Even before this season, these two had a history. They raced together during FE's second season at Virgin Racing, which turned out to be Vergne's sole campaign with the British team.
Things turned ugly at the Paris E-Prix in 2016 as they clashed on-track and Vergne endured a tough time at Virgin after a disagreement with its management at that season's race in Buenos Aires.
He was also still coming to terms with being removed from the Toro Rosso Formula One team at the end of 2014, and what that meant for his motorsport career.
"We were both put in some difficult situations by some decisions," says Bird. "It was a stressful environment for both of us, for different reasons."
Vergne found a new home with Techeetah ahead of FE's third season, and also took a stake in the Chinese team. All of Vergne's five FE race victories have come with the black-and-gold liveried, non-manufacturer-backed outfit.
"I'm [also now] a lot more settled -- private life, professional life," says Vergne. "Coming into Techeetah is what changed me. Being in both sides of the team, building the team and driver, really taught me to step back and look at what a team really wanted from a driver.
"I learnt a lot -- how to be inside a team with the mechanics with the engineers, up to which point you can push them, and to always be easy on them when it's time to be. It taught me massively."
Vergne was the favorite to become FE's fourth different title winner in four seasons
ahead of the New York finale as he held a 23-point lead over Bird -- almost as many points as the sport awards for a race win.
Adding to Vergne's advantage was the form of his rookie teammate Andre Lotterer and the Audi team.
Audi, with its drivers Lucas di Grassi and Daniel Abt, had been the overwhelming favorite heading into the season thanks to the efficiency of its powertrain and the overall speed it showed in testing.
Lotterer, a triple Le Mans winner who has just completed his first season in FE, joined Techeetah ahead of season four.
He had a tough start in Hong Kong and Marrakech, but then pushed Vergne hard for the win in Santiago -- actually hitting the rear of his teammate's car at one point -- and since April's Rome race hasn't finished out of the points.
The combination of Audi, Lotterer and regular podium contender Sebastien Buemi -- FE's most successful driver, who finished the season without a race win -- meant Bird still carried hopes of victory into the Brooklyn doubleheader despite Vergne's points advantage.
Audi left every team in its wake during the first race, with Vergne taking first place and Abt settling for second. Buemi came in third.
Vergne could only manage a fifth-placed finish, although it was an admirable result after the Techeetah drivers were thrown out of qualifying for exceeding the maximum permitted power and had to start at the back of the grid.
Bird came home in ninth.
Virgin's struggles with the elongated track heavily hampered Bird, who was nevertheless proud of what he and his team had achieved in season four.