title: Studying individual interactions and direct fitness benefits in wild birds: history and practice.
authors: Harvard University, Cambridge, MA, USA. berg2@fas.harvard.edu
authors: Elena C
authors: EC
authors: Berg
authors: Dean A
authors: DA
authors: Williams
mesh_terms: D000533:Altruism; D000818:Animals; D001522:Behavior, Animal; D001717:Birds; D003299:Cooperative Behavior; D004463:Ecology; D006379:Helping Behavior; D012098:Reproduction; D012726:Sexual Behavior, Animal