Volunteers for Operation RubyThroat observe hummingbird migration and/or nesting behavior and share information with peers across North and Central America. The resulting data on hummingbird behavior and distribution are submitted to a central clearing house, analyzed, and then disseminated to scientists through the Operation RubyThroat website. Ruby-throated Hummingbirds (Archilochus colubris) are the most widely distributed of the 339 species of hummingbirds, occurring in all ten countries of North and Central America. They come frequently to nectar plants and backyard sugar water feeders and are easily observed. Nonetheless, many aspects of the birds’ natural history are not well understood. Through EarthTrek, Operation RubyThroat seeks data about two aspects of Ruby-throated Hummingbird behavior: 1) timing of migration; and 2) nesting. In addition to providing much-needed baseline information, your data may help show whether these birds’ behaviors are changing, perhaps due to external factors such as climate change, alteration of habitat, and other factors.