Angelique Kerber smiled and waved her arms like an orchestra conductor as the Rod Laver Arena crowd sang “Happy Birthday” after her 6-2, 6-7 , 6-2 second-round win on Wednesday at the Australian Open. The defending champion wasn’t completely on song on her 29th birthday, angrily swiping her racket in the second set in a burst of frustration that momentarily threw her off her game – and allowed Carina Witthoeft back into the match.