Egg prices are rising once more as a lingering outbreak of bird flu coincides with the high demand of the holiday baking season. But prices are still far from the recent peak they reached almost two years ago. And the American Egg Board, a trade group, says egg shortages at grocery stores have been isolated and temporary so far. “Those are being rapidly corrected, sometimes within a day,” said Emily Metz, the Egg Board’s president and chief executive officer. The average price for a dozen eggs in U.S.