They may not have the gravitas of bald eagles or the mysterious allure of condors, but North America's ducks -- a classic harbinger every year of the changing seasons -- have done something remarkable. Scientists say the number of mallards, teals, canvasbacks and other ducks this year has reached the highest level ever recorded, with a total estimate of 48.6 million breeding ducks in Canada and the United States. The number is 7 percent higher than last year, according to a survey released this week from the U.S. Fish and Wildlife Service, and 43 percent higher than the historic average...