcast in 2014, and despite his efforts to correct this credit on IMDb, it's still there.
All of which begs the question of who played Batman on the Birds Of Prey TV series, which has yet to be revealed. Given the very limited role the hero plays on the show - which is basically a few poses - it was likely a stuntman but it's odd this remains a mystery nearly 20 years after the series debuted. Birds Of Prey still retains a cult following, with Ashley Scott and Dina Meyer briefly returning as Huntress and Oracle respectively on the Arrowverse "Crisis On Infinite Earths" crossover event.