Bird Anatomy

Breast should be acceptable. I can't remember the last time I heard an experienced English-speaking birder use "chest" for that region of a bird's anatomy, if ever. The term "breast" is used in the "parts of a bird" diagrams in e.g. Harrison's seabird guide; Hayman, Marchant and Prater's shorebird guide; the woodpecker guide by Winkler et al; "Birds of Europe" by Mullarney et al; all major North American field guides (Sibley's, Kaufman's, Peterson's, and National Geographic Society); ad infinitum.