Sugar concentration and the structure of the sunbird's song

Summary The full song of the yellow-bellied sunbird (Nectarinia venusta) comprises distinct phrases, which retain their typical three-part structure and temporal organization regardless of the concentration of the sucrose solution provided. However, the sugar concentration does affect the types of elements that make up the initial part of the phrase and the number of elements in the terminal part. Several types of elements may be produced either as separate calls or as components of the initial part of the phrase; as the concentration decreases, at least two of these element types occur progressively more often in the phrases, taking the place of others.