The Bills are trying to finalize a new contract with Jackson, according to the sources. He is scheduled to make $4 million this season, and a source told ESPN NFL Insider John Clayton that he's been willing to adjust his salary if he can find a new team.
Jackson, a second-round pick of the Minnesota Vikings in 2006, spent last year with the Seahawks, starting 14 games.
Wilson was named the team's starting quarterback on Sunday night by coach Pete Carrolll. The rookie threw for 185 yards and two touchdowns in a 44-14 rout of the Kansas City Chiefs on Saturday night. He also scrambled for 58 yards while leading the Seahawks to scores on their first six possessions.
"He's done everything we've asked of him," Carroll said after Saturday's game. "This is the guy we hoped he would be. All of the talk about how tall he is and all that stuff, I don't see it being a factor. I don't see it, and I have watched more carefully than anybody could ever have watched, and I don't see it being an issue. It isn't to me."
Jackson sat out the Seahawks' first two preseason games, before getting his first action taking over for Wilson in the second half Saturday.
And Jackson served as the backup in part because Flynn missed the game due to a sore elbow.
The Bills, meanwhile, have Ryan Fitzpatrick entrenched as their No. 1 quarterback after signing him to a six-year, $59 million extension last season. Vince Young and Tyler Thigpen have been vying for the backup job this preseason, and coach Chan Gailey has maintained that there's only room for one backup, because the No. 3 job is going to receiver/Wildcat specialist Brad Smith.
Young signed a one-year, $2 million deal with the Bills in May, after spending last season with the Philadelphia Eagles.
He had the edge to win the No. 2 job until he struggled in a 38-7 loss to Pittsburgh on Saturday. Young threw two interceptions, the first coming on his first pass attempt, and finished 12 of 26 for 103 yards in playing the entire second half.
Jackson had an up-and-down five-year career with the Vikings, His most productive season came in 2007, when he started 12 games.
He signed a two-year contract with the Seahawks last year, and was credited for playing a major role in the team's turnaround after a 2-6 start. He posted career numbers in completions (271) and attempts (450) to go with 3,091 yards passing with 14 touchdowns and 13 interceptions.
Jackson also earned plenty of support among his teammates after playing most of the season with a painful pectoral injury.
Jackson has had his faults, with much of the criticism focusing in on his decision-making and holding onto the ball too long.
There were also times he faltered in the fourth quarter -- including late-season home losses to Washington and San Francisco -- which contributed to costing the Seahawks a shot at a playoff berth.
Information from ESPN NFL Insider John Clayton and The Associated Press was used in this report.