Influence of food and water availability on undirected singing and energetic status in adult male zebra finches (Taeniopygia guttata).

The songs of adult male zebra finches are termed "directed" and "undirected," depending on the social context in which they occur. Females elicit directed song, whereas undirected song is not addressed to a particular conspecific and even occurs at high levels in social isolation. We tested the hypothesis that the production of undirected song is more sensitive to a brief period of food deprivation than a comparable period of water deprivation. The hypothesis was based on prior findings suggesting that song production is energetically expensive and that food deprivation constitutes a more serious energetic challenge to zebra finches than does water deprivation. Two days of food or water deprivation were imposed on several groups of birds that provided song production data and a variety of energetic measures; normative data obtained in a baseline period when food and water were available ad libitum provided a standard for comparison. Singing, which occurred exclusively in the light phase of the day, was reduced at the onset of food deprivation, ceased completely within 4 h, and did not occur at all on the second day. When water was removed, the birds showed a slower and less substantial reduction in daily song production across the 2 days of deprivation. Energetic measures indicated that food deprivation was a greater energetic challenge than water deprivation. Our results demonstrate that undirected song in zebra finches is sensitive to nonsocial environmental factors that pose an energetic challenge and raise new questions about how birds calibrate their level of song production to the availability of nutrients in the environment.