Commercial banks regained their affection for mortgage securities, adding nearly $43.00 billion to their aggregate holdings of single-family MBS in the first quarter. Recently released data from the Federal Deposit Insurance Corp. show commercial banks held a record $940.04 billion of mortgage-backed securities on their books at the end of March. That was up 4.8 percent from the end of 2005 – a year in which banks generally let their MBS holdings decline. … [One data table included]