It's an exciting and heartbreaking time to be a bird nerd . A birdwatcher, or a birder, if you will. Avian critters are migrating, which means we get to see rare breeds on their journeys to a warmer climate. But there have been some obstacles in their way, especially in urban areas such as New York City . You see, birds and skyscrapers don't get along. They fly into the crystal-clear glass windows of luxury condos and office buildings, and often die from the impact. Cheerful, huh? That's on top…