The oak trees are laden with catkins right now, and those, in turn, are filled with a variety of caterpillars. These neat little packets of protein are great sources of energy for birds that are swinging by on a longer migration from the tropics to more northern nesting sites. Many warblers, including Yellow-Throated and American Redstarts, are just filling up on their way. You might also see White-eyed vireos, Blue-headed Vireos, and Summer Tanagers.