Data from: Declining food availability alters vocal behavior of a nomadic finch

Social information (i.e., gathered from other individuals) can be an
important information source for animal decision-making related to
foraging and movement. For instance, social information in the form of
acoustic cues can be used to locate food sources. The ability to
accurately assess declines in food availability or quality in order to
make movement decisions can also impact fitness. However, little is known
about whether the acoustic cues produced by animals differ when food is in
decline and could therefore be used as a source of information in this
context. To test this hypothesis, we conducted a study on the effect of
food availability on the vocal behavior of pine siskin (Spinus pinus).
Pine siskins are gregarious, nomadic finches that feed on seeds that
fluctuate irregularly and dramatically in abundance. We recorded and
characterized the vocalizations of wild-caught birds in captivity under
two experimental conditions: unlimited food and a 20% reduction in food
availability. Birds called more frequently when food restricted and
increased the production of two specific call types (Types B and C). For
both of these call types, the minimum frequency was higher when birds were
food restricted, and for C calls the median, peak dominant, and peak
fundamental frequencies were also higher. We further tested whether
changes in acoustic frequency were associated with circulating
corticosterone levels, as is predicted by the hypothesis that circulating
glucocorticoid levels mediate changes in acoustic frequency in response to
food restriction, and found only limited evidence to support the
hypothesis.