When the blurry image on the screen sharpened to reveal a mother penguin sitting on her nest, the kindergartners couldn’t contain their excitement. Though the penguin and children were separated by more than 8,800 miles, the bird met their shrieks with a squawk of alarm. Nearly 100 kindergarten students at Mount Vernon Exploratory School were able to “visit” a penguin rookery on Ross Island, a small active volcanic island off the Antarctic coast through Skype, a video-call service.