Shirley and Jeffrey Caldwell don’t fashion themselves professional birdwatchers, but they dabble. “We just watch out the window, and we have some feeders,” Shirley told NBC News. But they know enough ...

ERIE, Pa. – Longtime birder Jamie Hill knew he'd come across something rare. The Waterford, Pennsylvania, man saw a northern cardinal that appeared to be male on its right side and female on its left.

A birdwatching couple in northwestern Pennsylvania has documented one of nature's most rare and elusive occurrences. Jeffrey and Shirley Caldwell, two experienced birdwatchers based in Erie, lured of ...

Thanks to the developmental fusion of male-female bird twins into one individual, this northern cardinal is half red and half tan -- split lengthwise down its middle -- and is half male and half ...