Pershing Square's Bill Ackman has a two aspirin kind of day

Noted stock picker William Ackman had a decidedly gloomy day on Thursday: Two of his most high-profile bets were moving fast, but in the wrong direction for the hedge fund manager and investors in his $12 billion Pershing Square Capital Management.

The day started with news that the shares of retailer J.C Penney Co Inc , in which Pershing Square is the largest investor, tumbled as much as 22 percent in the wake of disappointing earnings news. The shares closed down about 17 percent at $17.57.

The second blow came hours later when Herbalife Ltd - in which Ackman made a $1 billion bet its shares would fall to zero - invited two representatives of arch enemy Carl Icahn onto its board. The company's shares ended the day 7.6 percent higher at $40.29 after the announcement.

The one-two punch of bad news is particularly punishing for Ackman because Pershing Square manages a very concentrated portfolio with only a handful of stocks, far less than the average hedge fund.

To be sure, Ackman has other strong performers in his portfolio, including mall operator General Growth Properties Inc and Canadian Pacific Railway Ltd . But Herbalife and JCP are the names Ackman spends most of his time explaining and defending at public conferences and behind closed doors to his own investors.

Coming at the month's end, the surging and swooning surely took a bite out of his fund's performance just as competitors were tallying their final numbers. Like his rivals, Ackman started 2013 on a strong note with a roughly 4 percent gain in January topped off by a roughly 0.9 percent rise in February, people familiar with his numbers said.

Clearly, the day's developments were not something the usually chatty Ackman was ready to discuss - at least in public. Telephone calls and emails, which the manager often returns immediately, went ignored as a day one associate described as "crazy" dragged on.

So far, Ackman's own investors have shown no signs of abandoning the fund manager, even as some have expressed concern in private that he has been so public about Herbalife.

However, the day's price moves are bound to rankle the ultra competitive manager just as he is trying to raise new capital.

(Reporting By Svea Herbst-Bayliss. Editing by Andre Grenon)