NEW YORK (Reuters) - M&T Bank Corp (MTB.N), the first large U.S. bank to report fourth-quarter results, said on Monday that profit tumbled 70 percent, hurt by debt write-downs and turmoil in residential real estate markets.

The bank, which counts Warren Buffett's Berkshire Hathaway Inc (BRKa.N) (BRKb.N) among its largest investors, said net income fell to $64.9 million, or 60 cents per share, from $213.3 million, or $1.88, a year earlier. Operating profit totaled 77 cents per share, the bank said.

Analysts on average expected profit of $1.85 per share, according to Reuters Estimates. Buffalo, New York-based M&T was one of the few large U.S. banks that had not in the last two months specifically cautioned investors how credit and mortgage market turmoil would hurt fourth-quarter results.

M&T shares fell $3.24, or 4.4 percent, to $70.51 in pre-market electronic trading.

The company reduced profit by $78 million, or 71 cents per share, to write down collateralized debt obligations, and by $29 million, or 27 cents per share, for credit losses.

Earnings were also reduced 13 cents per share for M&T's share of antitrust litigation involving credit card network Visa Inc, and 8 cents per share for acquisitions.

M&T Bank said it has $64.9 billion in assets and more than 650 branches in seven mid-Atlantic states and Washington, D.C.

Its results may foreshadow those at other large U.S. banks, most of which are to report by the middle of next week. Nearly all are expected to report lower profits, or losses.

Berkshire owned a roughly 6.3 percent stake in M&T Bank as of Sept 30, according to Thomson ShareWatch. Only Allied Irish Banks Plc (ALBK.I) (ALBK.L) and M&T Bank Chief Executive Robert Wilmers held larger stakes, Thomson ShareWatch said.

M&T Bank shares closed Friday at $73.75 on the New York Stock Exchange. The shares have fallen 38 percent in the last year, compared with a 28 percent drop in the Philadelphia KBW Bank Index (.BKX).

(Reporting by Jonathan Stempel; Editing by Dave Zimmerman)