Your field guide can be a one-day project, a semester-long project, a year-long project, or a multi-year project. You can schedule schoolyard observations weekly, biweekly, or monthly. The more time you invest, the more opportunities you present for students to learn and participate. The time you need is a direct correlation to the time you can invest. But even a one-day project should be revisited once a season. As birds and other animals move and migrate, as plants blossom and trees drop their leaves, your students will have the opportunity to observe seasonal changes.