U.S. builders began work on slightly fewer homes in February, but they started preparing for what could be the healthiest spring buying season since the housing bubble burst more than five years ago, the government reported Tuesday. The Commerce Department said housing starts fell 1.1 percent last month to an annual rate of 698,000 units. But building permits - a gauge of future activity - jumped 5.1 percent in February to the highest level in more than a year. Construction of single-family homes, which comprises about 70 percent of housing starts, fell last month to an annual rate of 457,000 after rising for four consecutive months to an 18-month high in January. A jump in volatile apartment construction offset the decline. A mild winter in most of the United States allowed builders to continue working throughout the season, and an improving job market has many builders slightly more optimistic about home sales this year.