The Hughes 500C that "Walker" flew throughout the film is one of the few turbine-engine helicopters (worldwide) which is flown single-pilot from the left seat. Since people tend to scan visually from left to right... the same way they read a book... it was more effective to have Walker in a left-facing helicopter like the 500C, as opposed to say, a Bell JetRanger, or a Fairchild FH-1100 which are flown from the right seat. Director William A. Graham shot all of the close-ups from the left side of the ship, usually looking slightly upward, with a tight depth-of-field. This threw everything behind Walker's shoulders out of focus. However, this was a dual-control ship! Note particularly the take-off after Walker fueled-up from the tanker truck. If you look closely (despite the fuzzy focus) you can readily see that the right-seat position looks unusually lumpy. That's because the film pilot who was doing the actual flying, was crouched in there, under a black shroud.
According to the stunt pilot on the film, David Janssen did some of his own flying in this movie. "A favorite project of [pilot Jim] Gavin's was the 1973 made-for-TV movie titled Birds of Prey. It starred David Janssen as a traffic reporter who discovers a bank robbery. 'Birds was a ground-breaking project,' he says. 'We took the helicopter out of its normal environment, put it in the city streets and did all the work with Janssen in flight for real. In fact, since he was a pilot Janssen did a lot of the flying, and I'd sit opposite him.' (Flying Magazine, June 1988, p. 30)
The robber's helicopter is an Aérospatiale SA 315B Lama as shown by the old FAA registration number N13583 displayed in the movie . The SA 315B is a French single-engined helicopter combining the Alouette II airframe with Alouette III components and powerplant to meet hot and high operational requirements of the Indian Armed Forces.
Because of copyright issues, the now rare DVD had to replace jazz songs with lyrics with jazz instrumentals. This explains David Janssen's singing along with songs that have no words.