Shares of Burger King ( BKC) were climbing 8% Thursday after the nation's No. 2 fast-food chain posted a 29% jump in earnings for the December quarter, with sales staying relatively strong amid a U.S. spending slowdown. For the second quarter ended Dec. 31, Burger King earned $29 million, or 36 cents a share, up from $38 million, or 28 cents a share, a year earlier. The per-share results topped analysts' average estimate of 32 cents, according to Thomson Financial. Revenue rose to $613 million from $559 million a year earlier, exceeding Wall Street's $597.1 million target. Same-store sales, or sales at stores open at least a year, jumped 4.5%. In the Canada and the U.S. -- where many food and retail outlets saw a significant slowdown this quarter -- same-store sales rose 4.2%. That helped ease some worries brought on by McDonald's ( MCD), which earlier this week said same-store sales were flat in December and up just 3.3% for the quarter. "We succeeded in a challenging macroeconomic environment with marketing initiatives that drove increased sales and traffic, robust international restaurant growth, and the profitability of our highly franchised business model," said Burger King CEO John Chidsey in a statement. The company also said the fiscal third quarter is "off to a great start," with strong traffic and same-store sales in January. Burger King said it expects to exceed its initial financial guidance for 2008, with earnings per share growth of more than 15% for the fiscal year. Shares of Burger King recently were up $1.86 to $26.02.