Sterling Financial Corp. (Nasdaq: STSA), parent company of Sonoma Bank, now known as Argent Bank, reported third-quarter net income decreased 31.4 percent, attributed to a dip in mortgage banking activity and one-time merger expenses.

Sterling reported net income of $21 million for the three-month period ended Sept. 30, down from $30.6 million a year before.

That income -- representing 33 cents per share -- reflected reduced mortgage banking activity and one-time expenses related to the company's merger with Umpqua Holdings Corp., parent of Umpqua Bank, according to Sterling.

Sterling's loan portfolio grew by 17.2 percent over 12 months to $7 billion. Net interest income was $82.5 million, up 9.6 percent from a year before.

The merger with Umpqua is expected to be complete in the first half of 2014.