UNIONDALE, N.Y. -- The Ottawa Senators had talked about avoiding a letdown after clinching a postseason berth.
The Islanders won for the fourth time in five games to stay alive in the Eastern Conference playoff race, scoring 17 goals in its last four games.
"Right now it seems we're clicking the way we want," said Biron, who won his third consecutive start. "We're frustrating teams, killing penalties and doing a lot of good things,"
Matt Cullen's close-range goal late in the third ended Biron's bid for his 27th career shutout. The loss snapped Ottawa's six-game win streak.
"They have some skill and they buried their chances," Senators assistant captain Mike Fisher said. "We weren't prepared enough."
The Senators remained seven points ahead of Montreal for fifth place with three games remaining. The Canadiens hosted Buffalo later.
New York came up empty on seven shots in the first period, but scored three goals on its first six shots in the second against goalie Brian Elliott.
Rookies Tavares and Reese scored exactly two minutes apart and second-year veteran Hillen added another to deflate a Senators club that fell four points behind New Jersey for fourth place in the East.
"We don't want to relax just because we're in a spot," Fisher said. "We've had a good run and we'll be ready and regroup."
Comeau opened the barrage on a 3-on-2 rush, setting up Tavares' high-slot goal 1:19 into the period.
Tavares scored for the first time in 17 games at Nassau Coliseum, ripping a shot into the top-right corner for his 22nd goal. Comeau has six points in his last three games.
Just two minutes later, Reese's right circle slap shot moved through traffic in front to beat Elliot. New York got another goal from a defenseman when Hillen's between-the-circles wrist shot beat Elliot high glove-side midway through the period for a 3-0 lead.
"We're not giving any points away," Tavares said. "When you're playing good hockey, you don't want to see the season end. At the same time, it will breed good things for next season."
Former Islander Chris Campoli nearly ended the shutout bid two minutes into the third before his point shot hit the right post and skipped away from the goal mouth.
Bergenheim redirected a point-blank rebound for his ninth goal at 4:13 for a four-goal edge. Tavares' primary assist gave the top overall pick 11 multipoint games this season.
"They are giving lots of teams fits right now," Ottawa senior Jason Spezza said. "We talked a lot before the game to make sure there wasn't going to be a letdown. But our effort wasn't as good as it's been."
Elliot allowed four goals on 33 shots for his first loss since March 18.
"He's been there for us and we didn't give him the support he needed," Ottawa coach Cory Clouston said.
Spezza had scored seven goals and 12 assists in his last 15 games against the Islanders but was held scoreless on three shots.
"We don't want to get used to losses like this. We want to be feeling good heading into the playoffs," Spezza said.
Ottawa D Andy Sutton was hit with a 10-minute misconduct penalty on his first trip to Long Island since New York traded him last month. ... Goal-scoring co-leader Milan Michalek (leg) and top-scoring defenseman Filip Kuba (lower body) were scratched by the Senators. ... Biron started consecutive games for the first time since Nov. 6. ... Trevor Gillies bloodied Ottawa defenseman Matt Carkner in a center-ice fight early in the final period. ... Huntington, N.Y., native Mike Mann won $30,000 toward a new car after successfully shooting a puck into a small opening during a second-intermission contest.